Clinical Anatomy
Applied anatomy for students and junior doctors
Harold Ellis
ELEVENTH EDITION
Clinical Anatomy
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To my wife and late parents
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Clinical Anatomy
A revision and applied anatomy
for clinical students
HAROLD◊ELLIS
CBE, MA, DM, MCh, FRCS, FRCP, FRCOG, FACS (Hon)
Clinical Anatomist, Guy’s, King’s and
St Thomas’ School of Biomedical Sciences;
Emeritus Professor of Surgery, Charing Cross
and Westminster Medical School, London;
Formerly Examiner in Anatomy, Primary FRCS (Eng)
ELEVENTH EDITION
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© 2006 Harold Ellis
Published by Blackwell Publishing Ltd
Blackwell Publishing, Inc., 350 Main Street, Malden, Massachusetts 02148-5020, USA
Blackwell Publishing Ltd, 9600 Garsington Road, Oxford OX4 2DQ, UK
Blackwell Publishing Asia Pty Ltd, 550 Swanston Street, Carlton, Victoria 3053,
Australia
The right of the Author to be identified as the Author of this Work has been asserted
in accordance with the Copyright, Designs and Patents Act 1988.
All rights reserved. No part of this publication may be reproduced, stored in a
retrieval system, or transmitted, in any form or by any means, electronic,
mechanical, photocopying, recording or otherwise, except as permitted by the UK
Copyright, Designs and Patents Act 1988, without the prior permission of the
publisher.
First published 1960
Seventh edition 1983
Second edition 1962
Revised reprint 1986
Reprinted 1963
Eighth edition 1992
Third edition 1966
Ninth edition 1992
Fourth edition 1969
Reprinted 2000
Fifth edition 1971
Tenth edition 2002
Sixth edition 1977
Reprinted 2003, 2004
Reprinted 1978, 1980
Greek edition 1969
Eleventh edition 2006
1 2006
Library of Congress Cataloging-in-Publication Data
Data available
ISBN-13: 978-1-4051-3804-8
ISBN-10: 1-4051-3804-1
A catalogue record for this title is available from the British Library
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accept responsibility or legal liability for any errors in the text or for the misuse or
misapplication of material in this book.
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Contents
Preface, xiii
Acknowledgements, xiv
Part 1:◊The Thorax
Surface anatomy and surface markings, 3
◊◊Surface markings of the more important thoracic contents, 3
The thoracic cage, 7
◊◊The thoracic vertebrae, 7
◊◊The ribs, 7
◊◊The costal cartilages, 10
◊◊The sternum, 11
◊◊The intercostal spaces, 11
◊◊The diaphragm, 14
◊◊The pleurae, 18
The lower respiratory tract, 19
◊◊The trachea, 19
◊◊The bronchi, 23
◊◊The lungs, 23
The mediastinum, 28
◊◊The pericardium, 28
◊◊The heart, 29
◊◊The superior mediastinum, 42
◊◊The oesophagus, 42
◊◊The thoracic duct, 45
◊◊The thoracic sympathetic trunk, 47
On the examination of a chest radiograph, 49
◊◊Radiographic appearance of the heart, 50
Part 2:◊The Abdomen and Pelvis
Surface anatomy and surface markings, 55
◊◊Vertebral levels, 55
◊◊Surface markings, 55
The fasciae and muscles of the abdominal wall, 58
◊◊Fasciae of the abdominal wall, 58
◊◊The muscles of the anterior abdominal wall, 58
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◊◊The anatomy of abdominal incisions, 61
◊◊The inguinal canal, 63
Peritoneal cavity, 65
◊◊Intraperitoneal fossae, 68
◊◊The subphrenic spaces, 69
The gastrointestinal tract, 70
◊◊The stomach, 70
◊◊The duodenum, 75
◊◊Small intestine, 77
◊◊Large intestine, 78
◊◊The appendix, 79
◊◊The rectum, 81
◊◊Arterial supply of the intestine, 86
◊◊The portal system of veins, 87
◊◊Lymph drainage of the intestine, 88
◊◊The structure of the alimentary canal, 88
◊◊The development of the intestine and its congenital abnormalities, 90
The gastrointestinal adnexae: liver, gall-bladder and its
ducts, pancreas and spleen, 93
◊◊The liver, 93
◊◊The biliary system, 98
◊◊The gall-bladder, 99
◊◊The pancreas, 101
◊◊The spleen, 104
The urinary tract, 105
◊◊The kidneys, 105
◊◊The ureter, 109
◊◊The embryology and congenital abnormalities of the kidney and
ureter, 110
◊◊The bladder, 112
◊◊The urethra, 115
The male genital organs, 116
◊◊The prostate, 116
◊◊The scrotum, 119
◊◊Testis and epididymis, 119
◊◊Vas deferens (ductus deferens), 123
◊◊The seminal vesicles, 124
The bony and ligamentous pelvis, 124
◊◊The os innominatum, 124
◊◊The sacrum, 125
◊◊The coccyx, 126
◊◊The functions of the pelvis, 126
vi Contents
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◊◊Joints and ligamentous connections of the pelvis, 127
◊◊Differences between the male and female pelvis, 128
◊◊Obstetrical pelvic measurements, 128
◊◊Variations of the pelvic shape, 130
The muscles of the pelvic floor and perineum, 132
◊◊The anterior (urogenital) perineum, 133
◊◊The posterior (anal) perineum, 134
The female genital organs, 136
◊◊The vulva, 136
◊◊The vagina, 137
◊◊The uterus, 139
◊◊The Fallopian tubes, 144
◊◊The ovary, 145
◊◊The endopelvic fascia and the pelvic ligaments, 146
◊◊Vaginal examination, 147
◊◊Embryology of the Fallopian tubes, uterus and vagina, 148
The posterior abdominal wall, 149
◊◊The suprarenal glands, 151
◊◊Abdominal aorta, 151
◊◊Inferior vena cava, 153
◊◊Lumbar sympathetic chain, 153
Part 3:◊The Upper Limb
The female breast, 159
◊◊Structure, 159
◊◊Blood supply, 159
◊◊Lymphatic drainage, 159
◊◊Development, 161
Surface anatomy and surface markings of the
upper limb, 162
◊◊Bones and joints, 163
◊◊Muscles and tendons, 164
◊◊Vessels, 166
◊◊Nerves, 167
The bones and joints of the upper limb, 168
◊◊The scapula, 168
◊◊The clavicle, 168
◊◊The humerus, 169
◊◊The radius and ulna, 171
◊◊The bones of the hand, 174
◊◊The shoulder, 176
◊◊The elbow joints, 180
Contents
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◊◊The wrist joint, 183
◊◊The joints of the hand, 184
The arteries of the upper limb, 186
◊◊The axillary artery, 186
◊◊The brachial artery, 187
◊◊The radial artery, 187
◊◊The ulnar artery, 188
The brachial plexus, 189
◊◊The segmental cutaneous supply of the upper limb, 191
The course and distribution of the principal nerves of the
upper limb, 191
◊◊The axillary nerve, 191
◊◊The radial nerve, 192
◊◊Branches, 194
◊◊The musculocutaneous nerve, 194
◊◊The ulnar nerve, 194
◊◊The median nerve, 195
The anatomy of upper limb deformities, 197
The spaces of the hand, 200
◊◊The superficial pulp space of the fingers, 200
◊◊The ulnar and radial bursae and the synovial tendon sheaths of the
fingers, 201
Part 4:◊The Lower Limb
The anatomy and surface markings of the lower limb, 207
◊◊Bones and joints, 207
◊◊Bursae of the lower limb, 207
◊◊Mensuration in the lower limb, 208
◊◊Muscles and tendons, 211
◊◊Vessels, 211
◊◊Nerves, 214
The bones and joints of the lower limb, 216
◊◊The os innominatum, 216
◊◊The femur, 216
◊◊The patella, 220
◊◊The tibia, 223
◊◊The fibula, 224
◊◊A note on growing ends and nutrient foramina in the long bones, 225
◊◊The bones of the foot, 225
◊◊The hip, 226
viii Contents
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Contents
ix
◊◊The knee joint, 229
◊◊The tibiofibular joints, 233
◊◊The ankle, 233
◊◊The joints of the foot, 234
◊◊The arches of the foot, 235
◊◊The anatomy of walking, 237
Three important zones of the lower limb—the femoral
triangle, adductor canal and popliteal fossa, 237
◊◊The femoral triangle, 237
◊◊The fascia lata, 238
◊◊The femoral sheath and femoral canal, 238
◊◊Femoral hernia, 239
◊◊The lymph nodes of the groin and the lymphatic drainage of the lower
limb, 241
◊◊The adductor canal (of Hunter) or subsartorial canal, 242
◊◊The popliteal fossa, 242
The arteries of the lower limb, 244
◊◊Femoral artery, 244
◊◊Popliteal artery, 246
◊◊Posterior tibial artery, 246
◊◊Anterior tibial artery, 246
The veins of the lower limb, 247
◊◊Clinical features, 249
The course and distribution of the principal nerves of the
lower limb, 249
◊◊The lumbar plexus, 250
◊◊The sacral plexus, 251
◊◊The sciatic nerve, 253
◊◊The tibial nerve, 255
◊◊The common peroneal (fibular) nerve, 255
◊◊Segmental cutaneous supply of the lower limb, 256
Part 5:◊The Head and Neck
The surface anatomy of the neck, 261
◊◊The fascial compartments of the neck, 262
The thyroid gland, 264
◊◊The parathyroid glands, 267
The palate, 270
◊◊The development of the face, lips and palate with special reference to
their congenital deformities, 270
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The tongue and floor of the mouth, 272
◊◊The tongue, 272
◊◊The floor of the mouth, 276
The pharynx, 277
◊◊The nasopharynx, 277
◊◊The oropharynx, 278
◊◊The palatine tonsils, 279
◊◊The laryngopharynx, 280
◊◊The mechanism of deglutition, 282
The larynx, 284
◊◊Blood supply, 287
◊◊Lymph drainage, 287
◊◊Nerve supply, 288
The salivary glands, 289
◊◊The parotid gland, 289
◊◊The submandibular gland, 292
◊◊The sublingual gland, 293
The major arteries of the head and neck, 294
◊◊The common carotid arteries, 294
◊◊The external carotid artery, 294
◊◊The internal carotid artery, 296
◊◊The subclavian arteries, 298
The veins of the head and neck, 301
◊◊The cerebral venous system, 301
◊◊The venous sinuses of the dura, 301
◊◊The internal jugular vein, 303
◊◊The subclavian vein, 305
The lymph nodes of the neck, 306
The cervical sympathetic trunk, 308
The branchial system and its derivatives, 310
◊◊Branchial cyst and fistula, 310
The surface anatomy and surface markings of the head, 311
The scalp, 312
The skull, 314
◊◊Development, 316
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Contents
xi
The accessory nasal sinuses, 318
◊◊The frontal sinuses, 318
◊◊The maxillary sinus (antrum of Highmore), 319
◊◊The ethmoid sinuses, 320
◊◊The sphenoid sinuses, 321
The mandible, 321
◊◊The temporomandibular joint, 322
◊◊The teeth, 323
The vertebral column, 324
◊◊The cervical vertebrae, 325
◊◊The thoracic vertebrae, 327
◊◊The lumbar vertebrae, 327
◊◊The sacrum, 327
◊◊The coccyx, 327
◊◊The intervertebral joints, 328
Part 6:◊The Central Nervous System
The spinal cord, 333
◊◊Age differences, 333
◊◊Structure, 333
◊◊Descending tracts, 334
◊◊Ascending tracts, 336
◊◊The membranes of the cord (the meninges), 337
The brain, 339
◊◊The medulla, 339
◊◊The pons, 342
◊◊The cerebellum, 342
◊◊The midbrain, 344
◊◊The diencephalon, 346
◊◊The hypothalamus, 346
◊◊The pituitary gland (hypophysis cerebri), 347
◊◊The thalamus, 349
◊◊The cerebral hemispheres, 349
◊◊The cerebral cortex, 349
◊◊The insula, 352
◊◊The connections of the cerebral cortex, 352
◊◊The basal ganglia, 353
◊◊The long ascending and descending pathways, 354
◊◊The membranes of the brain (the meninges), 360
◊◊The ventricular system and the cerebrospinal fluid circulation, 361
The cranial nerves, 364
◊◊The olfactory nerve (I), 364
◊◊The optic nerve (II) and the visual pathway, 365
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◊◊The oculomotor nerve (III), 366
◊◊The trochlear nerve (IV), 368
◊◊The trigeminal nerves (V), 369
◊◊The abducent nerve (VI), 374
◊◊The facial nerve (VII), 375
◊◊The auditory (vestibulocochlear) nerve (VIII), 377
◊◊The glossopharyngeal nerve (IX), 379
◊◊The vagus nerve (X), 379
◊◊The accessory nerve (XI), 381
◊◊The hypoglossal nerve (XII), 381
The special senses, 383
◊◊The nose, 383
◊◊The ear, 384
◊◊The eye and associated structures, 388
The autonomic nervous system, 393
◊◊Visceral afferents, 396
◊◊The sympathetic system, 396
◊◊The sympathetic trunk, 396
◊◊The parasympathetic system, 399
Glossary of eponyms, 403
Index, 409
xii Contents
Preface
Experience of teaching clinical students at five medical schools and of
examining them in sixteen cities and in eight countries has convinced me
that there is still an unfortunate hiatus between the anatomy which the
student learns in the pre-clinical years and that which is later encountered
in the wards and operating theatres.
