Anatomy at a Glance

Omar Faiz

David Moffat

Blackwell Science

Anatomy at a Glance

OMAR FAIZ

BSc (Hons), FRCS(Eng)

Specialist Registrar in General Surgery

DAVID MOFFAT

VRD, MD, FRCS

Emeritus Professor of Anatomy

University of Cardiff

Blackwell

Science

AAAA01 21/5/05 10:34 AM Page 1

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First published 2002 by Blackwell Science Ltd

Reprinted 2002

Library of Congress Cataloging-in-Publication Data

Faiz, Omar.

Anatomy at a glance / Omar Faiz, David Moffat

p. cm.

Includes index.

ISBN 0-632-05934-6 (pbk.)

1. Human anatomy —Outlines, syllabi, etc. I. Moffat, David, MD. II. Title.

[DNLM: 1: Anatomy. QS 4 F175a 2002]

QM31 .F33 2002

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ISBN 0-632-05934-6

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Contents 3

Preface, 5

The thorax

1 The thoracic wall I, 6

2 The thoracic wall II, 8

3 The mediastinum Iathe contents of the

mediastinum, 10

4 The mediastinum IIathe vessels of the thorax, 12

5 The pleura and airways, 14

6 The lungs, 16

7 The heart I, 18

8 The heart II, 22

9 The nerves of the thorax, 24

10 Surface anatomy of the thorax, 26

The abdomen and pelvis

11 The abdominal wall, 28

12 The arteries of the abdomen, 31

13 The veins and lymphatics of the abdomen, 34

14 The peritoneum, 36

15 The upper gastrointestinal tract I, 38

16 The upper gastrointestinal tract II, 40

17 The lower gastrointestinal tract, 42

18 The liver, gall-bladder and biliary tree, 44

19 The pancreas and spleen, 46

20 The posterior abdominal wall, 48

21 The nerves of the abdomen, 50

22 Surface anatomy of the abdomen, 52

23 The pelvis Iathe bony and ligamentous pelvis, 54

24 The pelvis IIathe contents of the pelvis, 56

25 The perineum, 58

26 The pelvic viscera, 60

The upper limb

27 The osteology of the upper limb, 62

28 Arteries of the upper limb, 66

29 The venous and lymphatic drainage of the upper limb and the

breast, 68

30 Nerves of the upper limb I, 70

31 Nerves of the upper limb II, 72

32 The pectoral and scapular regions, 74

33 The axilla, 76

34 The shoulder (gleno-humeral) joint, 78

35 The arm, 80

36 The elbow joint and cubital fossa, 82

37 The forearm, 84

38 The carpal tunnel and joints of the wrist and hand, 86

39 The hand, 88

40 Surface anatomy of the upper limb, 90

The lower limb

41 The osteology of the lower limb, 92

42 The arteries of the lower limb, 94

43 The veins and lymphatics of the lower limb, 96

44 The nerves of the lower limb I, 98

45 The nerves of the lower limb II, 100

46 The hip joint and gluteal region, 102

47 The thigh, 106

48 The knee joint and popliteal fossa, 109

49 The leg, 112

50 The ankle and foot I, 114

51 The ankle and foot II, 116

52 Surface anatomy of the lower limb, 118

The autonomic nervous system

53 The autonomic nervous system, 120

The head and neck

54 The skull I, 122

55 The skull II, 124

56 Spinal nerves and cranial nerves I–IV, 126

57 The trigeminal nerve (V), 128

58 Cranial nerves VI–XII, 130

59 The arteries I, 132

60 The arteries II and the veins, 134

61 Anterior and posterior triangles, 136

62 The pharynx and larynx, 138

63 The root of the neck, 140

64 The oesophagus and trachea and the thyroid gland, 142

65 The upper part of the neck and the submandibular

region, 144

66 The mouth, palate and nose, 146

67 The face and scalp, 148

68 The cranial cavity, 152

69 The orbit and eyeball, 154

70 The ear, and lymphatics and surface anatomy of the head and

neck, 156

The spine and spinal cord

71 The spine, 158

72 The spinal cord, 160

Muscle index, 162

Index, 168

Contents

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The study of anatomy has changed enormously in the last few decades.

No longer do medical students have to spend long hours in the dissect-

ing room searching fruitlessly for the otic ganglion or tracing the small

arteries that form the anastomosis round the elbow joint. They now

need to know only the basic essentials of anatomy with particular

emphasis on their clinical relevance and this is a change that is long

overdue. However, students still have examinations to pass and in this

book the authors, a surgeon and an anatomist, have tried to provide a

means of rapid revision without any frills. To this end, the book follows

the standard format of the at a Glanceseries and is arranged in short,

easily digested chapters, written largely in note form, with the appro-

priate illustrations on the facing page. Where necessary, clinical appli-

cations are included in italics and there are a number of clinical

illustrations. We thus hope that this book will be helpful in revising and

consolidating the knowledge that has been gained from the dissecting

room and from more detailed and explanatory textbooks.

The anatomical drawings are the work of Jane Fallows, with help

from Roger Hulley, who has transformed our rough sketches into the

finished pages of illustrations that form such an important part of the

book and we should like to thank her for her patience and skill in carry-

ing out this onerous task. Some of the drawings have been borrowed or

adapted from Professor Harold Ellis’s superb book Clinical Anatomy

(9th edn) and we are most grateful to him for his permission to do this.

We should also like to thank Dr Mike Benjamin of Cardiff University

for the surface anatomy photographs. Finally, it is a pleasure to thank

all the staff at Blackwell Science who have had a hand in the prepara-

tion of this book, particularly Fiona Goodgame and Jonathan Rowley.

Omar Faiz

David Moffat

Preface 5

Preface

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6 Thorax

1 The thoracic wall I

Cervical

rib

Scalenus

Brachial

plexus

Subclavian

artery

Subcostal groove

Tubercle

Neck

Head

Facet for

vertebral body

First rib

Thoracic outlet (inlet)

Suprasternal notch

Manubrium

Third rib

Body of sternum

Intercostal

space

Xiphisternum

Costal cartilage

Floating ribs

Angle

Sternocostal

joint

6th

rib

Costochondral

joint

Shaft

Fig.1.2

A typical rib

Fig.1.1

The thoracic cage. The outlet (inlet)

of the thorax is outlined

Fig.1.4

Joints of the thoracic cage

Fig.1.3

Bilateral cervical ribs.

On the right side the brachial plexus

is shown arching over the rib and

stretching its lowest trunk

Demifacet for head of rib

Transverse process with

facet for rib tubercle

Costovertebral

joint

Costochondral joint

Sternocostal joint

Interchondral joint

Xiphisternal joint

Manubriosternal joint

(angle of Louis)

Clavicle

Costal margin

Costotransverse

joint

AAAC01 21/5/05 10:38 AM Page 6

The thoracic cage

The thoracic cage is formed by the sternum and costal cartilages in

front, the vertebral column behind and the ribs and intercostal spaces

laterally.

It is separated from the abdominal cavity by the diaphragm and com-

municates superiorly with the root of the neck through the thoracic

inlet(Fig. 1.1).

The ribs (Fig. 1.1)

• Of the 12 pairs of ribs the ﬁrst seven articulate with the vertebrae pos-

teriorly and with the sternum anteriorly by way of the costal cartilages

(true ribs).

• The cartilages of the 8th, 9th and 10th ribs articulate with the carti-

lages of the ribs above (false ribs).

• The 11th and 12th ribs are termed ‘ﬂoating’ because they do not articu-

late anteriorly (false ribs).

Typical ribs (3rd–9th)

These comprise the following features (Fig. 1.2):

•A headwhich bears two demifacets for articulation with the bodies

of: the numerically corresponding vertebra, and the vertebra above

(Fig. 1.4).

•A tubercle which comprises a rough non-articulating lateral facet as

well as a smooth medial facet. The latter articulates with the transverse

process of the corresponding vertebra (Fig. 1.4).

•A subcostal groove: the hollow on the inferior inner aspect of the

shaft which accommodates the intercostal neurovascular structures.

Atypical ribs (1st, 2nd, 10th, 11th, 12th)

• The 1st rib (see Fig. 63.2) is short, ﬂat and sharply curved. The head

bears a single facet for articulation. A prominent tubercle (scalene

tubercle)on the inner border of the upper surface represents the inser-

tion site for scalenus anterior. The subclavian vein passes over the 1st

rib anterior to this tubercle whereas the subclavian artery and lowest

trunk of the brachial plexus pass posteriorly.

A cervical rib is a rare ‘extra’ rib which articulates with C7 poster-

iorly and the 1st rib anteriorly. A neurological deﬁcit as well as vascu-

lar insufﬁciency arise as a result of pressure from the rib on the lowest

trunk of the brachial plexus (T1) and subclavian artery, respectively

(Fig. 1.3).

• The 2nd rib is less curved and longer than the 1st rib.

• The 10th rib has only one articular facet on the head.

• The 11th and 12th ribs are short and do not articulate anteriorly.

They articulate posteriorly with the vertebrae by way of a single facet

on the head. They are devoid of both a tubercle and a subcostal groove.

The sternum(Fig. 1.1)

The sternum comprises a manubrium, body and xiphoid process.

• The manubrium has facets for articulation with the clavicles, 1st

costal cartilage and upper part of the 2nd costal cartilage. It articulates

inferiorly with the body of the sternum at the manubriosternal joint.

• The body is composed of four parts or sternebrae which fuse between

15 and 25 years of age. It has facets for articulation with the lower part

of the 2nd and the 3rd to 7th costal cartilages.

• The xiphoid articulates above with the body at the xiphisternal joint.

The xiphoid usually remains cartilaginous well into adult life.

Costal cartilages

These are bars of hyaline cartilage which connect the upper seven ribs

directly to the sternum and the 8th, 9th and 10th ribs to the cartilage

immediately above.

Joints of the thoracic cage (Figs 1.1 and 1.4)

• The manubriosternal joint is a symphysis. It usually ossiﬁes after the

age of 30.

• The xiphisternal joint is also a symphysis.

• The 1st sternocostal joint is a primary cartilaginous joint. The rest

(2nd to 7th) are synovial joints. All have a single synovial joint except

for the 2nd which is double.

• The costochondral joints (between ribs and costal cartilages) are prim-

ary cartilaginous joints.

• The interchondral joints (between the costal cartilages of the 8th, 9th

and 10th ribs) are synovial joints.

• The costovertebral joints comprise two synovial joints formed by the

articulations of the demifacets on the head of each rib with the bodies of

its corresponding vertebra together with that of the vertebra above. The

1st and 10th–12th ribs have a single synovial joint with their corres-

ponding vertebral bodies.

• The costotransverse joints are synovial joints formed by the articula-

tions between the facets on the rib tubercle and the transverse process

of its corresponding vertebra.

The thoracic wall I 7

AAAC01 21/5/05 10:38 AM Page 7

8 Thorax

2 The thoracic wall II

Vein

Artery

Nerve

External

Internal Intercostal muscles

Intercostal

Innermost

Xiphisternum

Internal

thoracic artery

Lateral branch

lateral

Cutaneous

branches

Pleural and

peritoneal

sensory

branches

Intercostal

nerve

Posterior ramus

Posterior

intercostal

artery

intercostal

artery

Aorta

Spinal

branch

Costal margin

Central tendon

Inferior vena cava

Oesophagus

Aorta

Vertebral

levels

Lateral arcuate ligament

Medial arcuate ligament

Right crus

Psoas major

Quadratus lumborum

Third lumbar vertebra

Fig.2.1

An intercostal space

Fig.2.3

The diaphragm

Fig.2.2

The vessels and nerves

of an intercostal space

T10

T12

Collateral branch

(to muscles)

AAAC02 21/5/05 10:38 AM Page 8

The intercostal space (Fig. 2.1)

Typically, each space contains three muscles comparable to those of

the abdominal wall. These include the:

• External intercostal: this muscle ﬁlls the intercostal space from the

vertebra posteriorly to the costochondral junction anteriorly where it

becomes the thin anterior intercostal membrane. The ﬁbres run down-

wards and forwards from rib above to rib below.

• Internal intercostal: this muscle ﬁlls the intercostal space from the

sternum anteriorly to the angles of the ribs posteriorly where it becomes

the posterior intercostal membrane which reaches as far back as the

vertebral bodies. The ﬁbres run downwards and backwards.

• Innermost intercostals: this group comprises the subcostal muscles

posteriorly, the intercostales intimilaterally and the transversus thor-

acis anteriorly. The ﬁbres of these muscles span more than one inter-

costal space.

The neurovascular space is the plane in which the neurovascular

bundle (intercostal vein, artery and nerve) courses. It lies between the

internal intercostal and innermost intercostal muscle layers.

The intercostal structures course under cover of the subcostal

groove. Pleural aspiration should be performed close to the upper bor-

der of a rib to minimize the risk of injury.

Vascular supply and venous drainage of the chest wall

The intercostal spaces receive their arterial supply from the anterior

and posterior intercostal arteries.

• The anterior intercostal arteries are branches of the internal thoracic

artery and its terminal branch the musculophrenic artery. The lowest

two spaces have no anterior intercostal supply (Fig. 2.2).

• The ﬁrst 2–3 posterior intercostal arteries arise from the superior

intercostal branch of the costocervical trunk, a branch of the 2nd part of

the subclavian artery (see Fig. 60.1). The lower nine posterior inter-

costal arteries are branches of the thoracic aorta. The posterior inter-

costal arteries are much longer than the anterior intercostal arteries

(Fig. 2.2).

The anterior intercostal veins drain anteriorly into the internal thor-

acic and musculophrenic veins. The posterior intercostal veins drain

into the azygos and hemiazygos systems (see Fig. 4.2).

Lymphatic drainage of the chest wall

Lymph drainage from the:

• Anterior chest wall: is to the anterior axillary nodes.

• Posterior chest wall: is to the posterior axillary nodes.

• Anterior intercostal spaces: is to the internal thoracic nodes.

• Posterior intercostal spaces: is to the para-aortic nodes.

Nerve supply of the chest wall (Fig. 2.2)

The intercostal nerves are the anterior primary rami of the thoracic seg-

mental nerves. Only the upper six intercostal nerves run in their inter-

costal spaces, the remainder gaining access to the anterior abdominal

wall.

Branches of the intercostal nerves include:

• Cutaneous anterior and lateral branches.

•Acollateralbranch which supplies the muscles of the intercostal

space (also supplied by the main intercostal nerve).

• Sensory branches from the pleura (upper nerves) and peritoneum

(lower nerves).

Exceptions include:

• The 1st intercostal nerve is joined to the brachial plexus and has no

anterior cutaneous branch.

• The 2nd intercostal nerve is joined to the medial cutaneous nerve of

the arm by the intercostobrachial nerve branch. The 2nd intercostal

nerve consequently supplies the skin of the armpit and medial side of

the arm.

The diaphragm (Fig. 2.3)

The diaphragm separates the thoracic and abdominal cavities. It is com-

posed of a peripheral muscular portion which inserts into a central

aponeurosis

athe central tendon.

The muscular part has three component origins:

•A vertebral part: this comprises the crura and arcuate ligaments.

The right crus arises from the front of the L1–3 vertebral bodies and

intervening discs. Some ﬁbres from the right crus pass around the lower

oesophagus.

The left crus originates from L1 and L2 only.

The medial arcuate ligament is made up of thickened fascia which

overlies psoas major and is attached medially to the body of L1 and lat-

erally to the transverse process of L1. The lateral arcuate ligament is

made up of fascia which overlies quadratus lumborum from the trans-

verse process of L1 medially to the 12th rib laterally.

The median arcuate ligament is a ﬁbrous arch which connects left

and right crura.

•A costal part: attached to the inner aspects of the lower six ribs.

•A sternal part: consists of two small slips arising from the deep sur-

face of the xiphoid process.

Openings in the diaphragm

Structures traverse the diaphragm at different levels to pass from

thoracic to abdominal cavities and vice versa. These levels are as

follows:

• T8, theopening for the inferior vena cava: transmits the inferior vena

cava and right phrenic nerve.

• T10, the oesophageal opening: transmits the oesophagus, vagi and

branches of the left gastric artery and vein.

• T12, theaortic opening: transmits the aorta, thoracic duct and azygos

vein.

The left phrenic nerve passes into the diaphragm as a solitary

structure.

Nerve supply of the diaphragm

• Motor supply: the entire motor supply arises from the phrenic nerves

(C3,4,5). Diaphragmatic contraction is the mainstay of inspiration.

• Sensory supply: the periphery of the diaphragm receives sensory

ﬁbres from the lower intercostal nerves. The sensory supply from the

central part is carried by the phrenic nerves.

The thoracic wall II 9

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10 Thorax

The mediastinum Icthe contents of the mediastinum

Jugular lymph trunks

Thoracic duct

From lower limbs

Superior vena cava

From chest wall (right)

From chest wall (left)

Middle mediastinum

Heart and roots of great vessels

Pericardium

Superior mediastinum

Great vessels

Trachea

Oesophagus

Thymus, etc.

Anterior mediastinum

Thymus

Posterior mediastinum

Oesophagus

Descending thoracic aorta

Thoracic duct

Azygos and hemiazygos veins

Sympathetic trunk, etc.

Diaphragm

Cisterna chyli

From abdominal

viscera

Thoracic duct

Recurrent

laryngeal nerve

Oesophagus

Trachea

Left vagus

pulmonary

plexus

Oesophageal

plexus

vagal trunk

Oesophageal

opening (T10)

Aortic opening

(T12)

Left crus

Right

vagus

Azygos

vein

Diaphragm

Right

crus

Subclavian lymph trunk

Bronchomediastinal

lymph trunk

Right lymph duct

From kidneys and

abdominal wall

Fig.3.2

The course and principal relations of the oesophagus.

Note that it passes through the right crus of the

diaphragm

Fig.3.3

The thoracic duct and its areas of drainage.

The right lymph duct is also shown

Fig.3.1

The subdivisions of the mediastinum

and their principal contents

AAAC03 21/5/05 10:38 AM Page 10

Subdivisions of the mediastinum (Fig. 3.1)

The mediastinum is the space located between the two pleural sacs. For

descriptive purposes it is divided into superior and inferior mediastinal

regions by a line drawn backwards horizontally from the angle of Louis

(manubriosternal joint) to the vertebral column (T4/5 intervertebral disc).

The superior mediastinum communicates with the root of the neck

through the ‘thoracic inlet’. The latter opening is bounded anteriorly by

the manubrium, posteriorly by T1 vertebra and laterally by the 1st rib.

Theinferior mediastinum is further subdivided into the:

• Anterior mediastinum: the region in front of the pericardium.

• Middle mediastinum: consists of the pericardium and heart.

• Posterior mediastinum: the region between the pericardium and

vertebrae.

The contents of the mediastinum (Figs 3.1 and 3.2)

The oesophagus

• Course: the oesophagus commences as a cervical structure at the

level of the cricoid cartilage at C6 in the neck. In the thorax the oesoph-

agus passes initially through the superior and then the posterior medi-

astina. Having deviated slightly to the left in the neck the oesophagus

returns to the midline in the thorax at the level of T5. From here, it

passes downwards and forwards to reach the oesophageal opening in

the diaphragm (T10).

• Structure: the oesophagus is composed of four layers:

• An inner mucosa of stratiﬁed squamous epithelium.

• A submucous layer.

• A double muscular layer

alongitudinal outer layer and circular

inner layer. The muscle is striated in the upper two-thirds and

smooth in the lower third.

• An outer layer of areolar tissue.

• Relations: the relations of the oesophagus are shown in Fig. 3.2. On

the right side the oesophagus is crossed only by the azygos vein and the

right vagus nerve and hence this forms the least hazardous surgical

approach.

• Arterial supply and venous drainage: owing to the length of this

structure (25cm), the oesophagus receives arterial blood from varied

sources throughout its course:

• Upper third

ainferior thyroid artery.

• Middle third

aoesophageal branches of thoracic aorta.

• Lower third

aleft gastric branch of coeliac artery.

Similarly the venous drainage varies throughout its length:

• Upper third

ainferior thyroid veins.

• Middle third

aazygos system.

• Lower third

aboth the azygos (systemic system) and left gastric

veins (portal system).

The dual drainage of the lower third forms a site of portal-systemic

anastomosis. In advanced liver cirrhosis, portal pressure rises result-

ing in back-pressure on the left gastric tributaries at the lower oesoph-

agus. These veins become distended and fragile (oesophageal varices).

They are predisposed to rupture, causing potentially life-threatening

haemorrhage.

• Lymphatic drainage: this is to a peri-oesophageal lymph plexus and

then to the posterior mediastinal nodes. From here lymph drains into

supraclavicular nodes. The lower oesophagus also drains into the nodes

around the left gastric vessels.