This book attempts to counter this situation. It does so by highlighting
those features of anatomy which are of clinical importance using a vertical
blue bar, in radiology, pathology, medicine and midwifery as well as in
surgery. It presents the facts which students might reasonably be expected
to carry with them during their years on the wards, through their final
examinations and into their postgraduate years; it is designed for the clini-
cal student.
Anatomy is a vast subject and, therefore, in order to achieve this goal, I
have deliberately carried out a rigorous selection of material so as to cover
only those of its thousands of facts which I consider form the necessary
anatomical scaffolding for the clinician. Wherever possible practical appli-
cations are indicated throughout the text — they cannot, within the limita-
tions of a book of this size, be exhaustive, but I hope that they will act as
signposts to the student and indicate how many clinical phenomena can be
understood and remembered on simple anatomical grounds.
In this eleventh edition a complete revision of the text has been carried
out. New figures have been added and other illustrations modified. Repre-
sentative computerized axial tomography and magnetic resonance
imaging films have been included, since these techniques have given
increased impetus to the clinical importance of topographical anatomy.
The continued success of this volume, now in its forty-seventh year of
publication, owes much to the helpful comments which the author has
received from readers all over the world. Every suggestion is given the
most careful consideration in an attempt to keep the material abreast of the
needs of today’s medical students.
Harold Ellis
2006
xiii
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Acknowledgements
xiv
I wish to thank the many students who have sent suggestions to me, many
of which have been incorporated into this new edition.
To Mrs Katherine Ellis go my grateful thanks for invaluable secretarial
assistance. New and revised illustrations were skilfully produced by Jane
Fallows and new MR scans were provided by Dr Sheila Rankin of the
Department of Radiology at Guy’s Hospital and Professor Adrian Dixon of
Cambridge.
I am grateful to the following authors for permission to reproduce illus-
trations:
The late Lord Brock for Figs 20 and 21 (from Lung Abscess); and
Professor R. G. Harrison for Figs 12, 32 and 69 (from A Textbook of Human
Embryology).
Dr Colin Stolkin gave valuable help in revising the anatomy of the
C.N.S.
Finally, I wish to express my debt to Martin Sugden and the staff of
Blackwell Publishing for their continued and unfailing help.
Harold Ellis
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Part 1
The Thorax
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Surface anatomy and
surface markings
The experienced clinician spends much of his working life relating the
surface anatomy of his patients to their deep structures (Fig. 1; see also
Figs. 11 and 22).
The following bony prominences can usually be palpated in the living
subject (corresponding vertebral levels are given in brackets):
•◊◊superior angle of the scapula (T2);
•◊◊upper border of the manubrium sterni, the suprasternal notch (T2/3);
•◊◊spine of the scapula (T3);
•◊◊sternal angle (of Louis) — the transverse ridge at the manubrio-sternal
junction (T4/5);
•◊◊inferior angle of scapula (T8);
•◊◊xiphisternal joint (T9);
•◊◊lowest part of costal margin—10th rib (the subcostal line passes through
L3).
Note from Fig. 1 that the manubrium corresponds to the 3rd and 4th
thoracic vertebrae and overlies the aortic arch, and that the sternum corre-
sponds to the 5th to 8th vertebrae and neatly overlies the heart.
Since the 1st and 12th ribs are difficult to feel, the ribs should be enu-
merated from the 2nd costal cartilage, which articulates with the sternum at
the angle of Louis.
The spinous processes of all the thoracic vertebrae can be palpated in
the midline posteriorly, but it should be remembered that the first spinous
process that can be felt is that of C7 (the vertebra prominens).
The position of the nipple varies considerably in the female, but in the
male it usually lies in the 4th intercostal space about 4in (10cm) from the
midline. The apex beat, which marks the lowest and outermost point at
which the cardiac impulse can be palpated, is normally in the 5th inter-
costal space 3.5in (9cm) from the midline (just below and medial to the
nipple).
The trachea is palpable in the suprasternal notch midway between the
heads of the two clavicles.
Surface markings of the more important
thoracic contents (Figs 2–4)
The trachea
The trachea commences in the neck at the level of the lower border of the
cricoid cartilage (C6) and runs vertically downwards to end at the level of
the sternal angle of Louis (T4/5), just to the right of the mid-line, by divid-
ing to form the right and left main bronchi. In the erect position and in full
inspiration the level of bifurcation is at T6.
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4 The Thorax
Fig. 1◊Lateral view of the
thorax—its surface
markings and vertebral
levels. (Note that the
angle of Louis (T4/5)
demarcates the superior
mediastinum, the upper
margin of the heart and
the beginning and end of
the aortic arch.)
Fig. 2◊The surface markings of the lungs and pleura—anterior view.
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Surface anatomy and surface markings
5
The pleura
The cervical pleura can be marked out on the surface by a curved line drawn
from the sternoclavicular joint to the junction of the medial and middle
thirds of the clavicle; the apex of the pleura is about 1 in (2.5cm) above
the clavicle. This fact is easily explained by the oblique slope of the first rib.
It is important because the pleura can be wounded (with consequent
Fig. 3◊The surface
markings of the lungs
and pleura—posterior
view.
Fig. 4◊The surface
markings of the heart (see
text).
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pneumothorax) by a stab wound — and this includes the surgeon’s knife
and the anaesthetist’s needle—above the clavicle.
The lines of pleural reflexion pass from behind the sternoclavicular joint
on each side to meet in the midline at the 2nd costal cartilage (the angle of
Louis). The right pleural edge then passes vertically downwards to the 6th
costal cartilage and then crosses:
•◊◊the 8th rib in the midclavicular line;
•◊◊the 10th rib in the midaxillary line;
•◊◊the 12th rib at the lateral border of the erector spinae.
On the left side the pleural edge arches laterally at the 4th costal carti-
lage and descends lateral to the border of the sternum, due, of course, to its
lateral displacement by the heart; apart from this, its relationships are those
of the right side.
The pleura actually descends just below the 12th rib margin at its
medial extremity — or even below the edge of the 11th rib if the 12th is
unusually short; obviously in this situation the pleura may be opened acci-
dentally in making a loin incision to expose the kidney, perform an adrena-
lectomy or to drain a subphrenic abscess.
The lungs
The surface projection of the lung is somewhat less extensive than that of
the parietal pleura as outlined above, and in addition it varies quite consid-
erably with the phase of respiration. The apex of the lung closely follows the
line of the cervical pleura and the surface marking of the anterior border of the
right lung corresponds to that of the right mediastinal pleura. On the left
side, however, the anterior border has a distinct notch (the cardiac notch)
which passes behind the 5th and 6th costal cartilages. The lower border of the
lung has an excursion of as much as 2–3in (5–8cm) in the extremes of respi-
ration, but in the neutral position (midway between inspiration and expira-
tion) it lies along a line which crosses the 6th rib in the midclavicular line,
the 8th rib in the midaxillary line, and reaches the 10th rib adjacent to the
vertebral column posteriorly.
The oblique fissure, which divides the lung into upper and lower lobes, is
indicated on the surface by a line drawn obliquely downwards and out-
wards from 1in (2.5cm) lateral to the spine of the 5th thoracic vertebra to
the 6th costal cartilage about 1.5in (4cm) from the midline. This can be rep-
resented approximately by abducting the shoulder to its full extent; the line
of the oblique fissure then corresponds to the position of the medial border
of the scapula.
The surface markings of the transverse fissure (separating the middle and
upper lobes of the right lung) is a line drawn horizontally along the 4th
costal cartilage and meeting the oblique fissure where the latter crosses the
5th rib.
The heart
The outline of the heart can be represented on the surface by the
irregular quadrangle bounded by the following four points (Fig. 4):
6 The Thorax
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The thoracic cage
7
1◊◊the 2nd left costal cartilage 0.5in (12mm) from the edge of the sternum;
2◊◊the 3rd right costal cartilage 0.5in (12mm) from the sternal edge;
3◊◊the 6th right costal cartilage 0.5in (12mm) from the sternum;
4◊◊the 5th left intercostal space 3.5in (9cm) from the midline (correspond-
ing to the apex beat).