Carcinoma of the oesophagus carries an extremely poor prognosis.

Two main histological types

bsquamous and adenocarcinomab

account for the majority of tumours. The incidence of adenocarcinoma of

the lower third of the oesophagus is currently increasing for unknown

reasons. Most tumours are unresectable at the time of diagnosis. The

insertion of stents and use oflasers to pass through tumour obstruction

have become the principal methods of palliation.

The thoracic duct (Fig. 3.3)

• The cisterna chyli is a lymphatic sac that receives lymph from the

abdomen and lower half of the body. It is situated between the abdom-

inal aorta and the right crus of the diaphragm.

• The thoracic duct carries lymph from the cisterna chyli through the

thorax to drain into the left brachiocephalic vein. It usually receives

tributaries from the left jugular, subclavian and mediastinal lymph

trunks, although they may open into the large neck veins directly.

• On the right side the main lymph trunks from the right upper body

usually join and drain directly through a common tributary, the right

lymph duct, into the right brachiocephalic vein.

The thymus gland

• This is an important component of the lymphatic system. It usually

lies behind the manubrium (in the superior mediastinum) but can

extend to about the 4th costal cartilage in the anterior mediastinum.

After puberty the thymus is gradually replaced by fat.

The mediastinum Ibthe contents of the mediastinum 11

AAAC03 21/5/05 10:38 AM Page 11

12 Thorax

The mediastinum IIcthe vessels of the thorax

Thyrocervical trunk

Suprascapular

Inferior thyroid

Superficial cervical

Scalenus anterior

Dorsal scapular

Subclavian

Anterior intercostals

Internal thoracic (mammary)

Musculophrenic

Superior epigastric

Inferior thyroid

Deep cervical

Left internal jugular

Thoracic duct

Vertebral

Left subclavian

Internal thoracic

Left superior intercostal

Vagus nerve

Phrenic nerve

Crossing arch

of the aorta

Posterior intercostal

Posterior intercostals

(also supply spinal cord)

Bronchial

Oesophageal

Mediastinal

Aortic opening in diaphragm

(T12)

branches

Right lymph duct

Left brachiocephalic

Costocervical trunk

Thyroidea ima

Superior intercostal

Upper two posterior

intercostals

Brachiocephalic

Inferior laryngeal

Right brachiocephalic

Superior vena cava

Right atrium

Azygos

Diaphragm

Accessory hemiazygos

Hemiazygos

Fig.4.2

The principal veins of the thorax

Fig.4.1

The branches of the arch and the descending thoracic aorta

Vertebral

Subcostal

AAAC04 21/5/05 10:37 AM Page 12

The thoracic aorta (Fig. 4.1)

The ascending aorta arises from the aortic vestibule behind the

infundibulum of the right ventricle and the pulmonary trunk. It is con-

tinuous with the aortic arch. The arch lies posterior to the lower half of

the manubrium and arches from front to back over the left main

bronchus. The descending thoracic aorta is continuous with the arch

and begins at the lower border of the body of T4. It initially lies slightly

to the left of the midline and then passes medially to gain access to the

abdomen by passing beneath the median arcuate ligament of the

diaphragm at the level of T12. From here it continues as the abdominal

aorta.

The branches of the ascending aorta are the:

• Right and left coronary arteries.

The branches of the aortic arch are the:

• Brachiocephalic artery: arises from the arch behind the manubrium

and courses upwards to bifurcate into right subclavian andright com-

mon carotid branches posterior to the right sternoclavicular joint.

• Left common carotid artery: see p. 133.

• Left subclavian artery.

• Thyroidea ima artery.

The branches of the descending thoracic aorta include the:

• Oesophageal, bronchial, mediastinal, posterior intercostal and sub-

costal arteries.

The subclavian arteries (see Fig. 60.1)

The subclavian arteries become the axillary arteries at the outer bor-

der of the 1st rib. Each artery is divided into three parts by scalenus

• 1st part: the part of the artery that lies medial to the medial border of

scalenus anterior. It gives rise to three branches, the: vertebral artery

(p. 135),thyrocervical trunk and internal thoracic (mammary) artery.

The latter artery courses on the posterior surface of the anterior chest

wall one ﬁngerbreadth from the lateral border of the sternum. Along

its course it gives off anterior intercostal, thymic and perforating

branches. The ‘perforators’ pass through the anterior chest wall to

supply the breast. The internal thoracic artery divides behind the 6th

costal cartilage into superior epigastric and musculophrenic branches.

The thyrocervical trunk terminates as the inferior thyroid artery.

• 2nd part: the part of the artery that lies behind scalenus anterior. It

gives rise to the costocervical trunk (see Fig. 60.1).

• 3rd part: the part of the artery that lies lateral to the lateral border of

scalenus anterior. This part gives rise to the dorsal scapular artery.

The great veins (Fig. 4.2)

The brachiocephalic veinsare formed by the conﬂuence of the subcla-

vian andinternal jugular veins behind the sternoclavicular joints. The

left brachiocephalic vein traverses diagonally behind the manubrium to

join the right brachiocephalic vein behind the 1st costal cartilage thus

forming thesuperior vena cava. The superior vena cava receives only

one tributary

athe azygos vein.

The azygos system of veins (Fig. 4.2)

• The azygos vein: commences as the union of the right subcostal vein

and one or more veins from the abdomen. It passes through the aortic

opening in the diaphragm, ascends on the posterior chest wall to the

level of T4 and then arches over the right lung root to enter the superior

vena cava. It receives tributaries from the: lower eight posterior inter-

costal veins, right superior intercostal vein and hemiazygos veins.

• The hemiazygos vein: arises on the left side in the same manner as the

azygos vein. It passes through the aortic opening in the diaphragm and

up to the level of T9 from where it passes diagonally behind the aorta

and thoracic duct to drain into the azygos vein at the level of T8. It

receives venous blood from the lower four left posterior intercostal

veins.

• The accessory hemiazygos vein: drains blood from the middle poster-

ior intercostal veins (as well as some bronchial and mid-oesophageal

veins). The accessory hemiazygos crosses to the right to drain into the

azygos vein at the level of T7.

• The upper four left intercostal veins drain into the left brachio-

cephalic vein via the left superior intercostal vein.

The mediastinum IIbthe vessels of the thorax 13

AAAC04 21/5/05 10:37 AM Page 13

14 Thorax

5 The pleura and airways

Apical

Right main bronchus

Left main bronchus

Posterior

Middle

Lingular

Anterior basal

Lateral basal

Posterior basal

Trachea

Anterior basal

Lateral basal

Apical of

lower lobe

Medial basal

Posterior basal

Posterior

Cricoid (C6)

Apico-posterior

Pulmonary artery

Bronchus

Pulmonary veins

Lymph node

Cut edge of pleura

Pulmonary ligament

Fig. 5.1

The principal structures

in the hilum of the lung

Fig. 5.2

The trachea and main bronchi

Brachiocephalic

artery

Superior

vena cava

Right

pulmonary

artery

Thyroid

isthmus

Left

brachiocephalic

vein

Aortic arch

Fig. 5.3

The anterior relations of the trachea

AAAC05 23/05/2005 2:59 PM Page 14

The respiratory tract is most often discussed in terms of upper and

lower parts. The upper respiratory tract relates to the nasopharynx and

larynx whereas the lower relates to the trachea, bronchi and lungs.

The pleurae

• Each pleura consists of two layers: a visceral layerwhich is adherent

to the lung and a parietal layerwhich lines the inner aspect of the chest

wall, diaphragm and sides of the pericardium and mediastinum.

• At the hilum of the lung the visceral and parietal layers become con-

tinuous. This cuff hangs loosely over the hilum and is known as the pul-

monary ligament. It permits expansion of the pulmonary veins and

movement of hilar structures during respiration (Fig. 5.1).

• The two pleural cavities do not connect.

• The pleural cavity contains a small amount of pleural ﬂuid which acts

as a lubricant decreasing friction between the pleurae.

• During maximal inspiration the lungs almost ﬁll the pleural cavities.

In quiet inspiration the lungs do not expand fully into the costo-

diaphragmatic and costomediastinal recesses of the pleural cavity.

• The parietal pleura is sensitive to pain and touch (carried by the inter-

costal and phrenic nerves). The visceral pleura is sensitive only to

stretch (carried by autonomic afferents from the pulmonary plexus).

Air can enter the pleural cavity following a fractured rib or a torn

lung (pneumothorax). This eliminates the normal negative pleural

pressure, causing the lung to collapse.

Inﬂammation of the pleura (pleurisy) results from infection of the

adjacent lung (pneumonia). When this occurs the inﬂammatory process

renders the pleura sticky. Under these circumstances a pleural rub can

often be auscultated over the affected region during inspiration and

expiration. Pus in the pleural cavity (secondary to an infective process)

is termed an empyema.

The trachea (Fig. 5.2)

• Course: the trachea commences at the level of the cricoid cartilage in

the neck (C6). It terminates at the level of the angle of Louis (T4/5)

where it bifurcates into right and left main bronchi.

• Structure: the trachea is a rigid ﬁbroelastic structure. Incom-

plete rings of hyaline cartilage continuously maintain the patency of

the lumen. The trachea is lined internally with ciliated columnar

epithelium.

• Relations: behind the trachea lies the oesophagus. The 2nd, 3rd and

4th tracheal rings are crossed anteriorly by the thyroid isthmus (Figs 5.3

and 64.1).

• Blood supply: the trachea receives its blood supply from branches of

the inferior thyroid and bronchial arteries.

The bronchi and bronchopulmonary segments (Fig. 5.2)

• The right main bronchus is shorter, wider and takes a more vertical

course than the left. The width and vertical course of the right main

bronchus account for the tendency for inhaled foreign bodies to prefer-

entially impact in the right middle and lower lobe bronchi.

• The left main bronchus enters the hilum and divides into a superior

and inferior lobar bronchus. The right main bronchus gives off the

bronchus to the upper lobe prior to entering the hilum and once into the

hilum divides into middle and inferior lobar bronchi.

• Each lobar bronchus divides within the lobe into segmental bronchi.

Each segmental bronchus enters a bronchopulmonary segment.

• Each bronchopulmonary segment is pyramidal in shape with its apex

directed towards the hilum (see Fig. 6.1). It is a structural unit of a lobe

that has its own segmental bronchus, artery and lymphatics. If one

bronchopulmonary segment is diseased it may be resected with pre-

servation of the rest of the lobe. The veins draining each segment are

intersegmental.

Bronchial carcinoma is the commonest cancer among men in the

United Kingdom. Four main histological types occur of which small

cell carries the worst prognosis. The overall prognosis remains

appalling with only 10% of sufferers surviving 5 years. It occurs most

commonly in the mucous membranes lining the major bronchi near the

hilum. Local invasion and spread to hilar and tracheobronchial nodes

occurs early.

The pleura and airways 15

AAAC05 23/05/2005 2:59 PM Page 15

16 Thorax

6 The lungs

4 and 5

Apical

Posterior (1 and 2 from a common apico-posterior stem on the left side)

Lateral and medial middle lobe (superior and inferior lingular on left side)

Superior (apical)

Medial basal (cardiac on left)

Anterior basal (7 and 8 often by a common stem on left)

Lateral basal

Posterior basal

Upper lobe

Middle lobe

Lower lobe

LEFT LUNG RIGHT LUNG

Fig. 6.1

The segmental bronchi (viewed from

the lateral side) and the broncho-

pulmonary segments, with their

standard numbering

Fig. 6.2

P–A. Chest X-ray

Trachea

Arch of aorta

Lung hilum

Left ventricle

Costophrenic angle

Breast shadow

Right atrium

Diaphragm

AAAC06 21/5/05 10:36 AM Page 16

The lungs (Fig. 6.1)

• The lungs provide an alveolar surface area of approximately 40 m

for gaseous exchange.

• Each lung has: an apex which reaches above the sternal end of the 1st

rib; a costovertebral surface which underlies the chest wall; a base

overlying the diaphragm and a mediastinalsurface which is moulded to

adjacent mediastinal structures.

• Structure: the right lung is divided into upper, middle and lower

lobes by oblique and horizontal ﬁssures. The left lung has only an

oblique ﬁssure and hence no middle lobe. The lingular segmentrepres-

ents the left sided equivalent of the right middle lobe. It is, however, an

anatomical part of the left upper lobe.

Structures enter or leave the lungs by way of the lung hilum which,

as mentioned earlier, is ensheathed in a loose pleural cuff (see Fig. 5.1).

• Blood supply: the bronchi and parenchymal tissue of the lungs are

supplied by bronchial arteries

abranches of the descending thoracic

aorta. Bronchial veins, which also communicate with pulmonary veins,

drain into the azygos and hemiazygos. The alveoli receive deoxy-

genated blood from terminal branches of the pulmonary artery and oxy-

genated blood returns via tributaries of the pulmonary veins. Two

pulmonary veins return blood from each lung to the left atrium.

• Lymphatic drainage of the lungs: lymph returns from the periphery

towards the hilar tracheobronchial groups of nodes and from here to

mediastinal lymph trunks.

• Nerve supply of the lungs: a pulmonary plexus is located at the root

of each lung. The plexus is composed of sympathetic ﬁbres (from the

sympathetic trunk) and parasympathetic ﬁbres (from the vagus).

Efferent ﬁbres from the plexus supply the bronchial musculature and

afferents are received from the mucous membranes of bronchioles and

from the alveoli.

The mechanics of respiration

• A negative intrapleural pressure keeps the lungs continuously par-

tially inﬂated.

• During normal inspiration: contraction of the upper external inter-

costals increases the A-P diameter of the upper thorax; contraction of

the lower external intercostals increases the transverse diameter of the

lower thorax; and contraction of the diaphragm increases the vertical

length of the internal thorax. These changes serve to increase lung vol-

ume and thereby result in reduction of intrapulmonary pressure causing

air to be sucked into the lungs. In deep inspiration the sternocleidomas-

toid, scalenus anterior and medius, serratus anterior and pectoralis

major and minor all aid to maximize thoracic capacity. The latter are

termed collectively

athe accessory muscles of respiration.

• Expiration is mostly due to passive relaxation of the muscles of inspira-

tion and elastic recoil of the lungs. In forced expiration the abdominal

musculature aids ascent of the diaphragm.

The chest X-ray (CXR) (Fig. 6.2)

The standard CXR is the postero-anterior (PA) view. This is taken with

the subject’s chest touching the cassette holder and the X-ray beam

directed anteriorly from behind.

Structures visible on the chest X-ray include the:

• Heart borders: any signiﬁcant enlargement of a particular chamber

can be seen on the X-ray. In congestive cardiac failure all four cham-

bers of the heart are enlarged (cardiomegaly). This is identiﬁed on the

PA view as a cardiothoracic ratio greater than 0.5. This ratio is calcu-

lated by dividing the width of the heart by the width of the thoracic cav-

ity at its widest point.

• Lungs: the lungs are radiolucent. Dense streaky shadows, seen at the

lung roots, represent the blood-ﬁlled pulmonary vasculature.

• Diaphragm: the angle made between the diaphragm and chest wall is

termed the costophrenic angle. This angle is lost when a pleural effu-

sion collects.

• Mediastinal structures: these are difﬁcult to distinguish as there is

considerable overlap. Clearly visible, however, is the aortic arch

which, when pathologically dilated (aneurysmal), creates the impres-

sion of ‘widening’ of the mediastinum.

The lungs 17

AAAC06 21/5/05 10:36 AM Page 17

18 Thorax

7 The heart I

Right vagus

Right phrenic

Brachiocephalic artery

Right

brachiocephalic vein

Right pulmonary veins

Right atrium

Inferior vena cava

Superior vena cava

Inferior thyroid veins

Left subclavian artery

Left common carotid artery

Left vagus

Left phrenic

Left brachiocephalic vein

Left pulmonary artery

Left recurrent laryngeal

Left bronchus

Left pulmonary veins

Thyroid

Pulmonary veins

Pericardium Heart

Back of left atrium

Back of right atrium

Inferior vena cava

Parietal pericardium

Visceral pericardium

Arrow in transverse sinus

Pulmonary trunk

Arrow in oblique sinus

Aorta

Right recurrent laryngeal

Fig.7.1

The heart and the great vessels

Fig.7.2

The sinuses of the pericardium. The heart has been removed from the pericardial cavity and turned over to show its

posterior aspect. The red line shows the cut edges where the visceral pericardium is continuous with the parietal pericardium.

Visceral layer: blue, parietal layer: red

AAAC07 21/5/05 10:36 AM Page 18

The heart I 19

• Blood supply: from the pericardiacophrenic branches of the internal

thoracic arteries.

• Nerve supply: the ﬁbrous pericardium and the parietal layer of

serous pericardium are supplied by the phrenic nerve.

Following thoracic trauma blood can collect in the pericardial

space (haemopericardium) which may, in turn, lead to cardiac tam-

ponade. This manifests itself clinically as shock, distended neck veins

and mufﬂed/absent heart sounds (Beck’s triad). This condition is fatal

unless pericardial decompression is effected immediately.

The heart surfaces

•Theanterior (sternocostal) surface comprises the: right atrium, atri-

oventricular groove, right ventricle, a small strip of left ventricle and

the auricle of the left atrium.

•Theinferior (diaphragmatic) surface comprises the: right atrium,

atrioventricular groove and both ventricles separated by the interven-

tricular groove.

•Theposteriorsurface (base) comprises the left atrium receiving the

four pulmonary veins.

The heart, pericardium, lung roots and adjoining parts of the great ves-

sels constitute the middle mediastinum (Figs 3.1 and 7.1).

The pericardium

The pericardium comprises ﬁbrous and serous components. The

ﬁbrous pericardium is a strong layer which covers the heart. It fuses

with the roots of the great vessels above and with the central tendon of

the diaphragm below. The serous pericardium lines the ﬁbrous peri-

cardium (parietal layer) and is reﬂected at the vessel roots to cover the

heart surface (visceral layer). The serous pericardium provides smooth

surfaces for the heart to move against. Two important sinuses are

located between the parietal and visceral layers. These are the:

• Transverse sinus

alocated between the superior vena cava and left

atrium posteriorly and the pulmonary trunk and aorta anteriorly

(Fig. 7.2).

• Oblique sinus

abehind the left atrium, the sinus is bounded by the

inferior vena cava and the pulmonary veins (Fig. 7.2).

AAAC07 21/5/05 10:36 AM Page 19

20 Thorax

Portion of right

atrium derived

from sinus

venosus

Crista

terminalis

Inferior

vena cava

Fossa ovalis

Opening of

coronary sinus

Valve of the

coronary sinus

Valve of the inferior

vena cava

Musculi

pectinati

Superior vena cava

Limbus

fossa ovalis

Pulmonary valve

(posterior, anterolateral

and anteromedial cusps)

Mitral

valve

Opening of right coronary artery

Aortic valve

(Anterior (right coronary) cusp,

Left posterior (left coronary) cusp,

right posterior (non-coronary) cusp)

Right atrium

Left atrium

Tricuspid valve

Posterior

cusp

Posterior

cusp

Septal

cusp

Fig.7.3

The interior of the right atrium

Fig.7.4

The interior of the left atrium and ventricle.

The arrow shows the direction of blood flow.

Note that blood flows over both surfaces

of the anterior cusp of the mitral valve

Fig.7.5

A section through the heart at the level of the valves.

The aortic and pulmonary valves are closed and the

mitral and tricuspid valves open, as they would be

during ventricular diastole

AAAC07 21/5/05 10:36 AM Page 20

The heart chambers

The right atrium (Fig. 7.3)

• Receives deoxygenated blood from the inferior vena cava below and

from the superior vena cava above.

• Receives the coronary sinusin its lower part (p. 23).

• The upper end of the atrium projects to the left of the superior vena

cava as the right auricle.

• The sulcus terminalis is a vertical groove on the outer surface of the

atrium. This groove corresponds internally to the crista terminalis

muscular ridge which separates the smooth walled atrium (derived

from the sinus venosus) from the rest of the atrium (derived from the

true fetal atrium). The latter contains horizontal ridges of muscle

musculi pectinati.

• Above the coronary sinus the interatrial septum forms the posterior

wall. The depression in the septum

athe fossa ovalisarepresents the

site of the foramen ovale. Its ﬂoor is the fetal septum primum. The

upper ridge of the fossa ovalis is termed the limbus, which represents

the septum secundum. Failure of fusion of the septum primum with the

septum secundum gives rise to a patent foramen ovale (atrial septal

defect) but as long as the two septa still overlap, there will be no func-

tional disability. A patent foramen gives rise to a left–right shunt.