The left border of the heart (indicated by the curved line joining points
1 and 4) is formed almost entirely by the left ventricle (the auricular
appendage of the left atrium peeping around this border superiorly), the
lower border (the horizontal line joining points 3 and 4) corresponds to the
right ventricle and the apical part of the left ventricle; the right border
(marked by the line joining points 2 and 3) is formed by the right atrium
(see Fig. 24a).
A good guide to the size and position of your own heart is given by
placing your clenched right fist palmar surface down immediately inferior
to the manubriosternal junction. Note that the heart is about the size of the
subject’s fist, lies behind the body of the sternum (therefore anterior to tho-
racic vertebrae 5–8), and bulges over to the left side.
The surface markings of the vessels of the thoracic wall are of im-
portance if these structures are to be avoided in performing aspiration
of the chest. The internal thoracic (internal mammary) vessels run vertically
downwards behind the costal cartilages half an inch from the lateral
border of the sternum. The intercostal vessels lie immediately below
their corresponding ribs (the vein above the artery) so that it is safe to pass
a needle immediately above a rib, dangerous to pass it immediately below
(see Fig. 8).
The thoracic cage
The thoracic cage is formed by the vertebral column behind, the ribs and
intercostal spaces on either side and the sternum and costal cartilages in
front. Above, it communicates through the ‘thoracic inlet’ with the root
of the neck; below, it is separated from the abdominal cavity by the
diaphragm (Fig. 1).
The thoracic vertebrae
See ‘vertebral column’, page 327.
The ribs
The greater part of the thoracic cage is formed by the twelve pairs of ribs.
Of these, the first seven are connected anteriorly by way of their costal
cartilages to the sternum, the cartilages of the 8th, 9th and 10th articulate
each with the cartilage of the rib above (‘false ribs’) and the last two ribs are
free anteriorly (‘floating ribs’).
Each typical rib (Fig. 5) has a head bearing two articular facets, for
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articulation with the numerically corresponding vertebra and the vertebra
above, a stout neck, which gives attachment to the costotransverse liga-
ments, a tubercle with a rough non-articular portion and a smooth facet, for
articulation with the transverse process of the corresponding vertebra, and
a long shaft flattened from side to side and divided into two parts by the
‘angle’ of the rib. The angle demarcates the lateral limit of attachment of the
erector spinae muscle.
The following are the significant features of the ‘atypical’ ribs.
1st Rib (Fig. 6). This is flattened from above downwards. It is not
only the flattest but also the shortest and most curvaceous of all the ribs. It
has a prominent tubercle on the inner border of its upper surface for the
8 The Thorax
Fig. 5◊A typical rib.
Fig. 6◊Structures crossing the first rib.
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insertion of scalenus anterior. In front of this tubercle, the subclavian vein
crosses the rib; behind the tubercle is the subclavian groove where the subcla-
vian artery and lowest trunk of the brachial plexus lie in relation to the
bone. It is here that the anaesthetist can infiltrate the plexus with local
anaesthetic.
Crossing the neck of the first rib from the medial to the lateral side are
the sympathetic trunk, the superior intercostal artery (from the costocervi-
cal trunk) and the large branch of the first thoracic nerve to the brachial
plexus.
The 2nd rib is much less curved than the 1st and about twice as long.
The 10th rib has only one articular facet on the head.
The 11th and 12th ribs are short, have no tubercles and only a single facet
on the head. The 11th rib has a slight angle and a shallow subcostal groove;
the 12th has neither of these features.
Clinical features
Rib fractures
The chest wall of the child is highly elastic and therefore fractures of the rib
in children are rare. In adults, the ribs may be fractured by direct violence or
indirectly by crushing injuries; in the latter the rib tends to give way at its
weakest part in the region of its angle. Not unnaturally, the upper two ribs,
which are protected by the clavicle, and the lower two ribs, which are unat-
tached and therefore swing free, are the least commonly injured.
In a severe crush injury to the chest several ribs may fracture in front
and behind so that a whole segment of the thoracic cage becomes torn free
(‘stove-in chest’). With each inspiration this loose flap sucks in, with each
expiration it blows out, thus undergoing paradoxical respiratory move-
ment. The associated swinging movements of the mediastinum produce
severe shock and this injury calls for urgent treatment by insertion of a
chest drain with underwater seal, followed by endotracheal intubation, or
tracheostomy, combined with positive pressure respiration.
Coarctation of the aorta (see Fig. 34b and page 41)
In coarctation of the aorta, the intercostal arteries derived from the aorta
receive blood from the superior intercostals (from the costocervical trunk of
the subclavian artery), from the anterior intercostal branches of the internal
thoracic artery (arising from the subclavian artery) and from the arteries
anastomosing around the scapula. Together with the communication
between the internal thoracic and inferior epigastric arteries, they provide
the principal collaterals between the aorta above and below the block. In
consequence, the intercostal arteries undergo dilatation and tortuosity and
erode the lower borders of the corresponding ribs to give the characteristic
irregular notching of the ribs, which is very useful in the radiographic confir-
mation of this lesion.
The thoracic cage
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Fig. 7◊Bilateral cervical ribs. On the right side the brachial plexus is shown arching
over the rib and stretching its lowest trunk.
Cervical rib
A cervical rib (Fig. 7) occurs in 0.5% of subjects and is bilateral in half of
these. It is attached to the transverse process of the 7th cervical vertebra and
articulates with the 1st (thoracic) rib or, if short, has a free distal extremity
which usually attaches by a fibrous strand to the (normal) first rib. Pressure
of such a rib on the lowest trunk of the brachial plexus arching over it may
produce paraesthesiae along the ulnar border of the forearm and wasting of
the small muscles of the hand (T1). Less commonly vascular changes, even
gangrene, may be caused by pressure of the rib on the overlying subclavian
artery. This results in post-stenotic dilatation of the vessel distal to the rib in
which a thrombus forms from which emboli are thrown off.
The costal cartilages
These bars of hyaline cartilage serve to connect the upper seven ribs
directly to the side of the sternum and the 8th, 9th and 10th ribs to
the cartilage immediately above. The cartilages of the 11th and 12th ribs
merely join the tapered extremities of these ribs and end in the abdominal
musculature.
10 The Thorax
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Clinical features
1◊◊The cartilage adds considerable resilience to the thoracic cage and pro-
tects the sternum and ribs from more frequent fracture.
2◊◊In old age (and sometimes also in young adults) the costal cartilages
undergo progressive ossification; they then become radio-opaque and may
give rise to some confusion when examining a chest radiograph of an
elderly patient.
The sternum
This dagger-shaped bone, which forms the anterior part of the thoracic
cage, consists of three parts. The manubrium is roughly triangular in outline
and provides articulation for the clavicles and for the first and upper part of
the 2nd costal cartilages on either side. It is situated opposite the 3rd and
4th thoracic vertebrae. Opposite the disc between T4 and T5 it articulates at
an oblique angle at the manubriosternal joint (the angle of Louis), with the
body of the sternum (placed opposite T5 to T8). This is composed of four parts
or ‘sternebrae’ which fuse between puberty and 25 years of age. Its lateral
border is notched to receive part of the 2nd and the 3rd to the 7th costal car-
tilage. The xiphoid process is the smallest part of the sternum and usually
remains cartilaginous well into adult life. The cartilaginous manu-
briosternal joint and that between the xiphoid and the body of the sternum
may also become ossified after the age of 30.
Clinical features
1◊◊The attachment of the elastic costal cartilages largely protects the
sternum from injury, but indirect violence accompanying fracture disloca-
tion of the thoracic spine may be associated with a sternal fracture. Direct
violence to the sternum may lead to displacement of the relatively mobile
body of the sternum backwards from the relatively fixed manubrium.
2◊◊In a sternal puncture a wide-bore needle is pushed through the thin
layer of cortical bone covering the sternum into the highly vascular spongy
bone beneath, and a specimen of bone marrow aspirated with a syringe.
3◊◊In operations on the thymus gland, and occasionally for a retrosternal
goitre, it is necessary to split the manubrium in the midline in order to gain
access to the superior mediastinum. A complete vertical split of the whole
sternum is one of the standard approaches to the heart and great vessels
used in modern cardiac surgery.
The intercostal spaces
There are slight variations between the different intercostal spaces, but typi-
cally each space contains three muscles, comparable to those of the abdomi-
nal wall, and an associated neurovascular bundle (Fig. 8). The muscles are:
The thoracic cage
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1◊◊the external intercostal, the fibres of which pass downwards and
forwards from the rib above to the rib below and reach from the vertebrae
behind to the costochondral junction in front, where muscle is replaced by
the anterior intercostal membrane;
2◊◊the internal intercostal, which runs downwards and backwards from the
sternum to the angles of the ribs where it becomes the posterior intercostal
membrane;
3◊◊the innermost intercostal, which is only incompletely separated from the
internal intercostal muscle by the neurovascular bundle.
The fibres of this sheet cross more than one intercostal space and it may be
incomplete. Anteriorly it has a more distinct portion which is fan-like in
shape, termed the transversus thoracis (or sternocostalis), which spreads
upwards from the posterior aspect of the lower sternum to insert onto the
inner surfaces of the second to the sixth costal cartilages.
Just as in the abdomen, the nerves and vessels of the thoracic wall lie
between the middle and innermost layers of muscles. This neurovascular
bundle consists, from above downwards, of vein, artery and nerve, the vein
lying in a groove on the undersurface of the corresponding rib (remember—
v,a,n).
The vessels comprise the posterior and anterior intercostals.
The posterior intercostal arteries of the lower nine spaces are branches of
the thoracic aorta, while the first two are derived from the superior inter-
costal branch of the costocervical trunk, the only branch of the second part
of the subclavian artery. Each runs forward in the subcostal groove to anas-
tomose with the anterior intercostal artery. Each has a number of branches
to adjacent muscles, to the skin and to the spinal cord. The corresponding
veins are mostly tributaries of the azygos and hemiazygos veins. The first
posterior intercostal vein drains into the brachiocephalic or vertebral vein.
12 The Thorax
Fig. 8◊The relationship
of an intercostal space.
(Note that a needle
passed into the chest
immediately above a
rib will avoid the
neurovascular bundle.)
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2
On the left, the 2nd and 3rd veins often join to form a superior intercostal
vein, which crosses the aortic arch to drain into the left brachiocephalic
vein.
The anterior intercostal arteries are branches of the internal thoracic artery
(1st–6th space) or of its musculophrenic branch (7th–9th spaces). The
lowest two spaces have only posterior arteries. Perforating branches pierce
the upper five or six intercostal spaces; those of the 2nd–4th spaces are large
in the female and supply the breast.
The intercostal nerves are the anterior primary rami of the thoracic
nerves, each of which gives off a collateral muscular branch and lateral and
anterior cutaneous branches for the innervation of the thoracic and abdom-
inal walls (Fig. 9).
Clinical features
1◊◊Local irritation of the intercostal nerves by such conditions as Pott’s
disease of the thoracic vertebrae (tuberculosis) may give rise to pain which
is referred to the front of the chest or abdomen in the region of the periph-
eral termination of the nerves.
2◊◊Local anaesthesia of an intercostal space is easily produced by infiltra-
tion around the intercostal nerve trunk and its collateral branch — a proce-
dure known as intercostal nerve block.
The thoracic cage
13
Fig. 9◊Diagram of a typical spinal nerve and its body-wall relationships. On the left
side the sites of eruption of a tuberculous cold abscess tracking forwards from a
diseased vertebra are shown—these occur at the points of emergence of the
cutaneous branches.
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3◊◊In a conventional posterolateral thoracotomy (e.g. for a pulmonary
lobectomy) an incision is made along the line of the 5th or 6th rib; the
periosteum over a segment of the rib is elevated, thus protecting the neu-
rovascular bundle, and the rib is excised. Access to the lung or medi-
astinum is then gained though the intercostal space, which can be opened
out considerably owing to the elasticity of the thoracic cage.
4◊◊Pus from the region of the vertebral column tends to track around the
thorax along the course of the neurovascular bundle and to ‘point’ to the
three sites of exit of the cutaneous branches of the intercostal nerves, which
are lateral to erector spinae (sacrospinalis), in the midaxillary line and just
lateral to the sternum (Fig. 9).
The diaphragm
The diaphragm is the dome-shaped septum dividing the thoracic from the
abdominal cavity. It comprises two portions: a peripheral muscular part
which arises from the margins of the thoracic outlet and a centrally placed
aponeurosis (Fig. 10).
The muscular fibres are arranged in three parts.
1◊◊A vertebral part from the crura and from the arcuate ligaments. The right
crus arises from the front of the bodies of the upper three lumbar vertebrae
and intervertebral discs; the left crus is only attached to the first two verte-
brae. The arcuate ligaments are a series of fibrous arches, the medial being a
thickening of the fascia covering psoas major and the lateral of fascia overly-
ing quadratus lumborum. The fibrous medial borders of the two crura form
a median arcuate ligament over the front of the aorta.
2◊◊A costal part is attached to the inner aspect of the lower six ribs and costal
cartilages.
3◊◊A sternal portion consists of two small slips from the deep surface of the
xiphisternum.
The central tendon, into which the muscular fibres are inserted, is trefoil
in shape and is partially fused with the undersurface of the pericardium.
The diaphragm receives its entire motor supply from the phrenic nerve
(C3, 4, 5) whose long course from the neck follows the embryological
migration of the muscle of the diaphragm from the cervical region (see
below). Injury or operative division of this nerve results in paralysis and
elevation of the corresponding half of the diaphragm.
Radiographically, paralysis of the diaphragm is recognized by its eleva-
tion and paradoxical movement; instead of descending on inspiration it is
forced upwards by pressure from the abdominal viscera.
The sensory nerve fibres from the central part of the diaphragm also
run in the phrenic nerve, hence irritation of the diaphragmatic pleura (in
pleurisy) or of the peritoneum on the undersurface of the diaphragm by
subphrenic collections of pus or blood produces referred pain in the corre-
sponding cutaneous area, the shoulder-tip.
The peripheral part of the diaphragm, including the crura, receives
sensory fibres from the lower intercostal nerves.
14 The Thorax
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Openings in the diaphragm
The three main openings in the diaphragm (Figs 10, 11) are:
1◊◊the aortic (at the level of T12) which transmits the abdominal aorta, the
thoracic duct and often the azygos vein;
2◊◊the oesophageal (T10) which is situated between the muscular fibres of
the right crus of the diaphragm and transmits, in addition to the oesopha-
gus, branches of the left gastric artery and vein and the two vagi;
3◊◊the opening for the inferior vena cava (T8) which is placed in the central
tendon and also transmits the right phrenic nerve.
In addition to these structures, the greater and lesser splanchnic nerves
(see page 49) pierce the crura and the sympathetic chain passes behind the
diaphragm deep to the medial arcuate ligament.
The development of the diaphragm
and the anatomy of diaphragmatic herniae
The diaphragm is formed (Fig. 12) by fusion in the embryo of:
1◊◊the septum transversum (forming the central tendon);
2◊◊the dorsal oesophageal mesentery;
3◊◊a peripheral rim derived from the body wall;
4◊◊the pleuroperitoneal membranes, which close the fetal communication
between the pleural and peritoneal cavities.
The septum transversum is the mesoderm which, in early develop-
ment, lies in front of the head end of the embryo. With the folding off of the
head, this mesodermal mass is carried ventrally and caudally, to lie in its
The thoracic cage
15
Oesophagus
Left phrenic nerve
Vagi
Aorta
Left splanchnic
nerve
Subcostal nerve
Sympathetic trunk
Inferior vena cava
Right phrenic nerve
Right splanchnic
nerve
Transverse abdominis
muscle
Quadratus lumborum
muscle
Psoas major
muscle
Fig. 10◊The diaphragm—inferior aspect. The three major orifices, from above
downwards, transmit the inferior vena cava, oesophagus and aorta.
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16 The Thorax
Fig. 11◊Schematic lateral
view of the diaphragm to
show the levels at which
it is pierced by major
structures.
Fig. 12◊The development of the diaphragm. This drawing shows the four elements
contributing to the diaphragm—(1) the septum transversum, (2) the dorsal
mesentery of the oesophagus, (3) the body wall and (4) the pleuroperitoneal
membrane.
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definitive position at the anterior part of the diaphragm. During this migra-
tion, the cervical myotomes and nerves contribute muscle and nerve
supply respectively, thus accounting for the long course of the phrenic
nerve (C3, 4 and 5) from the neck to the diaphragm.
With such a complex embryological story, one may be surprised to
know that congenital abnormalities of the diaphragm are unusual.
However, a number of defects may occur, giving rise to a variety of con-
genital herniae through the diaphragm. These may be:
1◊◊through the foramen of Morgagni; anteriorly between the xiphoid and
costal origins;
2◊◊through the foramen of Bochdalek — the pleuroperitoneal canal — lying
posteriorly;
3◊◊through a deficiency of the whole central tendon (occasionally such a
hernia may be traumatic in origin);
4◊◊through a congenitally large oesophageal hiatus.
Far more common are the acquired hiatus herniae (subdivided into
sliding and rolling herniae). These are found in patients usually of middle
age where weakening and widening of the oesophageal hiatus has
occurred (Fig. 13).
In the sliding hernia the upper stomach and lower oesophagus slide
upwards into the chest through the lax hiatus when the patient lies down or
bends over; the competence of the cardia is often disturbed and peptic juice
can therefore regurgitate into the gullet in lying down or bending over. This
may be followed by oesophagitis with consequent heartburn, bleeding and,
eventually, stricture formation.
In the rolling hernia (which is far less common) the cardia remains in its
normal position and the cardio-oesophageal junction is intact, but the
fundus of the stomach rolls up through the hiatus in front of the oesopha-
gus, hence the alternative term of para-oesophageal hernia. In such a case
The thoracic cage
17
Fig. 13◊(a) A sliding hiatus hernia. (b) A rolling hiatus hernia.
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there may be epigastric discomfort, flatulence and even dysphagia, but no
regurgitation because the cardiac mechanism is undisturbed.
The movements of respiration
During inspiration the movements of the chest wall and diaphragm result
in an increase in all diameters of the thorax. This, in turn, brings about an
increase in the negative intrapleural pressure and an expansion of the lung
tissue. Conversely, in expiration the relaxation of the respiratory muscles
and the elastic recoil of the lung reduce the thoracic capacity and force air
out of the lungs.
In quiet inspiration the first rib remains relatively fixed, but contraction
of the external and internal intercostals elevates and, at the same time,
everts the succeeding ribs. In the case of the 2nd–7th ribs this principally
increases the anteroposterior diameter of the thorax (by the forward
thrust of the sternum), like a pump handle. The corresponding movement
of the lower ribs raises the costal margin and leads mainly to an increase in
the transverse diameter of the thorax, like a bucket handle. The depth of the
thorax is increased by the contraction of the diaphragm which draws down
its central tendon. Normal quiet expiration, brought about by elastic recoil of
the elevated ribs, is aided by the tone of the abdominal musculature which,
acting through the contained viscera, forces the diaphragm upwards.
In deep and in forced inspiration additional muscles attached to the
chest wall are called into play (e.g. scalenus anterior, sternocleidomastoid,
serratus anterior and pectoralis major) to increase further the capacity of
the thorax. Similarly, in deep expiration, forced contraction of the abdomi-
nal muscles aids the normal expulsive factors described above.
The pleurae
The two pleural cavities are totally separate from each other (Fig. 2). Each
pleura consists of two layers: a visceral layer intimately related to the surface
of the lung, and a parietal layer lining the inner aspect of the chest wall, the
upper surface of the diaphragm and the sides of the pericardium and medi-
astinum. The two layers are continuous in front and behind the root of the
lung, but below this the pleura hangs down in a loose fold, the pulmonary
ligament, which forms a ‘dead-space’ for distension of the pulmonary veins.
The surface markings of the pleura and lungs have already been described
in the section on surface anatomy.
Notice that the lungs do not occupy all the available space in the pleural
cavity even in forced inspiration.
Clinical features
1◊◊Normally the two pleural layers are in close apposition and the space
between them is only a potential one. It may, however, fill with air (pneu-
mothorax), blood (haemothorax) or pus (empyema).
18 The Thorax
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2◊◊Fluid can be drained from the pleural cavity by inserting a wide-bore
needle through an intercostal space (usually the 7th posteriorly). The
needle is passed along the superior border of the lower rib, thus avoiding
the intercostal nerves and vessels (Fig. 8). Below the 7th intercostal space
there is danger of penetrating the diaphragm.
3◊◊For emergency chest drainage— for example traumatic haemothorax or
haemopneumothorax— the site of election is the 5th intercostal space in the
mid-axillary line. An incision is made through skin and fat and blunt dis-
section carried out over the upper border of the 6th rib. The pleura is
opened, a finger inserted to clear any adhesions and ensure the safety of the
adjacent diaphragm before inserting a tube into the pleural space and con-
necting it to an under-water drain.
4◊◊Since the parietal pleura is segmentally innervated by the intercostal
nerves, inflammation of the pleura results in pain referred to the cutaneous
distribution of these nerves (i.e. to the thoracic wall or, in the case of the
lower nerves, to the anterior abdominal wall, which may mimic an acute
abdominal emergency).