The right ventricle

• Receives blood from the right atrium through the tricuspid valve (see

below). The edges of the valve cusps are attached to chordae tendineae

which are, in turn, attached below to papillary muscles. The latter are

projections of muscle bundles on the ventricular wall.

• The wall of the right ventricle is thicker than that of the atria but not

as thick as that of the left ventricle. The wall contains a mass of muscu-

lar bundles known as trabeculae carneae. One prominent bundle pro-

jects forwards from the interventricular septum to the anterior wall.

This is the moderator band (or septomarginal trabecula) and is of

importance in the conduction of impulses as it contains the right branch

of the atrioventricular bundle.

• The infundibulum is the smooth walled outﬂow tract of the right

ventricle.

• The pulmonary valve (see below) is situated at the top of the

infundibulum. It is composed of three semilunar cusps. Blood ﬂows

through the valve and into the pulmonary arteries via the pulmonary

trunk to be oxygenated in the lungs.

The left atrium

• Receives oxygenated blood from four pulmonary veins which drain

posteriorly.

• The cavity is smooth walled except for the atrial appendage.

• On the septal surface a depression marks the fossa ovalis.

• The mitral (bicuspid) valve guards the passage of blood from the left

atrium to the left ventricle.

The left ventricle (Fig. 7.4)

• The wall of the left ventricle is considerably thicker than that of the

right ventricle but the structure is similar. The thick wall is necessary to

pump oxygenated blood at high pressure through the systemic circula-

tion. Trabeculae carneae project from the wall with papillary muscles

attached to the mitral valve cusp edges by way of chordae tendineae.

• The vestibule is a smooth walled part of the left ventricle which is

located below the aortic valve and constitutes the outﬂow tract.

The heart valves (Fig. 7.5)

• The purpose of valves within the heart is to maintain unidirectional ﬂow.

• The mitral (bicuspid) and tricuspid valves are ﬂat. During ventricular

systole the free edges of the cusps come into contact and eversion is

prevented by the pull of the chordae. Papillary muscle rupture can

occur as a complication of myocardial infarction. This is evident clin-

ically by a pansystolic murmur representing regurgitant ﬂow of blood

from ventricle to atrium.

• The aortic and pulmonary valves are composed of three semilunar

cusps which are cup shaped. During ventricular diastole back-pressure

of blood above the cusps forces them to ﬁll and hence close.

The heart I 21

AAAC07 21/5/05 10:36 AM Page 21

22 Thorax

8 The heart II

Left coronary

artery

Posterior

interventricular

branch

Marginal

artery

Right coronary

artery

interventricular

branch

S–A node

Atrial conduction

Ventricular conduction

A–V node

Coronary

sinus

Small

cardiac

vein

Middle

cardiac

vein

Great

cardiac

vein

QRS

Fig.8.1

The coronary arteries.

Variations are common

Fig.8.3

The direction and timing of the spread

of action potential in the conducting

system of the heart.

Times are in msec

Fig.8.2

The venous drainage of the heart

Fig.8.4

An electrocardiogram

AAAC08 23/05/2005 3:06 PM Page 22

The grooves between the four heart chambers represent the sites that

offer the least stretch during systole and, for this reason, are where most

of the vessels supplying the heart are situated.

The arterial supply of the heart (Fig. 8.1)

The coronary arteries are responsible for supplying the heart itself with

oxygenated blood.

The coronary arteries are functional end-arteries and hence follow-

ing a total occlusion, the myocardium supplied by the blocked artery is

deprived of its blood supply (myocardial infarction). When the vessel

lumen gradually narrows due to atheromatous change of the walls,

patients complain of gradually increasing chest pain on exertion

(angina). Under these conditions the increased demand placed on the

myocardium cannot be met by the diminished arterial supply. Angina

that is not amenable to pharmacological control can be relieved by

dilating (angioplasty), or surgically bypassing (coronary artery bypass

grafting), the arterial stenosis. The latter procedure is usually per-

formed using a reversed length of great saphenous vein anastomosed to

the proximal aorta and then distally to the coronary artery beyond the

stenosis. Ischaemic heart disease is the leading cause of death in the

western world and consequently a thorough knowledge of the coronary

anatomy is essential.

The origins of the coronary arteries are as follows:

• The left coronary artery arises from the aortic sinus immediately

above the left posterior cusp of the aortic valve (see Fig. 7.5).

• The right coronary artery arises from the aortic sinus immediately

above the anterior cusp of the aortic valve (see Fig. 7.5).

There is considerable variation in size and distribution zones of the

coronary arteries. For example, in some people the posterior interven-

tricularbranch of the right coronary artery is large and supplies a large

part of the left ventricle whereas in the majority this is supplied by the

anterior interventricularbranch of the left coronary.

Similarly, the sinu-atrial nodeis usually supplied by a nodal branch

of the right coronary artery but in 30–40% of the population it receives

its supply from the left coronary.

The venous drainage of the heart (Fig. 8.2)

The venous drainage systems in the heart include:

• The veins which accompany the coronary arteries and drain into the

right atrium via the coronary sinus. The coronary sinus drains into the

right atrium to the left of and superior to the opening of the inferior vena

cava. The great cardiac vein follows the anterior interventricular

branch of the left coronary and then sweeps backwards to the left in the

atrioventricular groove. The middle cardiac veinfollows the posterior

interventricular artery and, along with the small cardiac veinwhich fol-

lows the marginal artery, drains into the coronary sinus. The coronary

sinus drains the vast majority of the heart’s venous blood.

• The venae cordis minimi: these are small veins which drain directly

into the cardiac chambers.

• The anterior cardiac veins: these are small veins which cross the atri-

oventricular groove to drain directly into the right atrium.

The conducting system of the heart (Figs 8.3 and 8.4)

• The sinu-atrial (SA) node is the pacemaker of the heart. It is situated

near the top of the crista terminalis, below the superior vena caval

opening into the right atrium. Impulses generated by the SA node are

conducted throughout the atrial musculature to effect synchronous

atrial contraction. Disease or degeneration of any part of the conduc-

tion pathway can lead to dangerous interruption of heart rhythm.

Degeneration of the SA node leads to other sites of the conduction path-

way taking over the pacemaking role, albeit usually at a slower rate.

• Impulses reach the atrioventricular (AV) node which lies in the

interatrial septum just above the opening for the coronary sinus. From

here the impulse is transmitted to the ventricles via the atrioventricular

bundle(of His) which descends in the interventricular septum.

• The bundle of His divides into right and left branches which send

Purkinje ﬁbresto lie within the subendocardium of the ventricles. The

position of the Purkinje ﬁbres accounts for the almost synchronous

contraction of the ventricles.

The nerve supply of the heart

The heart receives both a sympathetic and a parasympathetic nerve

supply so that heart rate can be controlled to demand.

• The parasympathetic supply (bradycardic effect): is derived from the

vagus nerve (p. 25).

• The sympathetic supply (tachycardic and positively inotropic effect):

is derived from the cervical and upper thoracic sympathetic ganglia by

way of superﬁcial and deep cardiac plexuses (p. 25).

The heart II 23

AAAC08 23/05/2005 3:06 PM Page 23

24 Thorax

9 The nerves of the thorax

Subclavian artery

Superior intercostal vein

Arch of aorta

Left recurrent laryngeal nerve

Left pulmonary artery

Posterior pulmonary plexus

Descending aorta

Oesophageal

plexus on oesophagus

Sympathetic trunk

Greater splanchnic nerve

Thoracic duct on side of oesophagus

Central tendon

of diaphragm

Inferior vena cava

Branches to fibrous

and parietal pericardium

Mediastinal pleura

Scalenus anterior

Fig.9.2

The structures on the left

side of the mediastinum.

They are all covered with

the mediastinal pleura

Fig.9.1

The course and distribution

of the right phrenic nerve

Fig.9.3

The structures on the right

side of the mediastinum

Subclavian artery

Subclavian vein

Left brachiocephalic

vein

Superior vena cava

Acending aorta

Bronchus

Pulmonary veins

Hilum of lung

Phrenic nerve

Oesophagus

Trachea

Vagus nerve

Intercostal vessels

and nerves

Posterior

pulmonary plexus

Greater

splanchnic nerve

Oesophageal plexus

on oesophagus

Right atrium

Pulmonary artery

Subclavian vein

Sensory to

diaphragmatic pleura

Sensory to

diaphragmatic peritoneum

Motor to diaphragm

Left common

carotid artery

Subclavian vein

Vagus nerve

Ligamentum

arteriosum

Pulmonary trunk

Left auricle

Phrenic nerve

Left ventricle

AAAC09 21/5/05 10:35 AM Page 24

The phrenic nerves

The phrenic nerves arise from the C3, C4 and C5 nerve roots in the

neck.

• The right phrenic nerve (Fig. 9.1) descends along a near vertical

path, anterior to the lung root, lying on sequentially: the right brachio-

cephalic vein, the superior vena cava, and the right atrium before pass-

ing to the inferior vena caval opening in the diaphragm (T8). Here the

right phrenic enters the caval opening and immediately penetrates the

diaphragm which it supplies.

• The left phrenic nerve (Fig. 9.2) descends alongside the left subcla-

vian artery. On the arch of the aorta it passes over the left superior inter-

costal vein to descend in front of the left lung root onto the pericardium

overlying the left ventricle. The left phrenic then pierces the muscular

diaphragm as a solitary structure. Note: the phrenic nerves do not pass

beyond the undersurface of the diaphragm.

• The phrenic nerves are composed mostly of motor ﬁbres which supply

the diaphragm. However, they also transmit ﬁbres which are sensory

to the ﬁbrous pericardium, mediastinal pleura and peritoneum as well

as the central part of the diaphragm.

Irritation of the diaphragmatic peritoneum is usually referred to the

C4 dermatome. Hence, upper abdominal pathology such as a perfor-

ated duodenal ulcer often results in pain felt at the shoulder tip.

The vagi

The vagi are the 10th cranial nerves (p. 145).

• The right vagus nerve (Figs 9.3 and 3.2) descends adherent to the thor-

acic trachea prior to passing behind the lung root to form the posterior

pulmonary plexus. It ﬁnally reaches the lower oesophagus where it

forms an oesophageal plexus with the left vagus. From this plexus,

anterior and posterior vagal trunks descend (carrying ﬁbres from both

left and right vagi) on the oesophagus to pass into the abdomen through

the oesophageal opening in the diaphragm at the level of T10.

• The left vagus nerve (Fig. 9.2) crosses the arch of the aorta and

its branches. It is itself crossed here by the left superior intercostal

vein. Below, it descends behind the lung root to reach the oesophagus

where it contributes to the oesophageal plexus mentioned above (see

Fig. 3.2).

Vagal branches

• The left recurrent laryngeal nerve arises from the left vagus below

the arch of the aorta. It hooks around the ligamentum arteriosum and

ascends in the groove between the trachea and the oesophagus to reach

the larynx (p. 139).

• The right recurrent laryngeal nerve arises from the right vagus in the

neck and hooks around the right subclavian artery prior to ascending in

the groove between the trachea and the oesophagus before ﬁnally

reaching the larynx.

• The recurrent laryngeal nerves supply the mucosa of the upper tra-

chea and oesophagus as well as providing a motor supply to all of the

muscles of the larynx (except cricothyroid) and sensory ﬁbres to the

lower larynx.

• The vagi also contribute branches to the cardiac and pulmonary

plexuses.

The thoracic sympathetic trunk (Figs 9.2 and 9.3, and

Chapter 53)

• The thoracic sympathetic chain is a continuation of the cervical

chain. It descends in the thorax behind the pleura immediately lateral to

the vertebral bodies and passes under the medial arcuate ligament of the

diaphragm to continue as the lumbar sympathetic trunk.

• The thoracic chain bears a ganglion for each spinal nerve; the ﬁrst

frequently joins the inferior cervical ganglion to form the stellate gan-

glion. Each ganglion receives a white ramus communicans containing

preganglionic ﬁbres from its corresponding spinal nerve and sends

back a grey ramus, bearing postganglionic ﬁbres.

Upper limb sympathectomy is used for the treatment of hyperhidro-

sis and Raynaud syndrome. Surgical sympathectomy involves excision

of part of the thoracic sympathetic chain (usually for two interspaces)

below the level of the stellate ganglion. The latter structure must be

identiﬁed on the neck of the 1st rib.

Branches:

• Sympathetic ﬁbres are distributed to the skin with each of the thor-

acic spinal nerves.

• Postganglionic ﬁbres from T1–5 are distributed to the thoracic

viscera

athe heart and great vessels, the lungs and the oesophagus.

• Mainly preganglionic ﬁbres from T5–12 form the splanchnic nerves,

which pierce the crura of the diaphragm and pass to the coeliac and

renal ganglia from which they are relayed as postganglionic ﬁbres to

the abdominal viscera (cf. ﬁbres to the suprarenal medulla which are

preganglionic). These splanchnic nerves are the: greater splanchnic

(T5–10), lesser splanchnic (T10–11) and lowest splanchnic (T12).

They lie medial to the sympathetic trunk on the bodies of the thoracic

vertebrae and are quite easily visible through the parietal pleura.

The cardiac plexus

This plexus is for descriptive purposes divided into superﬁcial and deep

parts. It consists of sympathetic and parasympathetic efferents as well

as afferents.

• Cardiac branches from the plexus supply the heart where they:

accompany coronary arteries for vasomotor control and supply the

sinu-atrial and atrioventricular nodes for cardio-inhibitory and cardio-

acceleratory purposes.

• Pulmonary branches supply the bronchial wall smooth muscle (con-

trolling diameter) and pulmonary blood vessels for vasomotor control.

The nerves of the thorax 25

AAAC09 21/5/05 10:35 AM Page 25

26 Thorax

10 Surface anatomy of the thorax

10 10

12 12

Cervical plexus

Cardiac notch of lung

Transverse fissure

Oblique fissure

Costodiaphragmatic recess

Apex of lower lung

Oblique fissure

Beginning of transverse fissure

Costodiaphragmatic recess

Mid-clavicular line

Fig.10.1

The surface markings of the

lungs and pleural cavities

Fig.10.2

The surface markings of the heart.

The areas of auscultation for the

aortic, pulmonary, mitral and

tricuspid valves are indicated by letters

AAAC10 21/5/05 10:35 AM Page 26

The anterior thorax

Landmarks of the anterior thorax include:

• The angle of Louis (sternal angle): formed by the joint between the

manubrium and body of the sternum. It is an important landmark as the

2nd costal cartilages articulate on either side and by following this line

onto the 2nd rib, further ribs and intercostal spaces can be identiﬁed.

The sternal angle corresponds to a horizontal point level with the inter-

vertebral disc between T4 and T5.

• The suprasternal notch: situated in the midline between the medial

ends of the clavicles and above the upper edge of the manubrium.

• The costal margin: formed by the lower borders of the cartilages of

the 7th, 8th, 9th and 10th ribs and the ends of the 11th and 12th ribs.

• The xiphisternal joint: formed by the joint between the body of the

sternum and xiphisternum.

The posterior thorax

Landmarks of the posterior thorax include:

• The ﬁrst palpable spinous process is that of C7 (vertebra prominens).

C1–6 vertebrae are covered by the thick ligamentum nuchae. The

spinous processes of the thoracic vertebrae can be palpated and counted

in the midline posteriorly.

• The scapula is located on the upper posterior chest wall. In slim sub-

jects the superior angle, inferior angle, spine and medial (vertebral)

border of the scapula are easily palpable.

Lines of orientation

These are imaginary vertical lines used to describe locations on the

chest wall. These include:

• The mid-clavicular line: a vertical line from the midpoint of the clav-

icle downwards.

• The anterior and posterior axillary lines: from the anterior and poster-

ior axillary folds, respectively, vertically downwards.

•Themid-axillary line: from the midpoint between anterior and poster-

ior axillary lines vertically downwards.

Vertebral levels

Palpable bony prominences can be used to identify the location of

important underlying structures. The following bony landmarks and

their corresponding vertebral levels are given:

• Suprasternal notch: T2/3.

• Sternal angle (angle of Louis): T4/5.

• Superior angle of the scapula: T2.

• Inferior angle of the scapula: T8.

• Xiphisternal joint: T9.

• Subcostal plane (lowest part of the costal margin): L3.

The surface markings of thoracic structures

The trachea

The trachea commences at the lower border of the cricoid cartilage (C6

vertebral level). It runs downwards in the midline and ends slightly to

the right by bifurcating into the left and right main bronchi. The bifurca-

tion occurs at the level of the sternal angle (T4/5).

The pleura (Fig. 10.1)

The apex of the pleura projects about 2.5cm above the medial third of

the clavicle. The lines of pleural reﬂection pass behind the sternoclavicu-

lar joints to meet in the midline at the level of the sternal angle. The

right pleura then passes downwards to the 6th costal cartilage. The left

pleura passes laterally for a small distance at the 4th costal cartilage and

descends vertically lateral to the sternal border to the 6th costal cartil-

age. From these points both pleurae pass posteriorly and in so doing

cross the 8th rib in the mid-clavicular line, the 10th rib in the mid-

axillary line and ﬁnally reach the level of the 12th rib posteriorly.

The lungs(Fig. 10.1)

The apex and mediastinal border of the right lung follow the pleural

outline. In mid-inspiration the right lung lower border crosses the 6th

rib in the mid-clavicular line, the 8th rib in the mid-axillary line and

reaches the level of the 10th rib posteriorly. The left lung borders are

similar to those of the right except that the mediastinal border arches

laterally (the cardiac notch) but then resumes the course mentioned

above.

• The oblique ﬁssure: is represented by an oblique line drawn from a

point 2.5cm lateral to the 5th thoracic spinous process to the 6th costal

cartilage anteriorly. The oblique ﬁssures separate the lungs into upper

and lower lobes.

• The transverse ﬁssure: is represented by a line drawn horizontally

from the 4th costal cartilage to a point where it intersects the oblique

ﬁssure. The ﬁssure separates the upper and middle lobes of the right

lung.

The heart

• The borders of the heart are illustrated by joining the four points

shown (Fig. 10.2).

• The apex of the left ventricle corresponds to where the apex beat is

palpable. The surface marking for the apex beat is in the 5th intercostal

space in the mid-clavicular line.

• See Fig. 10.2 for optimal sites of valvular auscultation.

The great vessels

• The aortic arch: arches antero-posteriorly behind the manubrium.

The highest point of the arch reaches the midpoint of the manubrium.

• The brachiocephalic artery and left common carotid artery: ascend

posterior to the manubrium.

• The brachiocephalic veins: are formed by the conﬂuence of the inter-

nal jugular and subclavian veins. This occurs posterior to the sterno-

clavicular joints.

• The superior vena cava: is formed by the conﬂuence of the left and

right brachiocephalic veins between the 2nd and 3rd right costal cartil-

ages at the right border of the sternum.

The breast

The base of the breast (p. 69) is constant, overlying the 2nd to the 6th

ribs and costal cartilages anteriorly and from the lateral border of the

sternum to the mid-axillary line. The position of the nipple is variable

in the female but in the man it is usually in the 4th intercostal space in

the mid-clavicular line.

The internal thoracic vessels

These arteries and veins descend 1cm lateral to the edge of the

sternum.

The diaphragm

In mid-inspiration the highest part of the right dome reaches as far as

the upper border of the 5th rib in the mid-clavicular line. The left dome

reaches only the lower border of the 5th rib.

Surface anatomy of the thorax 27

AAAC10 21/5/05 10:35 AM Page 27

28 Abdomen and pelvis

11 The abdominal wall

Linea

semilunaris

Serratus

Superficial

inguinal ring

Cut edge of external oblique

Fig.11.1

Two muscles of the anterior

abdominal wall.

The external oblique (on the right) and

the internal oblique (on the left)

Fig.11.2

The fibrous layer of superficial fascia

can be likened to a pair of bathing trunks

sewn to the thigh below the inguinal

ligament and clinging to the penis and

scrotum (except for the glans)

Fig.11.3

Transverse sections through

the rectus sheath.

A: above the costal margin

B: above the umbilicus

C: above the pubic symphysis

Linea alba

Cut edge of external oblique

Internal oblique

Anterior superior iliac spine

Inguinal ligament

Inguinal

ligament

Conjoint tendon

Pubic tubercle

Rectus abdominis

Dartos

muscle

Rectus abdominis

External oblique

Linea alba

Costal cartilages

External oblique

Internal oblique

Transversus abdominis

Transversalis fascia

Superior

epigastric

artery

Deep layer of

superficial fascia

Fascia penis

Colles' fascia

External oblique

Internal oblique

Transversus abdominis

Peritoneum

Inferior

epigastric

artery

AAAC11 21/5/05 10:43 AM Page 28

The abdominal wall 29

Fig.11.4

The inguinal canal.