The lower respiratory tract
The trachea (Figs 14, 15)
The trachea is about 4.5in (11.5cm) in length and nearly 1 in (2.5cm) in
diameter. It commences at the lower border of the cricoid cartilage (C6) and
terminates by bifurcating at the level of the sternal angle of Louis (T4/5) to
form the right and left main bronchi. (In the living subject, the level of bifur-
cation varies slightly with the phase of respiration; in deep inspiration is
descends to T6 and in expiration it rises to T4.)
Relations
Lying partly in the neck and partly in the thorax, its relations are:
Cervical
•◊◊anteriorly — the isthmus of thyroid gland, inferior thyroid veins, ster-
nohyoid and sternothyroid muscles;
•◊◊laterally—the lobes of thyroid gland and the common carotid artery;
•◊◊posteriorly—the oesophagus with the recurrent laryngeal nerve lying in
the groove between oesophagus and trachea (Fig. 16).
Thoracic
In the superior mediastinum its relations are:
•◊◊anteriorly— commencement of the brachiocephalic (innominate) artery
The lower respiratory tract
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20 The Thorax
Fig. 14◊The trachea and its anterior relationships.
Fig. 15◊The trachea and main bronchi viewed from the front.
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and left carotid artery, both arising from the arch of the aorta, the left bra-
chiocephalic (innominate) vein, and the thymus;
•◊◊posteriorly—oesophagus and left recurrent laryngeal nerve;
•◊◊to the left — arch of the aorta, left common carotid and left subclavian
arteries, left recurrent laryngeal nerve and pleura;
•◊◊to the right—vagus, azygos vein and pleura (Fig. 17).
Structure
The patency of the trachea is maintained by a series of 15–20 U-shaped car-
tilages. Posteriorly, where the cartilage is deficient, the trachea is flattened
and its wall completed by fibrous tissue and a sheet of smooth muscle (the
trachealis). Within, it is lined by a ciliated columnar epithelium with many
goblet cells.
Clinical features
Radiology
Since it contains air, the trachea is more radio-translucent than the neigh-
bouring structures and is seen in posteroanterior and lateral radiographs as
a dark area passing downwards, backwards and slightly to the right. In the
elderly, calcification of the tracheal rings may be a source of radiological
confusion.
Displacement
The trachea may be compressed or displaced by pathological enlargement
The lower respiratory tract
21
Sternocleidomastoid
Carotid sheath (containing
common carotid artery,
internal jugular vein, and
vagus nerve) with sympathetic
chain behind
Sternohyoid
Sternothyroid
Omohyoid
External jugular vein
Pretracheal fascia
(containing thyroid,
trachea, oesophagus
and recurrent nerve)
Anterior jugular
vein
C6
Investing fascia
Pre-vertebral fascia
Fig. 16◊The cervical part
of the trachea and its
environs in transverse
section (through the 6th
cervical vertebra).
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of the neighbouring structures, particularly the thyroid gland and the arch
of the aorta.
‘Tracheal-tug’
The intimate relationship between the arch of the aorta and the trachea and
left bronchus is responsible for the physical sign known as ‘tracheal-tug’,
characteristic of aneurysms of the aortic arch.
Tracheostomy
Tracheostomy may be required for laryngeal obstruction (diphtheria,
tumours, inhaled foreign bodies), for the evacuation of excessive secretions
(severe postoperative chest infection in a patient who is too weak to cough
adequately), and for long-continued artificial respiration (poliomyelitis,
severe chest injuries). It is important to note that respiration is further
assisted by considerable reduction of the dead-space air.
The neck is extended and the head held exactly in the midline by an
assistant. A vertical incision is made downwards from the cricoid cartilage,
passing between the anterior jugular veins. Alternatively, a more cosmetic
transverse skin crease incision, placed halfway between the cricoid and
suprasternal notch, is employed. A hook is thrust under the lower border of
the cricoid to steady the trachea and pull it forward. The pretracheal fascia
is split longitudinally, the isthmus of the thyroid either pushed upwards or
divided between clamps and the cartilage of the trachea clearly exposed. A
circular opening is then made into the trachea to admit the tracheostomy
tube.
22 The Thorax
2nd costal
cartilage
Internal
thoracic artery
and veins
Thymus
Superior
vena cava
Right phrenic
nerve
Azygos vein
Right vagus
nerve
Trachea
Oesophagus
Left phrenic
nerve
Left vagus
nerve
Left recurrent
laryngeal nerve
Aortic arch
Thoracic
duct
T4
Fig. 17◊The thoracic part of the trachea and its environs in transverse section
(through the 4th thoracic vertebra).
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In children the neck is relatively short and the left brachiocephalic vein
may come up above the suprasternal notch so that dissection is rather more
difficult and dangerous. This difficulty is made greater because the child’s
trachea is softer and more mobile than the adult’s and therefore not so
readily identified and isolated. Its softness means that care must be taken,
in incising the child’s trachea, not to let the scalpel plunge through and
damage the underlying oesophagus.
In contrast, the trachea may be ossified in the elderly and small bone
shears required to open into it.
The golden rule of tracheostomy—based entirely on anatomical consid-
erations— is ‘stick exactly to the midline’. If this is not done, major vessels are
in jeopardy and it is possible, although the student may not credit it, to miss
the trachea entirely.
The bronchi (Fig. 15)
The right main bronchus is wider, shorter and more vertical than the left. It is
about 1 in (2.5cm) long and passes directly to the root of the lung at T5.
Before joining the lung it gives off its upper lobe branch, and then passes
below the pulmonary artery to enter the hilum of the lung. It has two
important relations: the azygos vein, which arches over it from behind to
reach the superior vena cava, and the pulmonary artery which lies first
below and then anterior to it.
The left main bronchus is nearly 2 in (5cm) long and passes downwards
and outwards below the arch of the aorta, in front of the oesophagus and
descending aorta. Unlike the right, it gives off no branches until it enters the
hilum of the lung, which it reaches opposite T6. The pulmonary artery
spirals over the bronchus, lying first anteriorly and then above it.
Clinical features
1◊◊The greater width and more vertical course of the right bronchus
accounts for the greater tendency for foreign bodies and aspirated material
to pass into the right bronchus (and thence especially into the middle and
lower lobes of the right lung) rather than into the left.
2◊◊The inner aspect of the whole of the trachea, the main and lobar bronchi
and the commencement of the first segmental divisions can be seen at
bronchoscopy.
3◊◊Widening and distortion of the angle between the bronchi (the carina) as
seen at bronchoscopy is a serious prognostic sign, since it usually indicates
carcinomatous involvement of the tracheobronchial lymph nodes around
the bifurcation of the trachea.
The lungs (Figs 18, 19)
Each lung is conical in shape, having a blunt apex which reaches above
the sternal end of the 1st rib, a concave base overlying the diaphragm,
an extensive costovertebral surface moulded to the form of the chest
The lower respiratory tract
23
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Fig. 18◊The lungs, lateral aspects.
wall and a mediastinal surface which is concave to accommodate the
pericardium.
The right lung is slightly larger than the left and is divided into three
lobes—upper, middle and lower, by the oblique and horizontal fissures. The
left lung has only an oblique fissure and hence only two lobes.
24 The Thorax
Fig. 19◊The lungs, anterior aspects.
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Blood supply
Mixed venous blood is returned to the lungs by the pulmonary arteries; the
air passages are themselves supplied by the bronchial arteries, which are
small branches of the descending aorta. The bronchial arteries, although
small, are of great clinical importance. They maintain the blood supply to
the lung parenchyma after pulmonary embolism, so that, if the patient
recovers, lung function returns to normal.
The superior and inferior pulmonary veins return oxygenated blood to the
left atrium, while the bronchial veins drain into the azygos system.
Lymphatic drainage
The lymphatics of the lung drain centripetally from the pleura towards the
hilum. From the bronchopulmonary lymph nodes in the hilum, efferent lymph
channels pass to the tracheobronchial nodes at the bifurcation of the trachea,
thence to the paratracheal nodes and the mediastinal lymph trunks to drain
usually directly into the brachiocephalic veins or, rarely, indirectly via the
thoracic or right lymphatic duct.
Nerve supply
The pulmonary plexuses derive fibres from both the vagi and the sympa-
thetic trunk. They supply efferents to the bronchial musculature (sympa-
thetic bronchodilator fibres) and receive afferents from the mucous
membrane of the bronchioles and from the alveoli.
The bronchopulmonary segments of the lungs
(Figs 20, 21)
A knowledge of the finer arrangement of the bronchial tree is an essential
The lower respiratory tract
25
Table 1◊The named divisions of the main bronchi.
Apical
Upper lobe bronchus { Posterior
Anterior
Right main bronchus {Middle lobe bronchus
Lateral
{ Medial
Medial (cardiac)
Lower lobe bronchus
Apical
Anterior
{ Basal → { Lateral
Posterior
Upper lobe bronchus
Apicoposterior
↓
{ Anterior
Lingular bronchus
Superior
Left main bronchus {
{ Inferior
Apical
Anterior
Lower lobe bronchus { Basal →
{ Lateral
Posterior
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prerequisite to intelligent appreciation of lung radiology, to interpretation
of bronchoscopy and to the surgical resection of lung segments. Each lobe
of the lung is subdivided into a number of bronchopulmonary segments,
each of which is supplied by a segmental bronchus, artery and vein. These
segments are wedge-shaped with their apices at the hilum and bases at the
lung surface; if excised accurately along their boundaries (which are
marked by intersegmental veins), there is little bleeding or alveolar air
leakage from the raw lung surface.
The names and arrangements of the bronchi are given in Table 1; each
bronchopulmonary segment takes its title from that of its supplying seg-
mental bronchus (listed in the right-hand column of the table).
26 The Thorax
Right
Left
Upper lobe
Upper lobe
◊1◊◊Apical bronchus
◊1◊◊
Apicoposterior bronchus
◊2◊◊Posterior bronchus
◊2◊◊}
◊3◊◊Anterior bronchus
◊3◊◊Anterior bronchus
Middle lobe
Lingula
◊4◊◊Lateral bronchus
◊4◊◊Superior bronchus
◊5◊◊Medial bronchus
◊5◊◊Inferior bronchus
Lower lobe
Lower lobe
◊6◊◊Apical bronchus
◊6◊◊Apical bronchus
◊7◊◊Medial basal
◊◊◊◊(cardiac) bronchus
◊8◊◊Anterior basal
◊8◊◊Anterior basal bronchus
◊◊◊◊bronchus
◊9◊◊Lateral basal
◊9◊◊Lateral basal bronchus
◊◊◊◊bronchus
10◊◊Posterior basal
10◊◊Posterior basal bronchus
◊◊◊◊bronchus
Fig. 20◊The named
divisions of the main
bronchi.
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The left upper lobe has a lingular segment, supplied by the lingular
bronchus from the main upper lobe bronchus. This lobe is equivalent to the
right middle lobe whose bronchus arises as a branch from the main bronchus.
Apart from this, differences between the two sides are very slight; on the
left, the upper lobe bronchus gives off a combined apicoposterior segmen-
tal bronchus and an anterior branch, whereas all three branches are sepa-
rate on the right side.
On the right also there is a small medial (or cardiac) lower lobe
The lower respiratory tract
27
Fig. 21◊(a) The segments of the right lung. (b) The segments of the left lung.
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bronchus which is absent on the left, the lower lobes being otherwise mirror
images of each other.
The mediastinum
The mediastinum is defined as ‘the space which is sandwiched between the
two pleural sacs’. For descriptive purposes the mediastinum is divided by a
line drawn horizontally from the sternal angle to the lower border of T4
(angle of Louis) into superior and inferior mediastinum. The inferior medi-
astinum is further subdivided into the anterior in front of the pericardium,
a middle mediastinum containing the pericardium itself with the heart and
great vessels, and posterior mediastinum between the pericardium and the
lower eight thoracic vertebrae (Fig. 22).
The pericardium
The heart and the roots of the great vessels are contained within the conical
fibrous pericardium, the apex of which is fused with the adventitia of the
28 The Thorax
Fig. 22◊The subdivisions
of the mediastinum.
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great vessels and the base with the central tendon of the diaphragm. Anteri-
orly it is related to the body of the sternum, to which it is attached by the
sternopericardial ligament. The 3rd–6th costal cartilages and the anterior
borders of the lungs; posteriorly, to the oesophagus, descending aorta, and
vertebra T5–T8, and on either side to the roots of the lungs, the mediastinal
pleura and the phrenic nerves.
The inner aspect of the fibrous pericardium is lined by the parietal layer
of serous pericardium. This, in turn, is reflected around the roots of the great
vessels to become continuous with the visceral layer or epicardium. The lines
of pericardial reflexion are marked on the posterior surface of the heart (Fig.
23) by the oblique sinus, bounded by the inferior vena cava and the four pul-
monary veins, which form a recess between the left atrium and the peri-
cardium, and the transverse sinus between the superior vena cava and left
atrium behind and the pulmonary trunk and aorta in front.
The heart (Fig. 24)
Its great importance means no excuse need be offered for dealing with the
heart in considerable detail.
The heart is irregularly conical in shape, and it is placed obliquely in
the middle mediastinum. Viewed from the front, portions of all the heart
chambers can be seen. The right border is formed entirely by the right
atrium, the left border partly by the auricular appendage of the left atrium
but mainly by the left ventricle, and the inferior border chiefly by the right
The mediastinum
29
Fig. 23◊The transverse and oblique sinuses of the pericardium. In this illustration
the heart has been removed from the pericardial sac, which is seen in anterior view.
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ventricle but also by the lower part of the right atrium and the apex of the
left ventricle.
The bulk of the anterior surface is formed by the right ventricle which is
separated from the right atrium by the vertical atrioventricular groove, and
from the left ventricle by the anterior interventricular groove.
30 The Thorax
Fig. 24◊The heart, (a) anterior and (b) posterior aspects.
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The inferior or diaphragmatic surface consists of the right and left ventri-
cles separated by the posterior interventricular groove and the portion of
the right atrium which receives the inferior vena cava.
The base or posterior surface is quadrilateral in shape and is formed
mainly by the left atrium with the openings of the pulmonary veins and, to
a lesser extent, by the right atrium.
Chambers of the heart
Right atrium (Fig. 25)
The right atrium receives the superior vena cava in its upper and posterior
part, the inferior vena cava and coronary sinus in its lower part, and the
anterior cardiac vein (draining much of the front of the heart) anteriorly.
Running more or less vertically downwards between the venae cavae is a
distinct muscular ridge, the crista terminalis (indicated on the outer surface
of the atrium by a shallow groove — the sulcus terminalis). This ridge sepa-
rates the smooth-walled posterior part of the atrium, derived from the
sinus venosus, from the rough-walled anterior portion which is prolonged
into the auricular appendage and which is derived from the true fetal
atrium.
The openings of the inferior vena cava and the coronary sinus are
guarded by rudimentary valves; that of the inferior vena cava being contin-
uous with the annulus ovalis around the shallow depression on the atrial
septum, the fossa ovalis, which marks the site of the fetal foramen ovale.
The mediastinum
31
Fig. 25◊The interior of the right atrium and ventricle.
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Right ventricle (Fig. 25)
The right ventricle is joined to the right atrium by the way of the vertically
disposed tricuspid valve, and with the pulmonary trunk through the pul-
monary valve. A muscular ridge, the infundibuloventricular crest, between
the atrioventricular and pulmonary orifices, separates the ‘inflow’ and
‘outflow’ tracts of the ventricle. The inner aspect of the inflow tract path is
marked in the presence of a number of irregular muscular elevations (tra-
beculae carneae) from some of which the papillary muscles project into the
lumen of the ventricle and find attachment to the free borders of the cusps
of the tricuspid valve by way of the chordae tendineae. The moderator band is a
muscular bundle crossing the ventricular cavity from the interventricular
septum to the anterior wall and is of some importance since it conveys the
right branch of the atrioventricular bundle to the ventricular muscle.
The outflow tract of the ventricle or infundibulum is smooth-walled and
is directed upwards and to the right towards the pulmonary trunk. The
pulmonary orifice is guarded by the pulmonary valves, comprising three
semilunar cusps.
Left atrium
The left atrium is rather smaller than the right but has somewhat thicker
walls. On the upper part of its posterior wall it presents the openings of the
four pulmonary veins and on its septal surface there is a shallow depression
corresponding to the fossa ovalis of the right atrium. As on the right side,
the main part of the cavity is smooth-walled but the surface of the auricle is
marked by a number of ridges due to the underlying pectinate muscles.
Left ventricle (Fig. 26)
The left ventricle communicates with the left atrium by way of the mitral
valve (so-called because it vaguely resembles a bishop’s mitre), which pos-
sesses a large anterior and a smaller posterior cusp attached to papillary
muscles by chordae tendineae. With the exception of the fibrous vestibule
immediately below the aortic orifice, the wall of the left ventricle is marked
by thick trabeculae carneae.
The aortic orifice is guarded by the three semilunar cusps of the aortic
valve, immediately above which are the dilated aortic sinuses. The mouths of
the right and left coronary arteries are seen in the anterior and left posterior
sinus respectively.
The conducting system of the heart
This consists of specialized cardiac muscle found in the sinuatrial node and
in the atrioventricular node and bundle. The heart-beat is initiated in the
sinuatrial node (the ‘pacemaker of the heart’), situated in the upper part
of the crista terminalis just to the right of the opening of the superior
vena cava into the right atrium. From there the cardiac impulse spreads
32 The Thorax
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throughout the atrial musculature to reach the atrioventricular node lying in
the atrial septum immediately above the opening of the coronary sinus. The
impulse is then conducted to the ventricles by way of the specialized tissue
of the atrioventricular bundle (of His). This bundle divides at the junction of
the membranous and muscular parts of the interventricular septum into its
right and left branches which run immediately beneath the endocardium to
activate all parts of the ventricular musculature.
The blood supply to the heart (Fig. 27)
The heart’s blood supply is derived from the right and left coronary arteries
whose main branches lie in the interventricular and atrioventricular
grooves.
The right coronary artery arises from the anterior aortic sinus and passes
forwards between the pulmonary trunk and the right atrium to descend in
the right part of the atrioventricular groove. At the inferior border of the
heart it continues along the atrioventricular groove to anastomose with the
left coronary at the posterior interventricular groove. It gives off a marginal
branch along the lower border of the heart and the posterior interventricular
branch which runs forward in the inferior interventricular groove and to
anastomose near the apex of the heart with the corresponding branch of the
left coronary artery.
The mediastinum
33
Fig. 26◊The interior of the left ventricle.
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The left coronary artery, which is larger than the right, rises from the left
posterior aortic sinus. Passing first behind and then to the left of the pul-
monary trunk, it reaches the left part of atrioventricular groove in which it
runs laterally round the left border of the heart as the circumflex artery to
reach the posterior interatrial groove. Its most important branch, given off
about 2 cm from its origin, is the anterior interventricular artery which sup-
plies the anterior aspect of both ventricles and passes around the apex of
the heart to anastomose with the posterior interventricular branch of the
right coronary. Note that the sinuatrial node is usually supplied by the right
coronary artery, although the left coronary artery takes over this duty in
about one-third of subjects.
Although anastomoses occur between the terminations of the right and
left coronary arteries, these are usually inefficient. Thrombosis in one or
other of these vessels leads to death of the area of heart muscle supplied (a
myocardial infarction).
The venous drainage of the heart (Fig. 28)
The bulk of the venous drainage of the heart is achieved by veins which
accompany the coronary arteries and which open into the right atrium. The
rest of the blood drains by means of small veins (venae cordis minimae)
directly into the cardiac cavity.
The coronary sinus lies in the posterior atrioventricular groove and
opens into the right atrium just to the left of the mouth of the inferior vena
cava.
It receives:
1◊◊the great cardiac vein in the anterior interventricular groove;
2◊◊the middle cardiac vein the inferior interventricular groove;
3◊◊the small cardiac vein — accompanying the marginal artery along the
lower border of the heart;
34 The Thorax
Fig. 27◊The coronary
arteries. (Dotted vessels
lie posteriorly.)
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4◊◊the oblique vein — descends obliquely on the posterior aspect of the left
atrium.
The anterior cardiac veins (up to three or four in number) cross the ante-
rior atrioventricular groove, drain much of the anterior surface of the heart
and open directly into the right atrium.
Nerve supply
The nerve supply of the heart is derived from the vagus (cardio-inhibitor)
and the cervical and upper 5 thoracic sympathetic ganglia (cardio-
accelerator) by way of superficial and deep cardiac plexuses.
The development of the heart
The primitive heart is a single tube which soon shows grooves demarcating
the sinus venosus, atrium, ventricle and bulbus cordis from behind forwards.
As this tube enlarges it kinks so that its caudal end, receiving venous blood,
comes to lie behind its cephalic end with its emerging arteries (Fig. 29).
The sinus venosus later absorbs into the atrium and the bulbus becomes
incorporated into the ventricle so that, in the fully developed heart, the
atria and great veins come to lie posterior to the ventricles and the roots of
the great arteries.
The boundary tissue between the primitive single atrial cavity
and single ventricle grows out as a dorsal and a ventral endocardial cushion
which meet in the midline, thus dividing the common atrio-ventricular
orifice into a right (tricuspid) and left (mitral) orifice.
The division of the primitive atrium into two is a complicated process
but an important one in the understanding of congenital septal defects
(Fig. 30). A partition, the septum primum, grows downwards from the poste-
rior and superior walls of the primitive common atrium to fuse with the
The mediastinum
35
Fig. 28◊The coronary veins. (Dotted vessels lie posteriorly.)