(a) The superficial inguinal ring. The external

spermatic fascia has been removed

(b) After removal of the external oblique

Fig.11.6

The nerves and vessels of the abdominal wall

Fig.11.5

A schematic cross section through the spermatic cord

Superficial ring

Femoral artery

and vein in

femoral sheath

External oblique

aponeurosis

Transversus

Transversalis fascia

Position of deep ring

Position of

superficial ring

Ilioinguinal nerve

Spermatic cord

Femoral canal

Femoral artery

and vein in

femoral sheath

Internal oblique

(b)

(a)

Testicular artery and

pampiniform plexus of

veins

Lymphatics

Internal thoracic

Musculophrenic

Vas deferens

External spermatic

fascia

Cremasteric fascia and

muscle (striated)

Internal spermatic

fascia

Superior epigastric

Para-umbilical veins

anastomose with

epigastric veins

Lumbar

T10

T12

Ilioinguinal

Anterior cutaneous

branches of

intercostal nerves

Iliohypogastric

(lateral branch)

Iliohypogastric

(anterior cutaneous)

AAAC11 21/5/05 10:43 AM Page 29

deep circumﬂex iliac artery (a branch of the external iliac artery) an-

teriorly. The two lower intercostaland four lumbar arteries supply the

wall posterolaterally.

Veins of the abdominal wall (Fig. 11.6)

The abdominal wall is a site of porto-systemic anastomosis. The lateral

thoracic, lumbar and superﬁcial epigastric tributaries of the systemic

circulation anastomose around the umbilicus with the para-umbilical

veins which accompany the ligamentum teres and drain into the portal

circulation.

Lymph drainage of the abdominal wall

See p. 35.

The inguinal canal (Fig. 11.4)

The canal is approximately 4cm long and allows the passage of the

spermatic cord (round ligament in the female) through the lower ab-

dominal wall. The canal passes obliquely from the deep inguinal ring

in a medial direction to the superﬁcial inguinal ring.

• The deep ring: is an opening in the transversalis fascia. It lies half-

way between the anterior superior iliac spine and the pubic tubercle.

The inferior epigastric vessels pass medial to the deep ring.

• The superﬁcial ring: is not a ring but a triangular-shaped defect in

the external oblique aponeurosis lying above and medial to the pubic

tubercle.

The walls of the inguinal canal (Fig. 11.4)

• Anterior: external oblique covers the length of the canal anteriorly.

It is reinforced in its lateral third by internal oblique.

• Superior: internal oblique arches posteriorly to form the roof of the

canal.

• Posterior: transversalis fascia forms the lateral part of the posterior

wall. The conjoint tendon (the combined common insertion of the inter-

nal oblique and transversus into the pectineal line) forms the medial

part of the posterior wall.

• Inferior: the inguinal ligament.

Contents of the inguinal canal

• The spermatic cord (or round ligament in the female).

• The ilioinguinal nerve (L1).

The spermatic cord (Fig. 11.5)

The spermatic cord is covered by three layers which arise from the

layers of the lower abdominal wall as the cord passes through the

inguinal canal. These are the:

• External spermatic fascia: from the external oblique aponeurosis.

• Cremasteric fascia and muscle: from the internal oblique

aponeurosis.

• Internal spermatic fascia: from the transversalis fascia.

The contents of the spermatic cord include the:

• Ductus (vas) deferens (or round ligament).

• Testicular artery: a branch of the abdominal aorta.

• Pampiniform plexus of veins: these coalesce to form the testicular

vein in the region of the deep ring.

• Lymphatics: from the testis and epididymis draining to the pre-

aortic nodes.

• Autonomic nerves.

30 Abdomen and pelvis

The anterior abdominal wall comprises: skin, superﬁcial fascia, abdom-

inal muscles (and their respective aponeuroses), transversalis fascia,

extraperitoneal fat, and parietal peritoneum.

Skin (Fig. 11.6)

The skin of the abdominal wall is innervated by the anterior rami of the

lower six thoracic intercostal and iliohypogastric (L1) nerves.

Fascia (Fig. 11.2)

There is no deep fascia in the trunk. The superﬁcial fascia is composed

of two layers:

• A superﬁcial fatty layer

aCamper’s fasciaawhich is continuous with

the superﬁcial fat over the rest of the body.

• A deep ﬁbrous (membranous) layer

aScarpa’s fasciaawhich fades

above and laterally but below blends with the fascia lata of the thigh

just below the inguinal ligament and extends into: the penis as a tubular

sheath; the wall of the scrotum and posteriorly; the perineum where it

fuses with the perineal body and posterior margin of the perineal mem-

brane. It fuses laterally with the pubic arch. The ﬁbrous fascial layer is

referred to as Colles’ fasciain the perineum.

Muscles of the anterior abdominal wall (Fig. 11.1)

These comprise: external oblique,internal oblique, transversus abdo-

minis,rectus abdominis and pyramidalis (see Muscle index, p. 162).

As in the intercostal space, the neurovascular structures pass in the

neurovascular plane between internal oblique and transversus muscle

layers.

The rectus sheath (Fig. 11.3)

The rectus sheath encloses the rectus muscles. It contains also the super-

ior and inferior epigastric vessels and anterior rami of the lower six

thoracic nerves.

The sheath is made up from the aponeuroses of the muscles of the

anterior abdominal wall. The linea alba represents the fusion of the

aponeuroses in the midline. Throughout the major part of the length of

the rectus the aponeuroses of external oblique and the anterior layer

of internal oblique lie in front of the muscle and the posterior layer of

internal oblique and transversus behind. The composition of the sheath

is, however, different above the costal margin and above the pubic

symphysis:

• Above the costal margin: only the external oblique aponeurosis is

present and forms the anterior sheath.

• Above the pubic symphysis: about halfway between the umbilicus

and pubic symphysis the layers passing behind the rectus muscle gradu-

ally fade out and from this point all aponeuroses pass anterior to the

rectus muscle, leaving only the transversalis fascia.

The lateral border of the rectus

athelinea semilunarisacan usually

be identiﬁed in thin subjects. It crosses the costal margin in the trans-

pyloric plane.

Three tendinous intersections ﬁrmly attach the anterior sheath wall

to the muscle itself. They are situated at the level of the xiphoid, the

umbilicus and one between these two. These give the abdominal ‘six-

pack’ appearance in muscular individuals.

Arteries of the abdominal wall (Fig. 11.6)

These include the superior and inferior epigastric arteries (branches of

the internal thoracic and external iliac arteries, respectively) and the

AAAC11 21/5/05 10:43 AM Page 30

The arteries of the abdomen 31

12 The arteries of the abdomen

Fig.12.1

The abdominal aorta and its branches.

Red labels: ventral branches

Blue labels: lateral branches

Green labels: branches to body wall

Fig.12.2

The coeliac artery and its branches.

The three primary branches are labelled in red

Fig.12.3

The superior mesenteric artery and its branches

Inferior phrenic

Suprarenal

Coeliac

Superior

mesenteric

Inferior

mesenteric

Renal

Ureteric branch

Lumbar

Median sacral

Gonadal

Oesophageal

branches

Left gastric

Right gastric

Right and left hepatic

Superior

mesenteric

artery

Jejunal and

ileal branches

Cystic

Common hepatic

Gastroduodenal

Omental branch

Spleen

Splenic

Short gastric

Jejunal and

ileal branches

Ileocolic

Right colic

Middle colic

Superior

mesenteric

Appendicular

Anterior and posterior

caecal branches

Superior

pancreatico-

duodenal

Superior

pancreaticoduodenal

Inferior

pancreaticoduodenal

Right

gastro-

epiploic

Inferior

pancreatico-

duodenal

Left

gastroepiploic

Pancreatic

branches

AAAC12 21/5/05 10:43 AM Page 31

32 Abdomen and pelvis

Fig.12.4

The blood supply of the appendix

Fig.12.5

The inferior mesenteric artery and its branches.

Note the anastomosis with the inferior rectal artery (green) halfway down the anal canal

Ileocolic artery

Right colic artery

Mesentery

Ileal branch

Inferior rectal (a branch of the internal pudendal)

Anal canal

Middle colic

(from s.mesenteric)

Superior rectal

Appendicular artery

Meso-appendix

Anterior and posterior

caecal branches

Ileocaecal fold (bloodless fold of Treves)

Marginal artery

Sigmoid branches

Left colic

Inferior mesenteric

The main abdominal branches of the abdominal aorta include the:

• Coeliac trunk: supplies the embryonic foregut: from the lower third

of the oesophagus to the second part of the duodenum.

• Superior mesenteric artery: supplies the midgut: from the second

part of the duodenum to the distal transverse colon.

• Renal arteries.

• Gonadal arteries.

• Inferior mesenteric artery: supplies the hindgut: from the distal

transverse colon to the upper half of the anal canal.

The abdominal aorta (Fig. 12.1)

The abdominal aorta is a continuation of the thoracic aorta as it passes

under the median arcuate ligament of the diaphragm. It descends in the

retroperitoneum and ultimately bifurcates into left and right common

iliac arteries to the left of the midline at the level of L4. The vertebral

bodies and intervertebral discs lie behind the aorta whilst anteriorly,

from above downwards, lie its anterior branches, the coeliac plexus, the

lesser sac, the body of the pancreas, the third part of the duodenum, and

the parietal peritoneum. The main relation to the right of the abdominal

aorta is the inferior vena cava whilst to the left lie the duodenojejunal

junction and inferior mesenteric vein.

AAAC12 21/5/05 10:43 AM Page 32

The arteries of the abdomen 33

The coeliac trunk (Fig. 12.2)

This trunk arises from the aorta at the level of T12/L1 and after a short

course divides into three terminal branches. These include the:

• Left gastric artery: passes upwards to supply the lower oesophagus

by branches which ascend through the oesophageal hiatus in the

diaphragm. The left gastric then descends in the lesser omentum along

the lesser curve of the stomach which it supplies.

• Splenic artery: passes along the superior border of the pancreas

in the posterior wall of the lesser sac to reach the upper pole of the left

kidney. From here it passes to the hilum of the spleen in the lienorenal

ligament. The splenic artery also gives rise to short gastric branches,

which supply the stomach fundus, and a left gastroepiploic branch

which passes in the gastrosplenic ligament to reach and supply the

greater curve of the stomach.

• Hepatic artery: descends to the right towards the ﬁrst part of the

duodenum in the posterior wall of the lesser sac. It then passes between

the layers of the free border of the lesser omentum which conveys it to

the porta hepatis in close relation to the portal vein and bile duct (these

structures together constitute the anterior margin of the epiploic fora-

men). Before reaching the porta hepatis it divides into right and left

hepatic arteries and from the right branch the cystic artery is usually

given off. Prior to its ascent towards the porta hepatis the hepatic artery

gives rise to gastroduodenal and right gastric branches. The latter

passes along the lesser curve of the stomach to supply it. The former

passes behind the ﬁrst part of the duodenum and then branches further

into superior pancreaticoduodenal and right gastroepiploic branches.

The right gastroepiploic branch runs along the lower part of the greater

curvature to supply the stomach.

The superior mesenteric artery (Fig. 12.3)

The superior mesenteric artery arises from the abdominal aorta at the

level of L1. From above downwards, it passes over the left renal vein

behind the neck of the pancreas, over the uncinate process and anterior

to the third part of the duodenum. It then passes obliquely downwards

and towards the right iliac fossa between the layers of the mesentery of

the small intestine where it divides into its terminal branches. The

branches of the superior mesenteric artery include the:

• Inferior pancreaticoduodenal artery: supplies the lower half of the

duodenum and pancreatic head.

• Ileocolic artery: passes in the root of the mesentery over the right

ureter and gonadal vessels to reach the caecum where it divides into ter-

minal caecal and appendicular branches (Fig. 12.4).

• Jejunal and ileal branches: a total of 12 –15 branches arise from the

left side of the artery. These branches divide and reunite within the

small bowel mesentery to form a series of arcades which then give rise

to small straight terminal branches which supply the gut wall.

• Right colic artery: passes horizontally in the posterior abdominal

wall to supply the ascending colon.

• Middle colic artery: courses in the transverse mesocolon to supply

the proximal two-thirds of the transverse colon.

The renal arteries

These arise from the abdominal aorta at the level of L2.

The gonadal arteries (ovarian or testicular)

These arteries arise from below the renal arteries and descend obliquely

on the posterior abdominal wall to reach the ovary in the female, or pass

through the inguinal canal in the male to reach the testis.

The inferior mesenteric artery (Fig. 12.5)

The inferior mesenteric artery arises from the abdominal aorta at the

level of L3. It passes downwards and to the left and crosses the left

common iliac artery where it changes its name to the superior rectal

artery. Its branches include:

• The left colic artery: supplies the distal transverse colon, the splenic

ﬂexure and upper descending colon.

• Two or three sigmoid branches: pass into the sigmoid mesocolon

and supply the lower descending and sigmoid colon.

• The superior rectal artery: passes into the pelvis behind the rectum

to form an anastomosis with the middle and inferior rectal arteries. It

supplies the rectum and upper half of the anal canal.

The marginal artery (of Drummond) is an anastomosis of the colic

arteries at the margin of the large intestine. This establishes a strong

collateral circulation throughout the colon.

AAAC12 21/5/05 10:43 AM Page 33

34 Abdomen and pelvis

13 The veins and lymphatics of the abdomen

Fig.13.1

The inferior vena cava and its tributaries

Fig.13.2

The portal system.

Note the anastomoses with the systemic system (orange) in the oesophagus and the anal canal

Inferior phrenic

Suprarenal

Ureteric branch

Renal

Lumbar

Median sacral

Common iliac

Gonadal

Pancreaticoduodenal

Right colic

Middle colic

Cystic

Oesophageal branches

Right gastric

Left gastric

Right gastroepiploic

Spleen

Splenic

Inferior mesenteric

Superior mesenteric

Left colic

Sigmoid branches

Superior rectal

Portal vein

AAAC13 21/5/05 10:42 AM Page 34

The portal vein (Fig. 13.2)

The portal venous system receives blood from the length of gut from

the lower third of the oesophagus to the upper half of the anal canal as

well as the spleen, pancreas and gall-bladder. It serves to transfer blood

to the liver where the products of digestion can be metabolized and

stored. Blood from the liver ultimately gains access to the inferior vena

cava by way of the hepatic veins. The portal vein is formed behind the

neck of the pancreas by the union of the superior mesenteric and splenic

veins. It passes behind the ﬁrst part of the duodenum in front of the in-

ferior vena cava and enters the free border of the lesser omentum. The

vein then ascends towards the porta hepatis in the anterior margin of the

epiploic foramen (of Winslow) in the lesser omentum. At the porta hep-

atis it divides into right and left branches. The veins that correspond to

the branches of the coeliac and superior mesenteric arteries drain into

the portal vein or one of its tributaries. The inferior mesenteric vein

drains into the splenic vein adjacent to the fourth part of the duodenum.

Porto-systemic anastomoses

A number of connections occur between the portal and systemic circula-

tions. When the direct pathway through the liver becomes congested

(such as in cirrhosis) the pressure within the portal vein rises and under

these circumstances the porto-systemic anastomoses form an alternat-

ive route for the blood to take. The sites of porto-systemic anastomosis

include:

• The lower oesophagus (p. 11): formed by tributaries of the left gas-

tric (portal) and oesophageal veins (systemic via the azygos and hemi-

azygos veins).

• The anal canal: formed by the superior rectal (portal) and middle

and inferior rectal veins (systemic).

• The bare area of the liver: formed by the small veins of the portal

system and the phrenic veins (systemic).

• The periumbilical region: formed by small paraumbilical veins

which drain into the left portal vein and the superﬁcial veins of the anter-

ior abdominal wall (systemic).

The inferior vena cava (Fig. 13.1)

The inferior vena cava is formed by the union of the common iliac veins

in front of the body of L5. It ascends in the retroperitoneum on the right

side of the abdominal aorta. Along its course, from below upwards, it

forms the posterior wall of the epiploic foramen of Winslow and is

embedded in the bare area of the liver in front of the right suprarenal

gland. The inferior vena cava passes through the caval opening in the

diaphragm at the level of T8 and drains into the right atrium.

The lymphatic drainage of the abdomen and pelvis

The abdominal wall

Lymph from the skin of the anterolateral abdominal wall above the

level of the umbilicus drains to the anterior axillary lymph nodes. Effer-

ent lymph from the skin below the umbilicus drains to the superﬁcial

inguinal nodes.

The lymph nodes and trunks

The two main lymph node groups of the abdomen are closely related to

the aorta. These comprise the pre-aortic and para-aortic groups.

• The pre-aortic nodes are arranged around the three ventral branches

of the aorta and consequently receive lymph from the territories that are

supplied by these branches. This includes most of the gastrointestinal

tract, liver, gall-bladder, spleen and pancreas. The efferent vessels from

the pre-aortic nodes coalesce to form a variable number of intestinal

trunks which deliver the lymph to the cisterna chyli.

• The para-aortic nodes are arranged around the lateral branches of the

aorta and drain lymph from their corresponding territories, i.e. the kid-

neys, adrenals, gonads, and abdominal wall as well as the common iliac

nodes. The efferent vessels from the para-aortic nodes coalesce to form

a variable number of lumbar trunkswhich deliver the lymph to the cis-

terna chyli.

Cisterna chyli

The cisterna chyli is a lymphatic sac that lies anterior to the bodies of

the 1st and 2nd lumbar vertebrae. It is formed by the conﬂuence of the

intestinal trunks, the lumbar trunks and lymphatics from the lower tho-

racic wall. It serves as a receptacle for lymph from the abdomen and

lower limbs which is then relayed to the thorax by the thoracic duct

(p. 11).

The lymphatic drainage of the stomach

Lymph from the stomach drains to the coeliac nodes. For the purposes

of description, the stomach can be divided into four quarters where

lymph drains to the nearest appropriate group of nodes.

The lymphatic drainage of the testes

Lymph from the skin of the scrotum and the tunica albuginea drains to

the superﬁcial inguinal nodes. Lymph from the testes, however, drains

along the course of the testicular artery to the para-aortic group of

nodes. Hence, a malignancy of the scrotal skin might result in palpable

enlargement of the superﬁcial inguinal nodes whereas testicular

tumours metastasize to the para-aortic nodes.

The veins and lymphatics of the abdomen 35

AAAC13 21/5/05 10:42 AM Page 35

36 Abdomen and pelvis

14 The peritoneum

Fig.14.1

A vertical section through the abdomen to show the

peritoneal relations.

Lesser sac

Greater sac

Fig.14.2

A horizontal section through the abdomen.

Note how the epiploic foramen lies between two major veins

Fig.14.3

The peritoneal relations of the liver

(a) Seen from in front

(b) The same liver rotated in the direction of the arrow to show the upper and posterior surfaces.

The narrow spaces between the liver and the diaphragm labelled A and B are the right and left subphrenic spaces

Upper recess of

omental bursa

Diaphragm

Transverse mesocolon

Small intestine

Mesentery

Liver

Epiploic foramen

(in the distance)

Greater omentum

Subphrenic space

Epiploic foramen (of Winslow)

Aorta

Left kidney

Splenic artery

Lienorenal ligament

Spleen

Short gastric

vessels

Gastrosplenic

ligament

Stomach

Lesser omentum

Duodenum (third part)

Transverse colon

Fusion between layers

of greater omentum

Lesser omentum

Pancreas

Stomach

Omental bursa

Portal vein

Inferior vena cava

Hepatic artery

Common bile duct

Liver

(a)

(b)

Peritoneum

covering

caudate lobe

Lower layer of

coronary ligament

Right

triangular

ligament

Left triangular

ligament

Inferior vena cava

Upper layer of

coronary ligament

Upper layer of

coronary ligament

Bare area

Falciform ligament

Gall bladder

Ligamentum teres

Position of umbilicus

Ligamentum teres

Portal vein, hepatic

artery and bile duct

in free edge of lesser

omentum leading to

porta hepatis

Cut edge of lesser

omentum

Fissure for

ligamentum venosum

Left triangular

ligament

Fundus of

gall bladder

AAAC14 21/5/05 10:42 AM Page 36

The mesenteries and layers of the peritoneum

The transverse colon, stomach, spleen and liver each have attached to

them two‘mesenteries’

adouble layers of peritoneum containing arteries

and their accompanying veins, nerves and lymphatics

awhile the small

intestine and sigmoid colon have only one. All the other viscera are re-

troperitoneal. The mesenteries and their associated arteries are as follows:

• The colon ( Fig. 14.1): (1) The transverse mesocolon (the middle

colic artery). (2) The posterior two layers of the greater omentum.

• The stomach ( Fig. 14.1): (1) The lesser omentum (the left and right

gastric arteries and in its free border, the hepatic artery, portal vein and

bile duct). (2) The anterior two layers of thegreater omentum (the right

and left gastroepiploic arteries and their omental branches).

• The spleen ( Fig. 14.2): (1) The lienorenal ligament (the splenic

artery). (2) The gastrosplenic ligament (the short gastric and left gas-

troepiploic arteries).

• The liver (Fig. 14.3): (1) The falciform ligament and the two layers

of the coronary ligamentwith their sharp edges, the left and right trian-

gular ligaments. This mesentery is exceptional in that the layers of the

coronary ligament are widely separated so that the liver has a bare area

directly in contact with the diaphragm (the obliterated umbilical artery

in the free edge of the falciform ligament and numerous small veins in

the bare area, p. 35). (2) Thelesser omentum (already described).

• The small intestine (Fig. 14.1): (1) The mesentery of the small intes-

tine(the superior mesenteric artery and its branches).

• The sigmoid colon: (1) The sigmoid mesocolon (the sigmoid arteries

and their branches).

The peritoneal cavity (Figs 14.1 and 14.2)

• The complications of the peritoneal cavity may best be described by

starting at the transverse mesocolon. Its two layers are attached to the

anterior surface of the pancreas, the second part of the duodenum and

the front of the left kidney. They envelop the transverse colon and con-

tinue downwards to form the posterior two layers of the greater omen-

tum, which hangs down over the coils of the small intestine. They then

turn back on themselves to form the anterior two layers of the omentum

and these reach the greater curvature of the stomach. The four layers of

the omentum are fused and impregnated with fat. The greater omentum

plays an important role in limiting the spread of infection in the peri-

toneal cavity.

• From its attachment to the pancreas, the lower layer of the transverse

mesocolon turns downwards to become the parietal peritoneum of the

posterior abdominal wall from which it is reﬂected to form the mesen-

tery of the small intestine and thesigmoid mesocolon.

• The upper layer of the transverse mesocolon passes upwards to form

the parietal peritoneum of the posterior abdominal wall, covering the

upper part of the pancreas, the left kidney and its suprarenal, the aorta

and the origin of the coeliac artery (the ‘stomach bed’). It thus forms the

posterior wall of the omental bursa. It then covers the diaphragm and

continues onto the anterior abdominal wall.

• From the diaphragm and anterior abdominal wall it is reﬂected onto

the liver to form its ‘mesentery’ in the form of the two layers of the fal-

ciform ligament. At the liver, the left layer of the falciform ligament

folds back on itself to form the sharp edge of the left triangular liga-

ment while the right layer turns back on itself to form the upper and

lower layers of the coronary ligament with its sharp-edged right tri-

angular ligament. The layers of the coronary ligament are widely

separated so that a large area of liver between them

athe bare areaa

is directly in contact with the diaphragm. The inferior vena cava is

embedded in the bare area (Fig. 14.3).

• From the undersurface of the liver another ‘mesentery’ passes from

the ﬁssure for the ligamentum venosum to the lesser curvature of the

stomach to form the lesser omentum.

• The lesser omentum splits to enclose the stomach and is continuous

with the two layers of the greater omentum already described. The

lesser omentum has a right free border which contains the portal vein,

the hepatic artery and the common bile duct.

• In the region of the spleen there are two more ‘mesenteries’ which are

continuous with the lesser and greater omenta. These are the lienorenal

ligament, a double layer of peritoneum reﬂected from the front of the

left kidney to the hilum of the spleen, and the gastrosplenic ligament

which passes from the hilum of the spleen to the greater curvature of the

stomach (Fig. 14.2).

• The mesentery of the small intestine is attached to the posterior ab-

dominal wall from the duodenojejunal ﬂexure to the ileocolic junction.

• The sigmoid mesocolon passes from a V-shaped attachment on the

posterior abdominal wall to the sigmoid colon.

• The general peritoneal cavity comprises the main cavity

athe greater

sac

aand a diverticulum from itathe omental bursa (lesser sac). The

omental bursa lies between the stomach and the stomach bed to allow

free movement of the stomach. It lies behind the stomach, the lesser

omentum and the caudate lobe of the liver and in front of the structures

of the stomach bed. The left border is formed by the hilum of the spleen

and the lienorenal and gastrosplenic ligaments.

• The communication between the greater and lesser sacs is the epi-

ploic foramen (foramen of Winslow). It lies behind the free border of

the lesser omentum and its contained structures, below the caudate pro-

cess of the liver, in front of the inferior vena cava and above the ﬁrst

part of the duodenum.

• The subphrenic spaces are part of the greater sac that lies between the

diaphragm and the upper surface of the liver. There are right and left

spaces, separated by the falciform ligament.

• In the pelvis the parietal peritoneum covers the upper two-thirds of

the rectum whence it is reﬂected, in the female, onto the posterior

fornix of the vagina and the back of the uterus to form the recto-uterine

pouch (pouch of Douglas). In the male it passes onto the back of the

bladder to form therectovesical pouch.

The anterior abdominal wall

• The peritoneum of the deep surface of the anterior abdominal wall

shows a central ridge from the apex of the bladder to the umbilicus pro-

duced by the median umbilical ligament. This is the remains of the

embryonic urachus. Two medial umbilical ligaments converge to the

umbilicus from the pelvis. They represent the obliterated umbilical

arteries of the fetus. The ligamentum teresis a ﬁbrous band in the free

margin of the falciform ligament. It represents the obliterated left

umbilical vein.

The peritoneum 37

AAAC14 21/5/05 10:42 AM Page 37

38 Abdomen and pelvis

15 The upper gastrointestinal tract I

Fig.15.1

The subdivisions of the stomach

Fig.15.2

The stomach bed. For more detail see fig.19.1.

The stomach is outlined but the shape is by no means constant

Duodenum

Right crus of diaphragm

Suprarenal

Pyloric sphincter

Angular incisure

Lesser curvature

Cardiac notch

Fundus

Body

Greater curvature

Pyloric antrum

Right kidney

Spleen

Aorta

Splenic artery

Splenic flexure of colon

Pancreas

Left kidney

Descending colon

Hepatic

flexure

Ascending

colon

AAAC15 21/5/05 10:42 AM Page 38

The embryonic gut is divided into foregut, midgut and hindgut, sup-

plied, respectively, by the coeliac, superior mesenteric and inferior

mesenteric arteries. The foregut extends from the oesophagus to the

entrance of the common bile duct into the second part of the duodenum.

The midgut extends down to two-thirds of the way along the transverse

colon. It largely develops outside the abdomen until this congenital

‘umbilical hernia’ is reduced during the 8th–10th week of gestation.

The hindgut extends down to include the upper half of the anal canal.

The abdominal oesophagus

• The abdominal oesophagus measures approximately 1cm in length.

• It is accompanied by the anterior and posterior vagal trunks from the

left and right vagi and the oesophageal branches of the left gastric

artery.

• The lower third of the oesophagus is a site of porto-systemic venous

anastomosis. This is formed between tributaries of the left gastric and

azygos veins (p. 11).

The stomach (Figs 15.1 and 15.2)

• The notch on the lesser curve, at the junction of the body and pyloric

antrum, is the incisura angularis.

• The pyloric sphincter controls the release of stomach contents into

the duodenum. The sphincter is composed of a thickened layer of circu-

lar smooth muscle which acts as an anatomical, as well as physiolo-

gical, sphincter. The junction of the pylorus and duodenum can be seen

externally as a constriction with an overlying vein

athe prepyloric vein

(ofMayo).

• The cardiac oriﬁce represents the point of entry for oesophageal con-

tents into the stomach. The cardiac sphincter acts to prevent reﬂux of

stomach contents into the oesophagus. Unlike the pylorus there is no

discrete anatomical sphincter at the cardia; however, multiple factors

contribute towards its mechanism. These include: the arrangement of

muscle ﬁbres at the cardiac oriﬁce acting as a physiological sphincter;

the angle at which the oesophagus enters the stomach producing a valve

effect; the right crus of the diaphragm surrounding the oesophagus and

compression of the short segment of intra-abdominal oesophagus by in-

creases in intra-abdominal pressure during straining, preventing reﬂux.

• The lesser omentum is attached to the lesser curvature and the greater

omentum to the greater curvature. The omenta contain the blood and

lymphatic supply to the stomach.

• The mucosa of the stomach is thrown into folds

arugae.

• Blood supply (see Fig. 12.2): the arterial supply to the stomach is

exclusively from branches of the coeliac axis. Venous drainage is to the

portal system (see Fig. 13.2).

• Nerve supply: the anterior and posterior vagal trunks arise from the

oesophageal plexuses and enter the abdomen through the oesophageal

hiatus. The hepaticbranches of the anterior vagus pass to the liver. The

coeliac branch of the posterior vagus passes to the coeliac ganglion

from where it proceeds to supply the intestine down to the distal trans-

verse colon. The anterior and posterior vagal trunks descend along the

lesser curve as the anterior and posterior nerves of Latarjetfrom which

terminal branches arise to supply the stomach. The vagi provide a

motor and secretory supply to the stomach. The latter includes a supply

to the acid-secreting part

athe body.

The duodenum (Figs 19.1 and 19.2)

The duodenum is the ﬁrst part of the small intestine. It is approximately

25cm long and curves around the head of the pancreas. Its primary

function is in the absorption of digested products. Despite its relatively

short length the surface area is greatly enhanced by the mucosa being

thrown into folds bearing villi which are visible only at a microscopic

level. With the exception of the ﬁrst 2.5cm, which is completely cov-

ered by peritoneum, the duodenum is a retroperitoneal structure. It is

considered in four parts:

• First part (5 cm).

• Second part (7.5 cm)

athis part descends around the head of the

pancreas. Internally, in the mid-section, a small eminence may be

found on the posteromedial aspect of the mucosa

athe duodenal

papilla. This structure represents the site of the common opening

of the bile duct and main pancreatic duct (of Wirsung). The sphinc-

ter of Oddi guards this common opening. A smaller subsidiary

pancreatic duct (of Santorini) opens into the duodenum a small

distance above the papilla.

• Third part (10 cm)

athis part is crossed anteriorly by the root of

the mesentery and superior mesenteric vessels.

• Fourth part (2.5 cm)

athis part terminates as the duodenojejunal

junction. The termination of the duodenum is demarcated by a

peritoneal fold stretching from the junction to the right crus of

the diaphragm covering the suspensory ligament of Treitz. The

terminal part of the inferior mesenteric vein lies adjacent to the

duodenojejunal junction and serves as a useful landmark.

• Blood supply (see Fig. 12.2): the superior and inferior pancreatico-

duodenal arteries supply the duodenum and run between this structure

and the pancreatic head. The superior artery arises from the coeliac axis

and the inferior from the superior mesenteric artery.

Peptic ulcer disease

Most peptic ulcers occur in the stomach and proximal duodenum. They

arise as a result of an imbalance between acid secretion and mucosal

defences. Helicobacter pylori infection is a signiﬁcant aetiological

factor and the eradication of this organism, as well as the attenuation

of acid secretion, form the cornerstones of medical treatment. In a

minority of cases the symptoms are not controlled by medical treatment

alone and surgery is required. ‘Very highly selective vagotomy’ is a

technique where only the afferent vagal ﬁbres to the acid-secreting

body are denervated thus not compromising the motor supply to the

stomach and hence bypassing the need for a drainage procedure (e.g.

gastrojejunostomy).

The upper gastrointestinal tract I 39

AAAC15 21/5/05 10:42 AM Page 39

40 Abdomen and pelvis

16 The upper gastrointestinal tract II

Thicker wall

(feels full)

Jejunal branches

Redder

wall

Ileal branches

From superior mesenteric artery

Thinner wall

(feels empty)

Simple arcades Multiple arcades

Fig.16.1

The jejunum and the ileum can be distinguished by their colour, feel and the complexity of the arterial arcades

Fig.16.2

Small bowel obstruction, showing dilated bowel loops

Jejunum Ileum

AAAC16 21/5/05 10:41 AM Page 40

The small intestine (Fig. 16.1)

The small intestine is approximately 6m long and comprises the duo-

denum, jejunum and ileum. A large internal surface area throughout the

small intestine facilitates absorption of digested products. The small

intestine is suspended from the posterior abdominal wall by its mesen-

tery which contains the superior mesenteric vessels, lymphatics and auto-

nomic nerves. The origin of the mesentery measures approximately 15

cm and passes from the duodenojejunal ﬂexure to the right sacro-iliac

joint. The distal border is obviously the same length as the intestine.

No sharp distinction occurs between the jejunum and ileum; however,

certain characteristics help distinguish between them:

• Excluding the duodenum, the proximal two-ﬁfths of the small intes-

tine comprises jejunum whereas the remaining distal three-ﬁfths com-

prises ileum. Loops of jejunum tend to occupy the umbilical region

whereas the ileum occupies the lower abdomen and pelvis.

• The mucosa of the small intestine is thrown into circular folds

athe

valvulae conniventes. These are more prominent in the jejunum than in

the ileum.

• The diameter of the jejunum tends to be greater than that of the ileum.

• The mesentery to the jejunum tends to be thicker than that for the

ileum.

• The superior mesenteric vessels (see Fig. 12.3) pass over the third

part of the duodenum to enter the root of the mesentery and pass

towards the right iliac region on the posterior abdominal wall. Jejunal

and ileal branches arise which divide and re-anastomose within the

mesentery to produce arcades. End-artery vessels arise from the

arcades to supply the gut wall. The arterial supply to the jejunum con-

sists of few arcades and little terminal branching whereas the vessels to

the ileum form numerous arcades and much terminal branching of end-

arteries passing to the gut wall.

Small bowel obstruction (Fig. 16.2)

Small bowel obstruction (SBO) can occur due to luminal, mural or

extraluminal factors that result in luminal blockage. Post surgical

adhesions and herniae are the most frequent causes. Many cases

resolve with conservative measures only; however, if any deterioration

in the clinical picture occurs to suggest intestinal infarction or perfora-

tion an exploratory laparotomy is mandatory. The classical X-ray fea-

tures of SBO are those of dilated small bowel loops. These can be

distinguished from large bowel as the valvulae conniventes (present

only in the small bowel) can be identiﬁed traversing the entire lumen

whereas the small bowel haustra only partially traverse the lumen.

The upper gastrointestinal tractII 41

AAAC16 21/5/05 10:41 AM Page 41

42 Abdomen and pelvis

17 The lower gastrointestinal tract

Teniae coli

Fig.17.2

A coronal section through the pelvis to show the

anal sphincters and the ischiorectal fossa

Fig.17.1

The various positions in which the appendix may be found.

In the pelvic position the appendix may be close to the ovary in the female

Appendices

epiploicae

Retrocaecal

Pelvic

Subcaecal

Ovary in female

Rectum

Longitudinal muscle

Submucosa

Sphincter ani internus

Pre-ileal

Retro-ileal

Retrocolic

Circular muscle

Levator ani

Obturator internus

Fat of ischiorectal fossa

Sphincter

ani

externus

Deep

Superficial

Subcutaneous

Pudendal canal

Adductor muscles

Inferior rectal

vesels and nerve

AAAC17 21/5/05 10:40 AM Page 42

The caecum and colon (Figs 17.1, 12.3, 12.5)

In adults, the large bowel measures approximately 1.5m. The caecum,

ascending, transverse, descending and sigmoid colon have similar

characteristic features. These are that they possess:

• Appendices epiploicae ( Fig. 17.1): these are fat-laden peritoneal tags

present over the surface of the caecum and colon.

• Teniae coli ( Fig. 17.1): these are three ﬂattened bands representing

the condensed longitudinal muscular coat of the large intestine. They

course from the base of the appendix (and form a useful way of locating

this structure at operation) to the recto-sigmoid junction.

• Sacculations: because the teniae are shorter than the bowel itself the

colon takes on a sacculated appearance. These sacculations are visible

not only at operation but also radiographically. On a plain abdominal X-

ray, the colon, which appears radiotranslucent because of the gas within,

has shelf-like processes (haustra) which partially project into the lumen.

The transverse and sigmoid colon are each attached to the posterior

abdominal wall by their respective mesocolons and are covered en-

tirely by peritoneum. Conversely, the ascending and descending colon

normally possess no mesocolon. They are adherent to the posterior

abdominal wall and covered only anteriorly by peritoneum.

The appendix (Fig. 17.1)

The appendix varies enormously in length but in adults it is approxim-

ately 5–15 cm long. The base of the appendix arises from the postero-

medial aspect of the caecum; however, the lie of the appendix itself is

highly variable. In most cases the appendix lies in the retrocaecal posi-

tion but other positions frequently occur. The appendix has the follow-

ing characteristic features:

• It has a small mesentery which descends behind the terminal ileum.

The only blood supply to the appendix, the appendicular artery (a

branch of the ileocolic), courses within its mesentery (see Fig. 12.4). In

cases of appendicitis the appendicular artery ultimately thromboses.

When this occurs, gangrene and perforation of the appendix inevitably

supervene.

• The appendix has a lumen which is relatively wide in infants and gra-

dually narrows throughout life, often becoming obliterated in the elderly.

• The teniae coli of the caecum lead to the base of the appendix.

• The bloodless fold of Treves (ileocaecal fold) is the name given to a

small peritoneal reﬂection passing from the anterior terminal ileum to

the appendix. Despite its name it is not an avascular structure!

Appendicectomy is performed most commonly through a grid-iron

muscle-splitting incision. The appendix is ﬁrst located and then deliv-

ered into the wound. The mesentery of the appendix is then divided and

ligated. The appendix is then tied at its base, excised and removed.

Most surgeons still opt to invaginate the appendix stump as a precau-

tionary measure against slippage of the stump ligature.

The rectum (Figs 17.2, 12.5)

• The rectum measures 10 –15 cm in length. It commences in front of

the 3rd sacral vertebra as a continuation of the sigmoid colon and fol-

lows the curve of the sacrum anteriorly. It turns backwards abruptly in

front of the coccyx to become the anal canal.

• The mucosa of the rectum is thrown into three horizontal folds that

project into the lumen

athe valves of Houston.

• The rectum lacks haustrations. The teniae coli fan out over the rec-

tum to form anterior and posterior bands.

• The rectum is slightly dilated at its lower end

athe ampulla, and is

supported laterally by the levator ani.

• Peritoneum covers the upper two-thirds of the rectum anteriorly but

only the upper third laterally. In the female it is reﬂected forwards onto

the uterus forming the recto-uterine pouch (pouch of Douglas). The

rectum is separated from anterior structures by a tough fascial sheet

athe rectovesical (Denonvilliers) fascia.

The anal canal (Fig. 17.2)

The anorectal junction is slung by the puborectalis component of lev-

ator ani which pulls it forwards. The canal is approximately 4cm long

and angled postero-inferiorly. Developmentally the midpoint of the

anal canal is represented by the dentate line. This is the site where the

proctodeum (ectoderm) meets endoderm. This developmental implica-

tion is reﬂected by the following characteristics of the anal canal:

• The epithelium of the upper half of the anal canal is columnar. In con-

trast the epithelium of the lower half of the anal canal is squamous. The

mucosa of the upper canal is thrown into vertical columns (of Mor-

gagni). At the bases of the columns are valve-like folds (valves of Ball).

The level of the valves is termed the dentate line.

• The blood supply to the upper anal canal (see Fig. 12.5) is from the

superior rectal artery (derived from the inferior mesenteric artery)

whereas the lower anal canal is supplied by the inferior rectal artery

(derived from the internal iliac artery). As mentioned previously, the

venous drainage follows suit and represents a site of porto-systemic

anastomosis (see p. 35).

• The upper anal canal is insensitive to pain as it is supplied by auto-

nomic nerves only. The lower anal canal is sensitive to pain as it is sup-

plied by somatic innervation (inferior rectal nerve).

• The lymphatics from the upper canal drain upwards along the super-

ior rectal vessels to the internal iliac nodes whereas lymph from the

lower anal canal drains to the inguinal nodes.

The anal sphincter

See Chapter 25.

The lower gastrointestinal tract 43

AAAC17 21/5/05 10:40 AM Page 43

44 Abdomen and pelvis

18 The liver, gall-bladder and biliary tree

Fig.18.1

The venous circulation through the liver.