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endocardial cushions. Before fusion is complete, however, a hole appears in
the upper part of this septum which is termed the foramen secundum in the
septum primum.
A second membrane, the septum secundum, then develops to the right of
the primum but this is never complete; it has a free lower edge which does,
36 The Thorax
Fig. 29◊The coiling of the
primitive heart tube into
its definitive form.
Fig. 30◊The development of the chambers of the heart. (Note the septum primum
and septum secundum which form the interatrial septum, leaving the foramen
ovale as a valve-like opening passing between them.)
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however, extend low enough for this new septum to overlap the foramen
secundum in the septum primum and hence to close it.
The two overlapping defects in the septa form the valve-like foramen
ovale which shunts blood from the right to left heart in the fetus (see ‘fetal
circulation’ below). After birth, this foramen usually becomes completely
fused leaving only the fossa ovalis on the septal wall of the right atrium as
its memorial. In about 10% of adult subjects, however, a probe can still be
insinuated through an anatomically patent, although functionally sealed
foramen.
Division of the ventricle is commenced by the upgrowth of a fleshy
septum from the apex of the heart towards the endocardial cushions. This
stops short of dividing the ventricle completely and thus it has an upper
free border, forming a temporary interventricular foramen. At the same
time, the single truncus arteriosus is divided into aorta and pulmonary
trunk by a spiral septum (hence the spiral relations of these two vessels),
which grows downwards to the ventricle and fuses accurately with the
upper free border of the ventricular septum. This contributes the small pars
membranacea septi, which completes the separation of the ventricle in such a
way that blood on the left of the septum flows into the aorta and on the right
into the pulmonary trunk.
The primitive sinus venosus absorbs into the right atrium so that the
venae cavae draining into the sinus come to open separately into this
atrium. The smooth-walled part of the adult atrium represents the contri-
bution of the sinus venosus, the pectinate part represents the portion
derived from the primitive atrium.
Rather similarly, the adult left atrium has a double origin. The original
single pulmonary venous trunk entering the left atrium becomes absorbed
into it, and donates the smooth-walled part of this chamber with the pul-
monary veins entering as four separate openings; the trabeculated part of
the definitive left atrium is the remains of the original atrial wall.
The development of the aortic arches
and their derivatives (Fig. 31)
Emerging from the bulbus cordis is a common arterial trunk termed the
truncus arteriosus, from which arise six pairs of aortic arches, equivalent to
the arteries supplying the gill clefts of the fish. These arteries curve dorsally
around the pharynx on either side and join to form two longitudinally
placed dorsal aortae which fuse distally into the descending aorta.
The 1st and 2nd arches disappear; the 3rd arches become the
carotids. The 4th arch on the right becomes the brachiocephalic and right
subclavian artery; on the left, it differentiates into the definitive aortic arch,
gives off the left subclavian artery and links up distally with the descending
aorta.
The 5th arch artery is rudimentary and disappears.
When the truncus arteriosus splits longitudinally to form the ascending
aorta and pulmonary trunk, the 6th arch, unlike the others, remains linked
with the latter and forms the right and left pulmonary arteries. On the left
The mediastinum
37
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side this arch retains its connection with the dorsal aorta to form the ductus
arteriosus (the ligamentum arteriosum of adult anatomy).
This asymmetrical development of the aortic arches accounts for the
different course taken by the recurrent laryngeal nerve on each side. In the
early fetus the vagus nerve lies lateral to the primitive pharynx, separated
from it by the aortic arches. What are to become the recurrent laryngeal
nerves pass medially, caudal to the aortic arches, to supply the developing
larynx. With elongation of the neck and caudal migration of the heart, the
recurrent nerves are caught up and dragged down by the descending aortic
arches. On the right side the 5th and distal part of the 6th arch absorb,
leaving the nerve to hook round the 4th arch (i.e. the right subclavian
artery). On the left side, the nerve remains looped around the persisting
distal part the 6th arch (the ligamentum arteriosum) which is overlapped
and dwarfed by the arch of the aorta.
The fetal circulation (Fig. 32)
The circulation of the blood in the embryo is a remarkable example of
economy in nature and results in the shunting of well-oxygenated blood
from the placenta to the brain and the heart, leaving relatively desaturated
blood for less essential structures.
Blood is returned from the placenta by the umbilical vein to the inferior
vena cava and thence the right atrium, most of it by-passing the liver in the
38 The Thorax
Fig. 31◊The aortic arches
and their derivatives.
This diagram explains
the relationship of the
right recurrent laryngeal
nerve to the right
subclavian artery and the
left nerve to the aortic
arch and the ligamentum
arteriosum (or to a patent
ductus arteriosus).
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ductus venosus (see page 95). Relatively little mixing of oxygenated and
deoxygenated blood occurs in the right atrium since the valve overlying the
orifice of the inferior vena cava serves to direct the flow of oxygenated
blood from that vessel through the foramen ovale into the left atrium, while
the deoxygenated stream from the superior vena cava is directed through
the tricuspid valve into the right ventricle. From the left atrium the oxy-
genated blood (together with a small amount of deoxygenated blood from
the lungs) passes into the left ventricle and hence into the ascending aorta
for the supply of the brain and heart via the vertebral, carotid and coronary
arteries.
As the lungs of the fetus are inactive, most of the deoxygenated blood
from the right ventricle is short-circuited by way of the ductus arteriosus
from the pulmonary trunk into the descending aorta. This blood supplies
the abdominal viscera and the lower limbs and is shunted to the placenta,
for oxygenation, along the umbilical arteries arising from the internal iliac
arteries.
At birth, expansion of the lungs leads to an increased blood flow in the
pulmonary arteries; the resulting pressure changes in the two atria bring
the overlapping septum primum and septum secundum into apposition which
effectively closes off the foramen ovale. At the same time active contraction
of the muscular wall of the ductus arteriosus results in a functional closure
The mediastinum
39
Left common
carotid artery
Left subclavian
artery
Ductus arteriosus
Left pulmonary
artery
Pulmonary trunk
Aorta
Umbilical arteries
Brachiocephalic
artery
Right pulmonary
artery
Aorta
Superior
vena cava
Septum II
Foramen ovale
Septum I
Inferior
vena cava
Fig. 32◊The fetal circulation. The red arrows denote oxygenated blood.
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of this arterial shunt and, in the course of the next 2–3 months, its complete
obliteration. Similarly, ligature of the umbilical cord is followed by throm-
bosis and obliteration of the umbilical vessels.
Congenital abnormalities of the heart and great vessels
The complex development of the heart and major arteries accounts for the
multitude of congenital abnormalities which may affect these structures,
either alone or in combination.
Dextro-rotation of the heart means that this organ and its emerging vessels
lie as a mirror-image to the normal anatomy. It may be associated with
reversal of all the intra-abdominal organs; I have seen a student correctly
diagnose acute appendicitis as the cause of a patient’s severe left iliac fossa
pain because he found that the apex beat of the heart was on the right side!
Septal defects
At birth, the septum primum and septum secundum are forced together,
closing the flap valve of the foramen ovale. Fusion usually takes place
about 3 months after birth. In about 10% of subjects, this fusion may be
incomplete. However, the two septa overlap and this patency of the
foramen ovale is of no functional significance. If the septum secundum is
too short to cover the foramen secundum in the septum primum, an atrial
septal defect persists after the septum primum and septum secundum are
pressed together at birth. This results in an ostium secundum defect, which
allows shunting of blood from the left to the right atrium. This defect lies
high up in the atrial wall and is relatively easy to close surgically. A more
serious atrial septal defect results if the septum primum fails to fuse with
the endocardial cushions. This ostium primum defect lies immediately above
the atrioventricular boundary and may be associated with a defect of the
pars membranacea septi of the ventricular septum. In such a case, the child
is born with both an atrial and ventricular septal defect.
Occasionally the ventricular septal defect is so huge that the ventricles
form a single cavity, giving a trilocular heart.
Congenital pulmonary stenosis may affect the trunk of the pulmonary
artery, its valve or the infundibulum of the right ventricle. If stenosis occurs
in conjunction with a septal defect, the compensatory hypertrophy of the
right ventricle (developed to force blood through the pulmonary obstruc-
tion) develops a sufficiently high pressure to shunt blood through the
defect into the left heart; this mixing of the deoxygenated right heart blood
with the oxygenated left-sided blood results in the child being cyanosed at
birth.
The commonest combination of congenital abnormalities causing
cyanosis is Fallot’s tetralogy (Fig. 33). This results from unequal division of
the truncus arteriosus by the spinal septum, resulting in a stenosed pul-
monary trunk and a wide aorta which overrides the orifices of both the ven-
tricles. The displaced septum is unable to close the interventricular septum,
which results in a ventricular septal defect. Right ventricular hypertrophy
40 The Thorax
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develops as a consequence of the pulmonary stenosis. Cyanosis results
from the shunting of large amounts of unsaturated blood from the right
ventricle through the ventricular septal defect into the left ventricle and
also directly into the aorta.
A persistent ductus arteriosus (Fig. 34a) is a relatively common congenital
defect. If left uncorrected, it causes progressive work hypertrophy of the
left heart and pulmonary hypertension.
Aortic coarctation (Fig. 34b) is thought to be due to an abnormality of the
obliterative process which normally occludes the ductus arteriosus. There
may be an extensive obstruction of the aorta from the left subclavian artery
to the ductus, which is widely patent and maintains the circulation to the
The mediastinum
41
Fig. 33◊The tetralogy of
Fallot.
Fig. 34◊(a) Persistent
ductus arteriosus—
showing its close
relationship to the left
recurrent laryngeal
nerve. (b) Coarctation of
the aorta.
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lower parts of the body; often there are multiple other defects and fre-
quently infants so afflicted die at an early age. More commonly there is a
short segment involved in the region of the ligamentum arteriosum or still
patent ductus. In these cases, circulation to the lower limb is maintained via
collateral arteries around the scapula anastomosing with the intercostal
arteries, and via the link-up between the internal thoracic and inferior epi-
gastric arteries.
Clinically, this circulation may be manifest by enlarged vessels being
palpable around the scapular margins; radiologically, dilatation of the
engorged intercostal arteries results in notching of the inferior borders of
the ribs.
Abnormal development of the primitive aortic arches may result in the
aortic arch being on the right or actually being double. An abnormal right
subclavian artery may arise from the dorsal aorta and pass behind the
oesophagus—a rare cause of difficulty in swallowing (dysphagia lusoria).
Rarely, the division of the truncus into aorta and pulmonary artery is
incomplete, leaving an aorta–pulmonary window, the most unusual congeni-
tal fistula between the two sides of the heart.