The transmission of blood from the portal system to the inferior vena cava

is via the liver lobules (fig. 18.2)

Fig.18.2

(a) A liver lobule to show the direction of blood flow from the portal system to the centrilobular veins

and thence to the inferior vena cava

(b) The blood flow through the sinusoids of the liver lobule and the passage of bile from the bile

canaliculi to the bile ducts

Opening in central tendon

of diaphragm

Portal vein

Liver

Spleen

Splenic vein

Bile canaliculi

Bile duct

Branch of hepatic artery

Branch of portal vein

Periportal

connective

tissue

Direction of

bile flow

Bile duct

Inferior mesenteric vein

Superior mesenteric vein

(a) (b)

Hepatic vein

Direction of blood flow

Artery

Sinusoids

Vein

Central vein

AAAC18 21/5/05 10:40 AM Page 44

The liver (see Fig. 14.3)

• The liver predominantly occupies the right hypochondrium but the

left lobe extends to the epigastrium. Its domed upper (diaphragmatic)

surface is related to the diaphragm and its lower border follows the con-

tour of the right costal margin. When the liver is enlarged the lower

border becomes palpable below the costal margin.

• The liver anatomically consists of a large right lobe, and a smaller left

lobe. These are separated antero-superiorly by the falciform ligament

and postero-inferiorly by ﬁssures for theligamentum venosum and liga-

mentum teres. In the anatomical classiﬁcation the right lobe includes

the caudate and quadrate lobes. Functionally, however, the caudate and

most of the quadrate lobes are units of the left lobe as they receive their

blood supplies from the left hepatic artery and deliver their bile into the

left hepatic duct. Hence, the functional classiﬁcation of the liver deﬁnes

the right and left lobes as separated by a vertical plane extending pos-

teriorly from the gall-bladder to the inferior vena cava (IVC).

• When the postero-inferior (visceral) surface of the liver is seen from

behind an H-shaped arrangement of grooves and fossae is identiﬁed.

The boundaries of the H are formed as follows:

• Right anterior limb

athe gall-bladder fossa.

• Right posterior limb

athe groove for the IVC.

• Left anterior limb

athe ﬁssure containing the ligamentum teres

(the fetal remnant of the left umbilical vein which returns oxygen-

ated blood from the placenta to the fetus).

• Left posterior limb

athe ﬁssure for the ligamentum venosum (the

latter structure is the fetal remnant of the ductus venosus; in the

fetus the ductus venosus serves to partially bypass the liver by

transporting blood from the left umbilical vein to the IVC).

• Horizontal limb

athe porta hepatis. The caudate and quadrate

lobes of the liver are the areas deﬁned above and below the hori-

zontal bar of the H, respectively.

• The porta hepatis is the hilum of the liver. It transmits (from pos-

terior to anterior) the: portal vein (Fig. 18.1); branches of the hepatic

artery and hepatic ducts. The porta is enclosed within a double layer of

peritoneum

athe lesser omentum, which is ﬁrmly attached to the liga-

mentum venosum in its ﬁssure.

• The liver is covered by peritoneum with the exception of the ‘bare

area’.

• The liver is made up of multiple functional units

alobules (Fig. 18.2).

Branches of the portal vein and hepatic artery transport blood through

portal canals into a central vein by way of sinusoids which traverse the

lobules. The central veins ultimately coalesce into the right, left and

central hepatic veins which drain blood from corresponding liver areas

backwards into the IVC. The portal canals also contain tributaries of the

hepatic ducts which serve to drain bile from the lobule down the biliary

tree from where it can be concentrated in the gall-bladder and eventu-

ally released into the duodenum. The extensive length of gut that is

drained by the portal vein explains the predisposition for intestinal

tumours to metastasize to the liver.

The gall-bladder (see Fig. 14.3)

The gall-bladder lies adherent to the undersurface of the liver in the

transpyloric plane (p. 53) at the junction of the right and quadrate lobes.

The duodenum and the transverse colon are behind it.

The gall-bladder acts as a reservoir for bile which it concentrates.

It usually contains approximately 50mL of bile which is released

through the cystic and then common bile ducts into the duodenum in

response to gall-bladder contraction induced by gut hormones.

• Structure: the gall-bladder comprises a fundus, a body and a neck

(which opens into the cystic duct).

• Blood supply: the arterial supply to the gall-bladder is derived from

two sources: the cystic artery which is usually, but not always, a branch

of the right hepatic artery, and small branches of the hepatic arteries

which pass via the fossa in which the gall-bladder lies. The cystic artery

represents the most signiﬁcant source of arterial supply. There is, how-

ever, no corresponding cystic vein but venous drainage occurs via

small veins passing through the gall-bladder bed.

The biliary tree

The common hepatic duct is formed by the conﬂuence of the right and

left hepatic ducts in the porta hepatis. The common hepatic duct is

joined by the cystic duct to form the common bile duct. This structure

courses, sequentially, in the free edge of the lesser omentum, behind the

ﬁrst part of the duodenum and in the groove between the second part of

the duodenum and the head of the pancreas. It ultimately opens at the

papilla on the medial aspect of the second part of the duodenum.

The common bile duct usually, but not always, joins with the main

pancreatic duct (of Wirsung)(p. 47).

Cholelithiasis

Gallstones are composed of either cholesterol, bile pigment, or, more

commonly, a mixture of these two constituents. Cholesterol stones form

due to an altered composition of bile resulting in the precipitation of

cholesterol crystals. Most gallstones are asymptomatic; however,

when they migrate down the biliary tree they can be responsible for a

diverse array of complications such as: acute cholecystitis, biliary

colic, cholangitis and pancreatitis.

The liver, gall-bladder and biliary tree 45

AAAC18 21/5/05 10:40 AM Page 45

46 Abdomen and pelvis

19 The pancreas and spleen

Fig.19.1

The relations of the pancreas

Fig.19.2

The ducts of the pancreas and the biliary system

Fig.19.3

The relations of the spleen

Inferior vena cava

Right and left hepatic ducts

Right gastroepiploic artery

Superior

pancreaticoduodenal artery

Inferior

pancreaticoduodenal artery

Superior mesenteric

artery and vein

Portal vein

Common bile duct

Hepatic artery

Right gastric artery

Gastroduodenal artery

Left gastric artery

Coeliac artery

Splenic artery

Inferior mesenteric

artery and vein

Cystic duct

Right hepatic artery

Pancreatic duct

(of Wirsung)

Tail of pancreas

Body

Neck

Superior

mesenteric vessels

Common bile duct

Neck

Body

Gall bladder

(displaced)

Uncinate process

Fundus

Duodenal papilla

(of Vater)

Accessory duct

(of Santorini)

Spleen

Diaphragm

Ribs 9,

10 and 11

Splenic

artery

Tail of

pacreas

Left kidney

and suprarenal

Splenic flexure

of colon

Cystic artery

AAAC19 21/5/05 10:39 AM Page 46

The pancreas (Figs 19.1 and 19.2)

The pancreas has a: head, neck, body and tail. It is a retroperitoneal

organ which lies roughly along the transpyloric plane. The head is

bound laterally by the curved duodenum and the tail extends to the

hilum of the spleen in the lienorenal ligament. The superior mesenteric

vessels pass behind the pancreas, then anteriorly, over the uncinate

process and third part of the duodenum into the root of the small bowel

mesentery. The inferior vena cava, aorta, coeliac plexus, left kidney

(and its vessels) and the left adrenal gland are posterior pancreatic rela-

tions. In addition, the portal vein is formed behind the pancreatic neck

by the conﬂuence of the splenic and superior mesenteric veins. The

lesser sac and stomach are anterior pancreatic relations.

• Structure: the main pancreatic duct (of Wirsung) courses the length

of the gland, ultimately draining pancreatic secretions into the ampulla

of Vater, together with the common bile duct, and thence into the sec-

ond part of the duodenum. An accessory duct (of Santorini)drains the

uncinate process of the pancreas, opening slightly proximal to the

ampulla into the second part of the duodenum.

• Blood supply: the pancreatic head receives its supply from the

superior and inferior pancreaticoduodenal arteries. The splenic artery

courses along the upper border of the body of the pancreas which it sup-

plies by means of a large branch

athearteria pancreatica magnaaand

numerous smaller branches.

• Function: the pancreas is a lobulated structure which performs both

exocrine and endocrine functions. The exocrine secretory glands drain

pancreatic juice into the pancreatic ducts and, from there, ultimately

into the duodenum. The secretion is essential for the digestion and

absorption of proteins, fats and carbohydrates. The endocrine pancreas

is responsible for the production and secretion of glucagon and insulin,

which take place in specialized cells of the islets of Langerhans.

Acute pancreatitis

The presence of gallstones and a history of excessive alcohol intake are

the predominant associations for pancreatitis. The mechanism by

which these aetiological factors result in pancreatic injury is unknown;

however, they both appear to result in activation of pancreatic exocrine

pro-enzymes with resultant autodigestion. Even today, the mortality

rate for severe acute pancreatitis remains in the region of 20%.

The spleen (Fig. 19.3)

The spleen is approximately the size of a clenched ﬁst and lies directly

below the left hemidiaphragm which, in addition to the pleura, separ-

ates it from the overlying 9th, 10th and 11th ribs.

• Peritoneal attachments: the splenic capsule is ﬁbrous with peri-

toneum adherent to its surface. The gastrosplenic and lienorenal liga-

ments attach it to the stomach and kidney, respectively. The former

ligament carries the short gastric and left gastroepiploic vessels to the

fundus and greater curvature of the stomach, and the latter ligament

carries the splenic vessels and tail of the pancreas towards the left

kidney.

• Blood supply: is from the splenic artery to the hilum of the spleen.

Venous drainage is to the splenic vein, thence to the portal vein.

• Structure: the spleen is a highly vascular reticulo-endothelial organ.

It consists of a thin capsule from which trabeculae extend into the

splenic pulp. In the spleen, the immunological centres, i.e. the lym-

phoid follicles (the white pulp), are scattered throughout richly vascu-

larized sinusoids (the red pulp).

Splenectomy

As the spleen is a highly vascular organ, any injury to it can be life-

threatening. Under these circumstances splenectomy must be carried

out urgently. The technique used differs slightly when the procedure is

performed for emergency as opposed to elective indications, but the

principles are similar. Splenectomy involves: ligature of the splenic

vessels approaching the hilum (taking care not to injure the tail of the

pancreas or colon); and dissection of the splenic pedicles

bthe gastro-

splenic (including the short gastric vessels) and lienorenal ligaments.

As the spleen is an important immunological organ, postsplenectomy

patients are rendered immunocompromised to capsulated bacteria.

The latter organisms (e.g. meningococcus, pneumococcus) require

opsonization for elimination and splenic lymphoid follicles are the

principal sites where this takes place. Hence, following splenectomy,

all patients are routinely vaccinated against the capsulated bacteria,

and children, who are the group most at risk of sepsis, are maintained

on long-term antibiotic prophylaxis.

The pancreas and spleen 47

AAAC19 21/5/05 10:39 AM Page 47

48 Abdomen and pelvis

20 The posterior abdominal wall

Fig.20.1

The structures of the posterior abdominal wall

Fig.20.2

A section through the right kidney.

The small diagram shows how the renal columns

represent the cortices of adjacent fused lobes

Fig.20.3

The anterior relations of the kidneys

Fig.20.4

The posterior relations of the kidneys

Inferior phrenic artery

Oesophagus

Coeliac artery

Superior mesenteric artery

Iliohypogastric nerve

Ilioinguinal nerve

Inferior mesenteric artery

Femoral nerve

Lateral cutaneous nerve of thigh

Quadratus

lumborum

Psoas major

Genitofemoral

nerve

Median sacral artery

Major calix

Gonadal artery

Outline of pleura

12th rib

Diaphragm

Ureter

Hilar fat

Renal columns

Arcuate

vessels

Interlobar

artery

Pyramid

Minor

calices

Papilla

Spleen

Suprarenal

Stomach

Pancreas

Colon

Liver

Colon

Small

intestine

Duodenum

Small

intestine

Transversus abdominis

Ilio-inguinal nerve

Quadratus lumborum

Psoas major

Subcostal nerve

Transversus

AAAC20 21/5/05 10:39 AM Page 48

The structures of the posterior abdominal wall (Fig. 20.1)

These include:

• Muscles: including psoas major and quadratus lumborum (see

Muscle index, p. 162).

• The abdominal aorta and its branches: see p. 32.

• The inferior vena cava (IVC) and its tributaries: see p. 35.

• The kidneys.

• The ureters.

• The adrenal (suprarenal) glands.

• The lumbar sympathetic trunks and plexuses and the lumbar plexus

(see p. 51).

The kidneys (Fig. 20.2)

• Structure: the kidney has its own ﬁbrous capsule and is surrounded

by perinephric fatwhich, in turn, is enclosed by renal fascia. Each kid-

ney is approximately 10–12 cm long and consists of an outer cortex, an

inner medullaand a pelvis.

The hilum of the kidney is situated medially and transmits from front

to back the: renal vein, renal artery, ureteric pelvis as well as lymphatics

and sympathetic vasomotor nerves.

The renal pelvis divides into two or three major calices and these, in

turn, divide into minor calices which receive urine from the medullary

pyramids by way of the papillae.

• Position: the kidneys lie in the retroperitoneum against the posterior

abdominal wall. The right kidney lies approximately 1cm lower than

the left.

• Relations: See Figs 20.3 and 20.4.

• Blood supply: the renal arteries arise from the aorta at the level of

L2. Together, the renal arteries direct 25% of the cardiac output

towards the kidneys. Each renal artery divides into ﬁve segmental

arteries at the hilum which, in turn, divide sequentially into lobar,

interlobar, arcuate and cortical radial branches. The cortical radial

branches give rise to the afferent arterioles which supply the glomeruli

and go on to become efferent arterioles. The differential pressures

between afferent and efferent arterioles lead to the production of an

ultraﬁltrate which then passes through, and is modiﬁed by, the nephron

to produce urine.

The right renal artery passes behind the IVC. The left renalvein is

long as it courses in front of the aorta to drain into the IVC.

• Lymphatic drainage: to the para-aortic lymph nodes.

The ureter (Fig. 20.1)

The ureter is considered in abdominal, pelvic and intravesical portions.

• Structure: the ureter is approximately 20–30 cm long and courses

from the hilum of the kidney to the bladder. It has a muscular wall and

is lined by transitional epithelium. At operation it can be recognized by

its peristalsis.

• Course: from the renal pelvis at the hilum the course of the ureter can

be summarized as follows:

• It passes along the medial part of psoas major behind, but adherent

to, the peritoneum.

• It then crosses the common iliac bifurcation anterior to the

sacro-iliac joint and courses over the lateral wall of the pelvis to the

ischial spine.

• At the ischial spine the ureter passes forwards and medially to enter

the bladder obliquely. The intravesical portion of the ureter is

approximately 2cm long and its passage through the bladder wall

produces a sphincter-like effect. In the male the ureter is crossed

superﬁcially near its termination by the vas deferens. In the female

the ureter passes above the lateral fornix of the vagina but below

the broad ligament and uterine vessels.

• Blood supply: as the ureter is an abdominal and pelvic structure it

receives a blood supply from multiple sources:

• The upper ureter

areceives direct branches from the aorta, renal

and gonadal arteries.

• The lower ureter

areceives branches of the internal iliac and in-

ferior vesical arteries.

Ureteric stones

Most ureteric calculi arise for unknown reasons, although inadequate

urinary drainage, the presence of infected urine, and hypercalcaemia

are deﬁnite predisposing factors. The presence of an impacted ureteric

stone is characterized by haematuria and agonizing colicky pain

(ureteric colic), which classically radiates from loin to groin. Large

impacted stones can lead to hydronephrosis and/or infection of the

affected kidney and consequently need to be broken up or removed by

interventional or open procedures.

Adrenal (suprarenal) glands (Fig. 20.1)

The adrenal glands comprise an outer cortex and inner medulla. The

cortex is derived from mesoderm and is responsible for the production

of steroid hormones (glucocorticoids, mineralocorticoids and sex

steroids). The medulla is derived from ectoderm (neural crest) and acts

as a part of the autonomic nervous system. It receives sympathetic

preganglionic ﬁbres from the greater splanchnic nerves which

stimulate the medulla to secrete noradrenaline and adrenaline into the

bloodstream.

• Position: the adrenals are small glands which lie in the renal fascia

on the upper poles of the kidneys. The right gland lies behind the right

lobe of the liver and immediately posterolateral to the IVC. The left

adrenal is anteriorly related to the lesser sac and stomach.

• Blood supply: the phrenic, renal arteries and aorta all contribute

branches to the adrenal glands. Venous drainage is on the right to the

IVC and on the left to the left renal vein.

The posterior abdominal wall 49

AAAC20 21/5/05 10:39 AM Page 49

50 Abdomen and pelvis

21 The ner ves of the abdomen

Fig.21.1

The lumbar plexus

Fig.21.2

The sympathetic system in the abdomen and pelvis

Nerves

T12 (subcostal)

Lateral

cutaneous

of thigh

Genitofemoral

Femoral

Obturator

Lumbosacral trunk

Ilioinguinal

Iliohypogastric

Subcostal

Coeliac ganglia

Suprarenal branch

Cut psoas major

Sympathetic trunk

Lumbar sympathetic ganglia

(usually 4)

Superior hypogastric plexus

(presacral nerves)

Pelvic sympathetic ganglia

Grey rami

Grey and white rami

(white rami on first

two lumbar nerves only)

Medial arcuate

ligament

Inferior hypogastric plexus

AAAC21 21/5/05 10:47 AM Page 50

The lumbar plexus (Fig. 21.1)

• The lumbar plexus is formed from the anterior primary rami of L1–4.

The trunks of the plexus lie within the substance of psoas major and,

with the exceptions of the obturator and genitofemoral nerves, emerge

at its lateral border.

• The 12th intercostal nerve is also termed the subcostal nerveas it has

no intercostal space but, instead, runs below the rib in the neurovascu-

lar plane to supply the abdominal wall.

• The iliohypogastric nerve is the main trunk of the 1st lumbar nerve. It

supplies the skin of the upper buttock, by way of a lateral cutaneous

branch, and terminates by piercing the external oblique above the

superﬁcial inguinal ring where it supplies the overlying skin of the

mons pubis. The ilioinguinal nerveis the collateral branch of the iliohy-

pogastric. The ilioinguinal runs in the neurovascular plane of the

abdominal wall to emerge through the superﬁcial inguinal ring to pro-

vide a cutaneous supply to the skin of the medial thigh, the root of the

penis and anterior one third of the scrotum (or labium majus in the

female).

• The genitofemoral nerve (L1,2) emerges from the anterior surface of

psoas major. It courses inferiorly and divides into: a genital component

that enters the spermatic cord and supplies the cremaster (in the male),

and a femoral component that supplies the skin of the thigh overlying

the femoral triangle.

• The lateral cutaneous nerve of the thigh (L2,3), having emerged

from the lateral border of psoas major, encircles the iliac fossa to pass

under the inguinal ligament (p. 99).

• The femoral nerve (L2–4, posterior division): see p. 99.

• The obturator nerve (L2–4, anterior division): see p. 99.

• A large part of L4 joins with L5 to contribute to the sacral plexus as

the lumbosacral trunk.

Lumbar sympathetic chain (Fig. 21.2)

• Sympathetic supply: the lumbar sympathetic chain is a continuation

of the thoracic sympathetic chain as it passes under the medial arcuate

ligament of the diaphragm. The chain passes anterior to the lumbar ver-

tebral bodies and usually carries four ganglia which send grey rami

communicans to the lumbar spinal nerves. The upper two ganglia

receive white rami from L1 and L2.

The lumbar sympathetic chain, the splanchnic nerves and the vagus

contribute sympathetic and parasympathetic branches to plexuses

(coeliac, superior mesenteric, renal and inferior mesenteric) around the

abdominal aorta. In addition, other branches continue inferiorly to form

the superior hypogastric plexus (presacral nerves) from where they

branch into right and left inferior hypogastric plexuses.The latter also

receive a parasympathetic supply from the pelvic splanchnic nerves. The

branches from the inferior hypogastric plexuses are distributed to the

pelvic viscera along the course and branches of the internal iliac artery.

The coeliac gangliaare prominent and lie around the origins of the

coeliac and superior mesenteric arteries.

• Parasympathetic supply: to the pelvic viscera arises from the anter-

ior primary rami of S2,3,4

athe pelvic splanchnic nerves. The latter

parasympathetic supply reaches proximally as far as the junction

between the hindgut and midgut on the transverse colon.

Lumbar sympathectomy

This procedure is performed in cases of severe peripheral vascular dis-

ease of the lower limbs where vascular reconstructive surgery is not

possible and skin necrosis is imminent. The operation involves excision

of the 2nd to 4th lumbar ganglia with the intermediate chain.

The nerves of the abdomen 51

AAAC21 21/5/05 10:47 AM Page 51

52 Abdomen and pelvis

22 Surface anatomy of the abdomen

Transpyloric plane

Costal margin

Vertical line

Subcostal plane

Level of umbilicus

Transtubercular plane

(a)

(b)

Pubic tubercle

Conjoint

tendon

Inferior

epigastric

artery

Deep

ring

Superficial

ring

External oblique

aponeurosis

Spermatic cord

External spermatic fascia

Internal spermatic fascia

Internal oblique

Transversus

Fig.22.1

The nine regions

of the abdomen

Fig.22.2

McBurney's point and some

of the structures that may be

palpated in the abdomen

Fig.22.3

A horizontal section through the inguinal canal. Diagrammatic.

(a) and (b) show the sites of indirect and direct herniae respectively

Cremasteric fascia and muscle

Lower end of rectus abdominus

Transversalis fascia

Peritoneum

Linea alba

Epigastrium

Umbilical

Suprapubic

Hypochondrium

Lumbar

Iliac fossa

Liver, lower edge

(sometimes)

Sigmoid colon

(sometimes)

Linea semilunaris

(lateral border of rectus)

Spleen, anterior notched

margin (when grossly enlarged)

Gall bladder

(when distended)

Lower pole of right

kidney (sometimes)

McBurney's point

Inguinal ligament

Deep inguinal ring

and inferior

epigastric artery

AAAC22 21/5/05 10:47 AM Page 52

Vertebral levels (Fig. 22.1)

(In each case the lower border is referred to.)

• T9: xiphoid process.

• L1: the transpyloric plane (of Addison). This horizontal plane passes

approximately through the tip of the 9th costal cartilage, the pylorus,

pancreatic neck, duodenojejunal ﬂexure, the gall-bladder fundus and

the hila of the kidneys. This plane also corresponds to the level at which

the spinal cord terminates and the lateral edge of rectus abdominis

crosses the costal margin.

• L2: the subcostal plane. This plane corresponds to a line joining the

lowest points of the thoracic cageathe lower margin of the 10th rib

laterally.

• L3: the level of the umbilicus (in a young slim person).

• L4: the transtubercular plane. This corresponds to a line which joins

the tubercles of the iliac crests.

Lines of orientation

Vertical lines: these are imaginary and most often used with the sub-

costal and intertubercular planes, for purposes of description, to subdi-

vide the abdomen into nine regions (Fig. 22.1). They pass vertically, on

either side, through the point halfway between the anterior superior

iliac spine and the pubic tubercle. More commonly used, for descrip-

tion of pain location, are quadrants. The latter are imaginary lines aris-

ing by the bisection of the umbilicus by vertical and horizontal lines.

Surface markings of the abdominal wall

• The costal margin (Fig. 22.1) is the inferior margin of the thoracic

cage. It includes the costal cartilages anteriorly, the 7th–10th ribs later-

ally and the cartilages of the 11th and 12th ribs posteriorly.

• The symphysis pubis is an easily palpable secondary cartilaginous

joint which lies between the pubic bones in the midline. The pubic

tubercle is an important landmark and is identiﬁable on the superior

surface of the pubis.

• The inguinal ligament (Figs 11.1 and 22.2) is attached laterally to the

anterior superior iliac spine and medially to the pubic tubercle.

• The superﬁcial inguinal ring (see Fig. 11.1) is a triangular-shaped

defect in the external oblique aponeurosis. It is situated above and

medial to the pubic tubercle.

• The spermatic cord can be felt passing medial to the pubic tubercle

and descending into the scrotum.

• The deep inguinal ring (Fig. 22.3) lies halfway along a line from the

anterior superior iliac spine to the pubic tubercle.

• The linea alba (see Fig. 11.1) is formed by the fusion of the aponeu-

roses of the muscles of the anterior abdominal wall. It extends as a de-

pression in the midline from the xiphoid process to the symphysis pubis.

• The linea semilunaris is the lateral edge of the rectus abdominis

muscle. It crosses the costal margin at the tip of the 9th costal cartilage.

Inguinal herniae (Figs 22.3 and 52.1)

• Indirect inguinal herniae: arise as a result of persistence of the pro-

cessus vaginalis of the embryo. Abdominal contents bulge through the

deep inguinal ring, into the canal, and eventually into the scrotum. This

hernia can be controlled by digital pressure over the deep ring.

• Direct inguinal herniae: arise as a result of weakness in the poster-

ior wall of the inguinal canal. This hernia cannot be controlled by

digital pressure over the deep ring and only rarely does the hernia pass

into the scrotum.

The clinical distinction between direct and indirect inguinal hernias

can be difﬁcult. At operation, however, the relation of the hernial neck

to the inferior epigastric artery deﬁnes the hernia type, i.e. the neck of

the sac of an indirect hernia lies lateral to the artery whereas that of a

direct type always lies medial to it.

Surface markings of the abdominal viscera (Fig. 22.2)

• Liver: the lower border of the liver is usually just palpable on deep

inspiration in slim individuals. The upper border follows the undersur-

face of the diaphragm and reaches a level just below the nipple on each

side.

• Spleen: this organ lies below the left hemidiaphragm deep to the 9th,

10th and 11th ribs posteriorly. The anterior notch reaches the mid-

axillary line anteriorly.

• Gall-bladder: the fundus of the gall-bladder lies in the transpyloric

plane (L1). The surface marking corresponds to a point where the lat-

eral border of rectus abdominis (linea semilunaris) crosses the costal

margin.

• Pancreas: the pancreatic neck lies on the level of the transpyloric

plane (L1). The pancreatic head lies to the right and below the neck

whereas the body and tail pass upwards and to the left.

• Aorta: the aorta bifurcates to the left of the midline at the level of L4.

• Kidneys: the kidney hila lie on the level of the transpyloric plane

(L1). The lower pole of the right kidney usually extends 3cm below the

level of the left and is often palpable in slim subjects.

• Appendix: McBurney’s point represents the surface marking for the

base of the appendix. This point lies one third of the way along a line

joining the anterior superior iliac spine and the umbilicus. McBurney’s

point is important surgically as it represents the usual site of maximal

tenderness in appendicitis and also serves as the central point for the

incision made when performing an appendicectomy.

• Bladder: in adults the bladder is a pelvic organ and can be palpated

above the symphysis pubis only when full or enlarged.

Surface anatomy of the abdomen 53

AAAC22 21/5/05 10:47 AM Page 53

54 Abdomen and pelvis

The pelvis Icthe bony and ligamentous pelvis

Iliac crest

Anterior gluteal line

Posterior gluteal line

Greater sciatic notch

Lesser sciatic notch

Iliac fossa

Auricular

surface

Iliopectineal

line

Pubic

symphysis

Pubic

tubercle

Spine of ischium

Ischial tuberosity

Ramus of ischium

Inferior ramus

Body of pubis

Pubic crest

Acetabulum

Anterior inferior

iliac spine

Anterior superior

iliac spine

Inferior gluteal line

Pubic tubercle

Obturator foramen

Transverse tubercle

Auricular surface

Posterior sacral

foramen

Posterior superior

iliac spine

Fig.23.1

The lateral surface of the left hip bone

Fig.23.3

The posterior surface of the sacrum

Fig.23.4

The sacrospinous and sacrotuberous ligaments resist

rotation of the sacrum due to the body weight

Fig.23.5

The male pelvic floor from above.

The blue line represents the origin

of levator ani from the obturator

fascia

Fig.23.2

The medial surface of the left hip bone

Sacral hiatus

Body weight

Greater sciatic foramen

Articular tubercle

Ala

Superior articular

facet

Spinous tubercle

Lesser sciatic foramen

Sacrospinous ligament

False

pelvis

Pelvic brim

True pelvis

Sacrotuberous ligament

Perineal body

Prostate

Obturator fascia

Obturator internus

Levator prostatae

Piriformis

Sacral nerves

Spine of ischium

Puborectalis

Anterior edge

of levator ani

Coccygeus

Recto-anal junction

Ischiococcygeus

AAAC23 21/5/05 10:46 AM Page 54

The pelvis is bounded posteriorly by the sacrum and coccyx and antero-

laterally by the innominate bones.

Os innominatum (hip bone) (Figs 23.1 and 23.2)

This bone comprises three component parts, the: ilium, ischium and

pubis. By adulthood the constituent bones have fused together at the

acetabulum. Posteriorly each hip bone articulates with the sacrum at the

sacro-iliac joint(a synovial joint).

• Ilium: the iliac crest forms the upper border of the bone. It runs back-

wards from the anterior superior iliac spine to the posterior superior

iliac spine. Below each of these bony landmarks are the corresponding

inferior spines. The outer surface of the ilium is termed the gluteal sur-

face as it is where the gluteal muscles are attached. The inferior,anter-

ior and posterior gluteal lines demarcate the bony attachments of the

glutei. The inner surface of the ilium is smooth and hollowed out to

form the iliac fossa. It gives attachment to the iliacus muscle. The

auricular surface of the ilium articulates with the sacrum at the sacro-

iliac joints(synovial joints). Posterior, interosseous andanterior sacro-

iliac ligaments strengthen the sacro-iliac joints. The iliopectineal line

courses anteriorly on the inner surface of the ilium from the auricular

surface to the pubis. It forms the lateral margin of thepelvic brim (see

below).

• Ischium: comprises a spine on its posterior part which demarcates

the greater (above) and lesser sciatic (below) notches. The ischial

tuberosity is a thickening on the lower part of the body of the ischium

which bears weight in the sitting position. The ischial ramus projects

forwards from the tuberosity to meet and fuse with the inferior pubic

ramus.

• Pubis: comprises a body and superior and inferior pubic rami. It

articulates with the pubic bone of the other side at the symphysis pubis

(a secondary cartilaginous joint). The superior surface of the body

bears the pubic crestand the pubic tubercle (Fig. 23.1).

The obturator foramenis a large opening bounded by the rami of the

pubis and ischium.

The sacrum and coccyx (Fig. 23.3)

• The sacrum comprises ﬁve fused vertebrae. The anterior and lateral

aspects of the sacrum are termed the central andlateral masses, respect-

ively. The upper anterior part is termed the sacral promontory. Four

anterior sacral foramina on each side transmit the upper four sacral

anterior primary rami. Posteriorly, the fused pedicles and laminae form

the sacral canal representing a continuation of the vertebral canal.

Inferiorly, the canal terminates at the sacral hiatus. Sacral cornua

bound the hiatus inferiorly on either side. The subarachnoid space ter-

minates at the level of S2. The sacrum is tilted anteriorly to form the

lumbosacral anglewith the lumbar vertebra.

• The coccyx articulates superiorly with the sacrum. It comprises

between three and ﬁve fused rudimentary vertebrae.

The obturator membrane

The obturator membrane is a sheet of ﬁbrous tissue which covers the

obturator foramen with the exception of a small area for the passage of

the obturator nerve and vessels which traverse the canal to pass from

the pelvis to gain access to the thigh.

The pelvic cavity

The pelvic brim(also termed the pelvic inlet) separates the pelvis into

the false pelvis(above) and the true pelvis (below). The brim is formed

by the sacral promontory behind, the iliopectineal lines laterally and the

symphysis pubis anteriorly. The pelvic outletis bounded by the coccyx

behind, the ischial tuberosities laterally and thepubic arch anteriorly.

The true pelvis (pelvic cavity) lies between the inlet and outlet. The

false pelvis is best considered as part of the abdominal cavity.

The ligaments of the pelvis (Fig. 23.4)

These include the:

• Sacrotuberous ligament: extends from the lateral part of the sacrum

and coccyx to the ischial tuberosity.

• Sacrospinous ligament: extends from the lateral part of the sacrum

and coccyx to the ischial spine.

The above ligaments, together with the sacro-iliac ligaments, bind

the sacrum and coccyx to the os and prevent excessive movement at the

sacro-iliac joints. In addition, these ligaments create the greater and

lesser sciatic foraminawith the greater and lesser sciatic notches.

The pelvic ﬂoor (Fig. 23.5)

The pelvic ﬂoor muscles: support the viscera; produce a sphincter

action on the rectum and vagina and help to produce increases in intra-

abdominal pressure during straining. The rectum, urethra and vagina

(in the female) traverse the pelvic ﬂoor to gain access to the exterior.

The levator ani and coccygeus muscles form the pelvic ﬂoor, while piri-

formis covers the front of the sacrum.

• Levator ani: arises from the posterior aspect of the pubis, the fascia

overlying obturator internus on the side wall of the pelvis and the

ischial spine. From this broad origin ﬁbres sweep backwards towards

the midline as follows:

• Anterior ﬁbres (sphincter vaginae or levator prostatae)athese

ﬁbres surround the vagina in the female (prostate in the male) and

insert into the perineal body. The latter structure is a ﬁbromuscular

node which lies anterior to the anal canal.

• Intermediate ﬁbres ( puborectalis)athese ﬁbres surround the

anorectal junction and also insert into the deep part of the anal

sphincter. They provide an important voluntary sphincter action at

the anorectal junction.

• Posterior ﬁbres (iliococcygeus)athese ﬁbres insert into the lateral

aspect of the coccyx and a median ﬁbrous raphe (the anococcygeal

body).

• Coccygeus: arises from the ischial spine and inserts into the lower

sacrum and coccyx.

Sex differences in the pelvis

The female pelvis differs from that of the male for the purpose of child-

bearing. The major sex differences include:

1 The pelvic inlet is oval in the female. In the male the sacral promon-

tory is prominent, producing a heart-shaped inlet.

2 The pelvic outlet is wider in females as the ischial tuberosities are

everted.

3 The pelvic cavity is more spacious in the female than in the male.

4 The false pelvis is shallow in the female.

5 The pubic arch (the angle between the inferior pubic rami) is wider

and more rounded in the female when compared with that of the male.

The pelvis Ibthe bony and ligamentous pelvis 55

AAAC23 21/5/05 10:46 AM Page 55

56 Abdomen and pelvis

The pelvis IIcthe contents of the pelvis

External

iliac vessels

Round

ligament

Ligament

of the ovary

Round ligament

Uterine artery

Cut edge of

broad ligament

Ureter Transverse

cervical ligament

Internal iliac

vessels

Uterine tube

Uterosacral

ligament

Pubocervical

ligament

Bladder

Rectum

Cervix

Endopelvic

fascia

Cardinal

ligaments

Infundibulopelvic

ligament

Ureter

Fimbriated end

of tube

Ovary

Internal pudendal artery

Attachment of levator ani

Mesovarium

Obturator artery

Ductus deferens

Inferior epigastric artery

External iliac artery

Deep circumflex

iliac artery

Ureter

Obliterated umbilical artery

Inferior vesical and middle

rectal arteries

Tendon of obturator internus

Inferior gluteal artery

Superior gluteal artery

Obturator nerve

Iliolumbar artery

Lateral sacral artery

Fig. 24.2

The broad ligament cut off close to the uterus

Fig. 24.1

The ligaments of the uterus

Fig. 24.3

The pelvic arteries in the male

AAAC24 21/5/05 10:46 AM Page 56

Pelvic fascia (Fig. 24.1)

The pelvic fasciais the term given to the connective tissue that lines the

pelvis covering levator ani and obturator internus. It is continuous with

the fascial layers of the abdominal wall above and the perineum below.

Endopelvic fasciais the term given to the loose connective tissue that

covers the pelvic viscera. The endopelvic fascia is condensed into fas-

cial ligaments which act as supports for the cervix and vagina. These

ligaments include the:

• Cardinal (Mackenrodt’s) ligaments: pass laterally from the cervix

and upper vagina to the pelvic side walls.

• Utero-sacral ligaments: pass backwards from the cervix and va-

ginal fornices to the fascia overlying the sacro-iliac joints.

• Pubocervical ligaments: extend anteriorly from the cardinal liga-

ments to the pubis (puboprostatic in the male).

• Pubovesical ligaments: from the back of the symphysis pubis to the

bladder neck.

The broad and round ligaments (Fig. 24.2)

• Broad ligament: is a double fold of peritoneum which hangs

between the lateral aspect of the uterus and the pelvic side walls. The

ureter passes forwards under this ligament, but above and lateral to the

lateral fornix of the vagina, to gain access to the bladder. The broad liga-

ment contains the following structures:

• Fallopian tube.

• Ovary.

• Ovarian ligament.

• Round ligament (see below).

• Uterine and ovarian vessels.

• Nerves and lymphatics.

• Round ligament: is a cord-like ﬁbromuscular structure which is the

female equivalent of the gubernaculum in the male. It passes from the

lateral angle of the uterus to the labium majus by coursing in the broad

ligament and then through the inguinal canal (p. 30).

Arteries of the pelvis (Fig. 24.3)

• Common iliac arteries: arise from the aortic bifurcation to the left of

the midline at the level of the umbilicus. These arteries, in turn, bifur-

cate into external and internal iliac branches anterior to the sacro-iliac

joints on either side.

• External iliac artery: courses from its origin (described above) to

become the femoral artery as it passes under the inguinal ligament at

the mid-inguinal point. The external iliac artery gives rise to branches

which supply the anterior abdominal wall. These include the: deep cir-

cumﬂex iliac artery and inferior epigastric artery. The latter branch

gains access to the rectus sheath, which it supplies, and eventually

anastomoses with the superior epigastric artery.

• Internal iliac artery: courses from its origin (described above)

to divide into anterior and posterior trunks at the level of the greater

sciatic foramen.

Branches of the anterior trunk

• Obturator artery: passes with the obturator nerve through the obtur-

ator canal to enter the thigh.

• Umbilical artery: although the distal part is obliterated the proximal

part is patent and gives rise to the superior vesical artery which con-

tributes a supply to the bladder.

• Inferior vesical artery: as well as contributing a supply to the blad-

der it also gives off a branch to the vas deferens(in the male).

• Middle rectal artery: anastomoses with the superior and inferior

rectal arteries to supply the rectum.

• Internal pudendal artery: is the predominant supply to the per-

ineum. It exits the pelvis brieﬂy through the greater sciatic foramen but

then re-enters below piriformis through the lesser sciatic foramen to

enter the pudendal canal together with the pudendal nerve.

• Uterine artery: passes medially on the pelvic ﬂoor and then over the

ureter and lateral fornix of the vagina to ascend the lateral aspect of the

uterus between the layers of the broad ligament.

• Inferior gluteal artery: passes out of the pelvis through the greater

sciatic foramen to the gluteal region which it supplies.

• Vaginal artery.

Branches of the posterior trunk

• Superior gluteal artery: contributes a supply to the gluteal muscles.

It leaves the pelvis through the greater sciatic foramen.

• Ilio-lumbar artery.

• Lateral sacral artery.

Veins of the pelvis

The right and left common iliac veins join to form the inferior vena

cava behind the right common iliac artery but anterolateral to the body

of L5. The overall arrangement of pelvic venous drainage reciprocates

that of the arterial supply.

Nerves of the pelvis

Sacral plexus (see p. 100).

The pelvis IIbthe contents of the pelvis 57

AAAC24 21/5/05 10:46 AM Page 57

58 Abdomen and pelvis

25 The perineum

Fig.25.3

The testis and epididymis

Fig.25.2

The female perineum

Fig.25.1

The male perineum

Crus clitoris

Glans clitoris

Pampiniform

plexus

Epididymis

Testis

Testicular

artery

Vas deferens

Tunica

vaginalis

Bulbospongiosus

Muscles

Ischiocavernosus

Superficial transverse

perineal muscle

External anal sphincter

Levator ani

Gluteus maximus

Urethra

Bulb

Vagina

Bartholin's gland

Perineal membrane

Perineal body

Ischial tuberosity

Bulbospongiosus

Muscles

Ischiocavernosus

Superficial transverse

perineal muscle

External sphincter ani

Levator ani

Gluteus maximus

Dorsal vein

Corpus cavernosum

Corpus spongiosum

with urethra

Penile

Crus

Bulb

Perineal membrane

Perineal body

AAAC25 21/5/05 10:46 AM Page 58

The perineum lies below the pelvic diaphragm. It forms a diamond-

shaped area when viewed from below that can be divided into an anter-

ior urogenital region and a posterior anal region by a line joining the

ischial tuberosities horizontally.

Anal region (Figs 25.1 and 17.2)

The anal region contains the anal canal and ischiorectal fossae.

• Anal canal: is described earlier (p. 43).

• Anal sphincter: comprises external and internal sphincter compon-

ents. The internal anal sphincteris a continuation of the inner circular

smooth muscle of the rectum. The external anal sphincteris a skeletal

muscular tube which, at its rectal end, blends with puborectalis to form

an area of palpable thickening termed theanorectal ring. The compet-

ence of the latter is fundamental to anal continence.

• Ischiorectal fossae: lie on either side of the anal canal. The medial

and lateral walls of the ischiorectal fossa are the levator ani and anal

canal and the obturator internus, respectively. The fossae are ﬁlled with

fat. The anococcygeal body separates the fossae posteriorly; however,

infection in one fossa can spread anteriorly to the contralateral fossa

forming a horseshoe abscess. The pudendal (Alcock’s) canalis a sheath

in the lateral wall of the ischiorectal fossa. It conveys the pudendal

nerve and internal pudendal vessels from the lesser sciatic notch to the

deep perineal pouch (see below). The inferior rectal branches of the

pudendal nerve and internal pudendal vessels course transversely

across the fossa to reach the anus.

Urogenital region

The urogenital region is triangular in shape. The perineal membraneis

a strong fascial layer that is attached to the sides of the urogenital tri-

angle. In the male it is pierced by the urethra and, in females, by the

urethra and vagina.

(a) In the female (Fig. 25.2)

• Vulva: is the term given to the female external genitalia. The mons

pubis is the fatty protuberance overlying the pubic symphysis and

pubic bones. The labia majora are fatty hair-bearing lips that extend

posteriorly from the mons. The labia minora lie internal to the labia

majora and unite posteriorly at the fourchette. Anteriorly, the labia

minora form the prepuce and split to enclose the clitoris. The clitoris

corresponds to the penis in the male. It has a similar structure in that it is

made up of three masses of erectile tissue: the bulb (corresponding to

the penile bulb) and right and left crura covered by similar but smaller

muscles than those in the male. As in the male, these form the contents

of the superﬁcial perineal pouch. The deep perineal pouch, however,

contains the vagina as well as part of the urethra and sphincter urethrae

and internal pudendal vessels. The vestibuleis the area enclosed by the

labia minora and contains the urethral and vaginal oriﬁces. Deep to the

posterior aspect of the labia majoris lie Bartholin’s glandsaa pair of

mucus-secreting glands that drain anteriorly. They are not palpable in

health but can become grossly inﬂamed when infected.

• Urethra: is short in the female (3–4 cm). This factor contributes

towards the predisposition to urinary tract infection due to upward

spread of bowel organisms. The urethra extends from the bladder neck

to the external meatus. The meatus lies between the clitoris and vagina.

• Vagina: measures approximately 8–12 cm in length. It is a muscular

tube that passes upwards and backwards from the vaginal oriﬁce. The

cervix projects into the upper anterior aspect of the vagina creating

fornices anteriorly, posteriorly and laterally. Lymph from the upper

vagina drains into the internal and external iliac nodes. Lymph from the

lower vagina drains to the superﬁcial inguinal nodes. The blood supply

to the vagina is from the vaginal artery (branch of the internal iliac

artery) and the vaginal branch of the uterine artery.

(b) In the male (Fig. 25.1)

The external urethral sphincter (striated muscle) lies deep to the per-

ineal membrane within a fascial capsule termed the deep perineal

pouch. In addition to the sphincter, two glands of Cowper are also

contained within the deep pouch. The ducts from these glands pass

forwards to drain into the bulbous urethra. Inferior to the perineal mem-

brane is the superﬁcial perineal pouchwhich contains the:

• Superﬁcial transverse perineal muscles: run from the perineal

body to the ischial ramus.

• Bulbo-spongiosus muscle: covers the corpus spongiosum. The lat-

ter structure covers the spongy urethra.

• Ischio-cavernosus muscle: arises on each side from the ischial

ramus to cover the corpus cavernosum. It is the engorgement of venous

sinuses within these cavernosa that generate and maintain an erection.

Hence, the penile root comprises a well-vascularized bulb and two

crura which are supplied by branches of the internal pudendal artery.

The erectile penile tissue is enclosed within a tubular fascial sheath. At

the distal end of the penis the corpus spongiosum expands to form the

glans penis. On the tip of the glans the urethra opens as the external

urethralmeatus. The foreskin is attached to the glans below the meatus

by a fold of skinathe frenulum.

The scrotum

The skin of the scrotum is thin, rugose and contains many sebaceous

glands. A longitudinal median rapheis visible in the midline. Beneath the

skin lies a thin layer of involuntary dartosmuscle. The terminal spermatic

cords, the testes and their epididymes are contained within the scrotum.

Testis and epididymis (Fig. 25.3)

The testes are responsible for spermatogenesis. Their descent to an extra-

abdominal position favours optimal spermatogenesis as the ambient

scrotal temperature is approximately 3°C lower than body temperature.

• Structure: the testis is divided internally by a series of septa into

approximately 200 lobules. Each lobule contains 1–3 seminiferous

tubules which anastomose into a plexus termed the rete testis. Each

tubule is coiled when in situ, but when extended measures approxim-

ately 60cm. Efferent ducts connect the rete testis to the epididymal

head. They serve to transmit sperm from the testicle to the epididymis.

• The tunica vaginalis, derived from the peritoneum, is a double

covering into which the testis is invaginated.

• The tunica albuginea is a tough ﬁbrous capsule that covers the testis.

• The epididymis lies along the posterolateral and superior borders of

the testicle. The tunica vaginalis covers the epididymis with the

exception of the posterior border.

• The upper poles of both the testis and epididymis bear an appendix

testis and appendix epididymis (hydatid of Morgagni), respectively.

• Blood supply: is from the testicular artery (a branch of the abdom-

inal aorta, p. 32). Venous drainage from the testicle is to the pampini-

form plexus of veins. The latter plexus lies within the spermatic cord

but coalesces to form a single vein at the internal ring. The left testicu-

lar vein drains to the left renal vein whereas the right testicular vein

drains directly to the inferior vena cava.

• Lymphatic drainage: is to the para-aortic lymph nodes.

• Nerve supply: is from T10 sympathetic ﬁbres via the renal and aortic

plexuses.

The perineum 59

AAAC25 21/5/05 10:46 AM Page 59

60 Abdomen and pelvis

26 The pelvic viscera

Contents of the pelvic cavity (see Fig. 24.1)

• Sigmoid colon: see p. 43.

• Rectum: see p. 43.

• Ureters: see p. 49.

• Bladder (Fig. 26.2): see below.

Bladder

In adults the bladder is a pelvic organ. It lies behind the pubis and is

covered superiorly by peritoneum. It acts as a receptacle for urine and

has a capacity of approximately 500mL.

• Structure: the bladder is pyramidal in shape. The apex of the pyra-

mid points forwards and from it a ﬁbrous cord, the urachus, passes

upwards to the umbilicus as the median umbilical ligament. The base

(posterior surface) is triangular. In the male, the seminal vesicles lie on

the outer posterior surface of the bladder and are separated by the vas

deferens. The rectum lies behind. In the female, the vagina intervenes

between the bladder and rectum. The inferolateralsurfaces are related

inferiorly to the pelvic ﬂoor and anteriorly to the retropubic fat pad and

pubic bones. The bladder neck fuses with the prostate in the male

whereas it lies directly on the pelvic fascia in the female. The pelvic

Body

Internal os

Supravaginal cervix

Intravaginal cervix

Cervical canal

Lateral fornix

External os

Vagina

Fallopian tube

Bladder

Spongiose

urethra

Ureter

Vaginal artery

Uterine

artery

Ovarian

artery

Lateral

cornu

Rectovesical

pouch

Cavity

Fundus

Fig.26.3

A vertical section through the uterus and vagina.

Note the relation of the uterine artery to the ureter

Fig.26.1

Sagittal sections through the male and female pelves

Prostate

Ureter

Ductus

deferens

Seminal

vesicle

Urachus

Fig.26.2

The bladder and prostate

Ampulla

Prostate

Urethra

Trigone

Ureter

Sphincter

urethrae

Prostate

Rectum

Uterovesical

pouch

Recto-uterine pouch

Anal canal

Perineal

body

Prostatic

urethra

Membranous

urethra

Suspensory

ligament

Bladder

Urethra

Vagina

Vestibule

Perineal body

Posterior fornix

of vagina

Cervix of uterus

Sphincter ani

externus

Anal canal

AAAC26 21/5/05 10:45 AM Page 60

fascia is thickened in the form of the puboprostatic ligaments (male)

and pubovesical ligaments to hold the bladder neck in position. The

mucous membrane of the bladder is thrown into folds when the bladder

is empty with the exception of the membrane overlying the base

(termed the trigone) which is smooth. The superior angles of the

trigone mark the openings of the ureteric oriﬁces. A muscular eleva-

tion, the interureteric ridge, runs between the ureteric oriﬁces. The

inferior angle of the trigone corresponds to the internal urethral mea-

tus. The muscle coat of the bladder is composed of a triple layer of tra-

beculated smooth muscle known as the detrusor (muscle). The detrusor

is thickened at the bladder neck to form the sphincter vesicae.

• Blood supply: is from the superior and inferior vesical arteries

(branches of the internal iliac artery, p. 57). The vesical veins coalesce

around the bladder to form a plexus that drains into the internal iliac

vein.

• Lymph drainage: is to the para-aortic nodes.

• Nerve supply: motor input to the detrusor muscle is from efferent

parasympathetic ﬁbres from S2–4. Fibres from the same source convey

inhibitory ﬁbres to the internal sphincter so that co-ordinated micturi-

tion can occur. Conversely, sympathetic efferent ﬁbres inhibit the

detrusor and stimulate the sphincter.

The male pelvic organs

The prostate (Fig. 26.2)

In health the prostate is approximately the size of a walnut. It surrounds

the prostatic urethra and lies between the bladder neck and the urogen-

ital diaphragm. The apex of the prostate rests on the external urethral

sphincter of the bladder. It is related anteriorly to the pubic symphysis

but separated from it by extraperitoneal fat in the retropubic space

(cave of Retzius). Posteriorly, the prostate is separated from the rectum

by the fascia of Denonvilliers.

• Structure: the prostate comprises anterior, posterior, middle and lat-

eral lobes. On rectal examination a posterior median groove can be pal-

pated between the lateral lobes. The prostatic lobes contain numerous

glands producing an alkaline secretion which is added to the seminal

ﬂuid at ejaculation. The prostatic glands open into the prostatic sinus.

The ejaculatory ducts, which drain both the seminal vesicles and the

vas, enter the upper part of the prostate and then the prostatic urethra at

the verumontanum.

• Blood supply: is from the inferior vesical artery (branch of the inter-

nal iliac artery, p. 57). A prostatic plexus of veins is situated between

the prostatic capsule and the outer ﬁbrous sheath. The plexus receives

the dorsal vein of the penis and drains into the internal iliac veins.

The vas deferens

The vas deferens conveys sperm from the epididymis to the ejaculatory

duct from which it can be passed to the urethra. The vas arises from the

tail of the epididymis and traverses the inguinal canal to the deep ring,

passes downwards on the lateral wall of the pelvis almost to the ischial

tuberosity and turns medially to reach the base of the bladder where it

joins with the duct of the seminal vesicle to form the ejaculatory duct.

The seminal vesicles (Fig. 26.2)

The seminal vesicles consist of lobulated tubes which lie extraperi-

toneally on the bladder base lateral to the vas deferens.

The urethra (Fig. 26.1)

The male urethra is approximately 20cm long (4 cm in the female). It

is considered in three parts:

• Prostatic urethra (3 cm): bears a longitudinal elevation (urethral

crest) on its posterior wall. On either side of the crest a shallow depres-

sion, theprostatic sinus, marks the drainage point for 15–20 prostatic

ducts. The prostatic utricle is a 5mm blind ending tract which opens

into an eminence in the middle of the crestathe verumontanum. The

ejaculatory ducts open on either side of the utricle.

• Membranous urethra (2 cm): lies in the urogenital diaphragm and

is surrounded by the external urethral sphincter (sphincter urethrae).

• Penile urethra (15 cm): traverses the corpus spongiosum of the

penis (see perineum, p. 59) to the external urethral meatus.

The female pelvic organs

The vagina

See perineum, p. 59.

The uterus and fallopian tubes (Fig. 26.3)

• Structure: the uterus measures approximately 8 cm in length in the

nulliparous female. It comprises a: fundus (part lying above the

entrance of the fallopian tubes), body andcervix. The cervix is sunken

into the anterior wall of the vagina and is consequently divided into

supravaginal and vaginal parts. The internal cavity of the cervix com-

municates with the cavity of the body at the internal os and with the

vagina at the external os. The fallopian tubes lie in the free edges of the

broad ligaments and serve to transmit ova from the ovary to the cornua

of the uterus. They comprise an: infundibulum, ampulla, isthmus and

interstitial part. The uterus is made up of a thick muscular wall

(myometrium) and lined by a mucous membrane (endometrium). The

endometrium undergoes massive cyclical change during menstruation.

• Relations: the uterus and cervix are related to the uterovesical pouch

and superior surface of the bladder anteriorly. The recto-uterine pouch

(of Douglas), which extends down as far as the posterior fornix of the

vagina, is a posterior relation. The broad ligament is the main lateral

relation of the uterus.

• Position: in the majority, the uterus is anteverted, i.e. the axis of the

cervix is bent forward on the axis of the vagina. In some women the

uterus is retroverted.

• Blood supply: is predominantly from the uterine artery (a branch of

the internal iliac artery, p. 57). It runs in the broad ligament and, at the

level of the internal os, crosses the ureter at right angles to reach, and

supply, the uterus before anastomosing with the ovarian artery (a

branch of the abdominal aorta, p. 32).

• Lymph drainage: lymphatics from the fundus accompany the ovar-

ian artery and drain into the para-aortic nodes. Lymphatics from the

body and cervix drain to the internal and external iliac lymph nodes.

The ovary

Each ovary contains a number of primordial follicles which develop in

early fetal life and await full development into ova. In addition to the

production of ova, the ovaries are also responsible for the production of

sex hormones. Each ovary is surrounded by a ﬁbrous capsule, the

tunica albuginea.

• Attachments: the ovary lies next to the pelvic side wall and is

secured in this position by two structures: the broad ligament which

attaches the ovary posteriorly by the mesovarium; and the ovarian liga-

mentwhich secures the ovary to the cornu of the uterus.

• Blood supply: is from the ovarian artery (a branch of the abdominal

aorta). Venous drainage is to the inferior vena cava on the right and to

the left renal vein on the left.

• Lymphatic drainage: is to the para-aortic nodes.

The pelvic viscera 61

AAAC26 21/5/05 10:45 AM Page 61

The clavicle (Fig. 27.1)

• The clavicle is the ﬁrst bone to ossify in the fetus (6 weeks).

• It develops in membrane and not in cartilage.

• It is subcutaneous throughout its length and transmits forces from the

arm to the axial skeleton.

• The medial two-thirds are circular in cross-section and curved con-

vex forwards. The lateral third is ﬂat and curved convex backwards.

• The clavicle articulates medially with the sternum and 1st costal car-

tilage at the sternoclavicular joint. The clavicle is also attached medi-

ally to the 1st rib by strong costoclavicular ligaments and to the

sternum by sternoclavicular ligaments.

62 Upper limb

27 The osteology of the upper limb

Fig.27.1

The upper and lower surfaces of the left clavicle

Fig.27.2

X-ray of a fractured clavicle

Facet for acromion

Medial (sternal) end

Trapezoid line

Tubercle for costo-

clavicular ligament

Conoid tubercule

• The clavicle articulates laterally with the acromion process of the

scapulaathe acromioclavicular joint. The coracoclavicular ligaments

secure the clavicle inferolaterally to the coracoid process of the

scapula. This ligament has two componentsathe conoidand trapezoid

ligamentswhich are attached to the conoid tubercle and trapezoid line

of the clavicle, respectively.

• The clavicle is the most commonly fractured bone in the body. The

weakest point of the bone is the junction of the middle and outer thirds

(Fig. 27.2).

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• The greater and lesser tubercles provide attachment for the rotator

cuffmuscles. The tubercles are separated by the intertubercular sulcus

in which the long head of biceps tendon courses.

• A faint spiral grooveis visible on the posterior aspect of the humeral

shaft traversing obliquely downwards and laterally. Themedial and lat-

eral heads of tricepsoriginate on either side of this groove. The radial

nerve passes between the two heads.

• The ulnar nerve winds forwards in a groove behind the medial

epicondyle.

• At the elbow joint: thetrochlea articulates with the trochlear notch of

the ulna;and the rounded capitulum with the radial head. The medial

border of the trochlea projects inferiorly a little further than the lateral

border. This accounts for thecarrying angle, i.e. the slight lateral angle

made between the arm and forearm when the elbow is extended.

The osteology of the upper limb 63

The scapula (Fig. 27.3)

• The scapula is triangular in shape. It provides an attachment for

numerous muscles.

• The glenoid fossa articulates with the humeral head (gleno-humeral

joint), and the acromion process with the clavicle (acromioclavicular

joint).

The humerus (Fig. 27.4)

• The humeral head consists of one third of a sphere. The rounded head

articulates with the shallowglenoid. This arrangement permits a wide

range of shoulder movement.

• The anatomical neck separates the head from the greater and lesser

tubercles. The surgical neck lies below the anatomical neck between

the upper end of the humerus and shaft. The axillary nerve and cir-

cumﬂex vessels wind around the surgical neck of the humerus. These

are at risk of injury in shoulder dislocations and humeral neck fractures

(see Fig. 34.3).

Fig.27.3

Posterior and anterior views of the left scapula

Fig.27.4

Anterior and posterior views of the left humerus

Acromion

Coracoid process

Superior angle

Medial border

Greater tubercle

Glenoid fossa

Acromion

Spine

Head

Supraspinous

fossa

Infraspinous

fossa

Suprascapular notch

Spinoglenoid notch

Intertubercular

sulcus

Medial

supracondylar

ridge

Medial

epicondyle

Lesser

tubercle

Subscapular fossa

Lateral border

Anatomical

neck

Surgical

neck

Deltoid

tuberosity

Spiral

groove

Olecranon

fossa

Trochlea

Capitulum

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The radius and ulna (Fig. 27.5)

• Both the radius and ulna have interosseous, anterior and posterior

borders.

• The biceps tendon inserts into the roughened posterior part of the

radial tuberosity. The anterior part of the tuberosity is smooth where it

is covered by a bursa.

•Theradialhead is at its proximal end whilst the ulnar head is at its

distal end.

• The lower end of the radius articulates with the scaphoid and lunate

carpal bones at the wrist joint. The distal ulna does not participate

directly in the wrist joint.

• The dorsal tubercle (of Lister) is located on the posterior surface of

the distal radius.

64 Upper limb

• In pronation/supination movements the radial head rotates in the

radial notch of the ulna and the radial shaft pivots around the relatively

ﬁxed ulna (connected by the interosseous ligament). The distal radius

rotates around the head of the ulna.

A Colles fracture is a common injury occurring at the wrist in the

elderly and usually osteoporotic population. It classically follows a fall

on the outstretched hand. The fracture line is usually about 2.5 cm

proximal to the wrist and the distal fragment displaces posteriorly (din-

nerfork deformity when viewed from the side) and radially. Some

degree of shortening often occurs due to impaction of the component

parts(Fig. 27.6).

Fig.27.6

X-ray of a fracture of the lower end

of the radius (Colles' fracture)

Radial styloid

Fig.27.5

The left radius and ulna in (a) supination and (b) pronation

Supinator

crest

Trochlear

notch

Olecranon

Head

of ulna

Head

radius

Coronoid

process

Ulna styloid

Radial

tuberosity

Tuberosity

of the

ulna

Interosseous

borders

Dorsal

tubercle

Attachment

pronator

teres

AAAC27 21/5/05 10:45 AM Page 64

The hand (Fig. 27.7)

The carpal bones are arranged into two rows. The palmar aspect of the

carpus is concave. This is brought about by the shapes of the con-

stituent bones and the ﬂexor retinaculumbridging the bones anteriorly

to form the carpal tunnel (see Fig. 38.1).

The scaphoid may be fractured through a fall on the outstretched

hand. This injury is common in young adults and must be suspected

clinically when tenderness is elicited by deep palpation in the anatomi-

cal snuffbox. Radiographic changes are often not apparent and, if

effective treatment is not implemented, permanent wrist weakness and

secondary osteoarthritis may follow. The blood supply to the scaphoid

enters via its proximal and distal ends. However, in as many as one

third of cases the blood supply enters only from the distal end. Under

these circumstances the proximal scaphoid fragment may be deprived

of arterial supply and undergo avascular necrosis.

The osteology of the upper limb 65

Fig.27.7

The skeleton of the left hand, holding a cross-section through the carpal tunne

Triquetral

Lunate

Tubercle of scaphoid

Hook of hamate

Pisiform

Trapezium

Pisiform

Triquetral

Flexor retinaculum

Scaphoid

Lunate

Trapezoid

Capitate

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