The superior mediastinum
This is bounded in front by the manubrium sterni and behind the first four
thoracic vertebrae (Fig. 22). Above, it is in direct continuity with the root of
the neck and below it is continuous with the three compartments of the
inferior mediastinum. Its principal contents are: the great vessels, trachea,
oesophagus, thymus— mainly replaced by fatty tissue in the adult, thoracic
duct, vagi, left recurrent laryngeal nerve and the phrenic nerves (Fig. 17).
The arch of the aorta is directed anteroposteriorly, its three great
branches, the brachiocephalic, left carotid and left subclavian arteries, ascend to
the thoracic inlet, the first two forming a V around the trachea. The brachio-
cephalic veins lie in front of the arteries, the left running almost horizontally
across the superior mediastinum and the right vertically downwards; the
two unite to form the superior vena cava. Posteriorly lies the trachea with the
oesophagus immediately behind it lying against the vertebral column.
The oesophagus
The oesophagus, which is 10in (25cm) long, extends from the level of the
lower border of the cricoid cartilage at the level of the 6th cervical vertebra
to the cardiac orifice of the stomach (Fig. 35).
Course and relations
Cervical
In the neck it commences in the median plane and deviates slightly to the
left as it approaches the thoracic inlet. The trachea and the thyroid gland are
its immediate anterior relations, the 6th and 7th cervical vertebrae and pre-
42 The Thorax
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vertebral fascia are behind it and on either side it is related to the common
carotid arteries and the recurrent laryngeal nerves. On the left side it is also
related to the subclavian artery and the terminal part of the thoracic duct
(Fig. 16).
Thoracic
The thoracic part traverses first the superior and then the posterior medi-
astinum. From being somewhat over to the left, it returns to the midline
at T5 then passes downwards, forwards and to the left to reach the
oesophageal opening in the diaphragm (T10). For convenience, the rela-
tions of this part are given in sequence from above downwards.
Anteriorly, it is crossed by the trachea, the left bronchus (which
The mediastinum
43
Fig. 35◊The oesophagus and its relations.
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constricts it), the pericardium (separating it from the left atrium) and the
diaphragm.
Posteriorly lie the thoracic vertebrae, the thoracic duct, the azygos vein
and its tributaries and, near the diaphragm, the descending aorta.
On the left side it is related to the left subclavian artery, the terminal part
of the aortic arch, the left recurrent laryngeal nerve, the thoracic duct and
the left pleura. In the posterior mediastinum it relates to the descending
thoracic aorta before this passes posteriorly to the oesophagus above the
diaphragm.
On the right side there is the pleura and the azygos vein.
Below the root of the lung the vagi form a plexus on the oesophagus, the
left vagus lying anteriorly, the right posteriorly.
In the abdomen, passing forwards through the opening in the right
crus of the diaphragm, the oesophagus comes to lie in the oesophageal
groove on the posterior surface of the left lobe of the liver, covered by peri-
toneum on its anterior and left aspects. Behind it is the left crus of the
diaphragm.
Structure
The oesophagus is made of:
1◊◊an outer connective tissue sheath of areolar tissue;
2◊◊a muscular layer of external longitudinal and internal circular
fibres which are striated in the upper two-thirds and smooth in the lower
one-third;
3◊◊a submucous layer containing mucous glands;
4◊◊a mucosa of stratified epithelium passing abruptly into the columnar
epithelium of the stomach.
Blood supply is from the inferior thyroid artery, branches of the descend-
ing thoracic aorta and the left gastric artery. The veins from the cervical part
drain into the inferior thyroid veins, from the thoracic portion into the
azygos vein and from the abdominal portion partly into the azygos and
partly into the left gastric veins.
The lymphatic drainage is from a peri-oesophageal lymph plexus into the
posterior mediastinal nodes, which drain both into the supraclavicular
nodes and into nodes around the left gastric vessels. It is not uncommon to
be able to palpate hard, fixed supraclavicular nodes in patients with
advanced oesophageal cancer.
Radiographically, the oesophagus is studied by X-rays taken after a
barium swallow, in which it is seen lying in the retrocardiac space just in
front of the vertebral column. Anteriorly, the normal oesophagus is
indented from above downwards by the three most important structures
that cross it, the arch of the aorta, the left bronchus and the left atrium.
Clinical features
1◊◊For oesophagoscopy, measurements are made from the upper incisor
44 The Thorax
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teeth; the three important levels 7in (17cm), 11in (28cm) and 17in
(43cm) corresponding to the commencement of the oesophagus, the
point at which it is crossed by the left bronchus and its termination
respectively.
2◊◊These three points also indicate the narrowest parts of the oesophagus:
the sites at which, as might be expected, swallowed foreign bodies are most
likely to become impacted and strictures to occur after swallowing corro-
sive fluids.
3◊◊The anastomosis between the azygos (systemic) and left gastric (portal)
venous tributaries in the oesophageal veins is of great importance. In portal
hypertension these veins distend into large collateral channels, oesophageal
varices, which may then rupture with severe haemorrhage (probably as a
result of peptic ulceration of the overlying mucosa).
4◊◊Use is made of the close relationship between the oesophagus and the
left atrium in determining the degree of left atrial enlargement in mitral
stenosis; a barium swallow may show marked backward displacement of
the oesophagus caused by the dilated atrium.
5◊◊The oesophagus is crossed solely by the vena azygos on the right side.
This is therefore the side of election to approach the oesophagus surgically.
Development of the oesophagus
The oesophagus develops from the distal part of the primitive fore-gut.
From the floor of the fore-gut also differentiate the larynx and trachea, first
as a groove (the laryngotracheal groove) which then converts into a tube, a
bud on each side of which develops and ramifies into the lung.
This close relationship between the origins of the oesophagus and
trachea accounts for the relatively common malformation in which the
upper part of the oesophagus ends blindly while the lower part opens
into the lower trachea at the level of T4 (oesophageal atresia with tracheo-
oesophageal fistula). Less commonly, the upper part of the oesophagus opens
into the trachea, or oesophageal atresia occurs without concomitant fistula
into the trachea. Rarely, there is a tracheo-oesophageal fistula without
atresia (Fig. 36).
The thoracic duct (Figs 37, 213)
The cisterna chyli lies between the abdominal aorta and right crus of the
diaphragm. It drains lymphatics from the abdomen and the lower limbs,
then passes upwards through the aortic opening to become the thoracic
duct. This ascends behind the oesophagus, inclines to the left of the oesoph-
agus at the level of T5, then runs upwards behind the carotid sheath,
descends over the subclavian artery and drains into the commencement of
the left brachiocephalic vein (see Fig. 213).
The left jugular, subclavian and mediastinal lymph trunks, draining the left
side of the head and neck, upper limb and thorax respectively, usually join
the thoracic duct, although they may open directly into the adjacent large
veins at the root of the neck.
The mediastinum
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46 The Thorax
Fig. 36◊The usual form of
oesophageal stenosis.
The upper oesophagus
ends blindly; the lower
oesophagus
communicates with the
trachea at the level of the
4th thoracic vertebra.
Left
brachiocephalic
vein
Thoracic
duct
Oesophagus
Superior
vena cava
Azygos
vein
Cisterna
chyli
Left
subclavian
vein
Jugular
Subclavian
lymph
trunk
Fig. 37◊The course of the
thoracic duct.
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The thoracic duct thus usually drains the whole lymphatic field below
the diaphragm and the left half of the lymphatics above it.
On the right side, the right subclavian, jugular and mediastinal trunks
may open independently into the great veins. Usually the subclavian and
jugular trunks first join into a right lymphatic duct and this may be joined by
the mediastinal trunk so that all three then have a common opening into the
origin of the right brachiocephalic vein.
Clinical features
1◊◊The lymphatics may become blocked by infection and fibrosis due to
the Microfilaria bancrofti. This usually results in lymphoedema of the legs
and scrotum but occasional involvement of the main channels of the trunk
and thorax is followed by chylous ascites, chyluria and chylous pleural
effusion.
2◊◊The thoracic duct may be damaged during block dissection of the neck.
If noticed at operation, the injured duct should be ligated; lymph then finds
its way into the venous system by anastomosing channels. If the accident is
missed, there follows an unpleasant chylous fistula in the neck.
3◊◊Tears of the thoracic duct have also been reported as a complication of
fractures of the thoracic vertebrae to which, in its lower part, the duct is
closely related. Such injuries are followed by a chylothorax.
The thoracic sympathetic trunk (Fig. 38)
The sympathetic chain lies immediately lateral to the mediastinum behind
the parietal pleura.
Descending from the cervical chain, it crosses:
•◊◊the neck of the first rib;
•◊◊the heads of the 2nd to 10th ribs;
•◊◊the bodies of the 11th and 12th thoracic vertebrae.
It then passes behind 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 fre-
quently joins the inferior cervical ganglion to form the stellate ganglion. Each
ganglion receives a white ramus communicans containing preganglionic
fibres from its corresponding spinal nerve and donates back a grey ramus,
bearing postganglionic fibres.
Branches
1◊◊Sympathetic fibres are distributed to the skin with each of the thoracic
spinal nerves.
2◊◊Postganglionic fibres from T1–5 are distributed to the thoracic viscera—
the heart and great vessels, the lungs and the oesophagus.
3◊◊Mainly preganglionic fibres from T5–12 form the splanchnic nerves,
which pierce the crura of the diaphragm and pass to the coeliac, superior
The mediastinum
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48 The Thorax
DIAPHRAGM
1s
t R
IB
Trachea
Oesophagus
Thoraic duct
Subclavian A.
Sympathetic
chain
Bronchus
Greater
splanchnic
nerve
Common
cartoid
X
Aortic
arch
Phrenic
nerve
DIAPHRAGM
1st RIB
Oesophagus and
trachea
Vagus and
phrenic
nerves
Azygos
vein
Thoracic sympathetic
ganglion trunk
Bronchus
Contribution
to greater
splanchnic
nerve
Superior
vena cava
R. Pulmonary
A. & V.
Cut edge of
pleura
Inferior
vena cava
(a)
(b)
Fig. 38◊(a) The left
thoracic sympathetic
trunk with a display of
the left mediastinum. (b)
The right mediastinum.
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mesenteric, inferior mesenteric and renal ganglia from which they are
relayed as postganglionic fibres to the abdominal viscera. These splanchnic
nerves are the:
•◊◊greater splanchnic (T5–10);
•◊◊lesser splanchnic (T10–11);
•◊◊least splanchnic (T12).
They lie medial to the sympathetic trunk on the bodies of the thoracic verte-
bra and are quite easily visible through the parietal pleura (For their distrib-
ution see pages 429 and 430).
Clinical features
A high spinal anaesthetic will produce temporary hypotension by
paralysing the sympathetic (vasoconstrictor) preganglionic outflow from
spinal segment T5 downwards, passing to the abdominal viscera.
On the examination of a
chest radiograph
The following features should be examined in every radiograph of
the chest.
Centering and density of film
The sternal ends of the two clavicles should be equidistant from the shadow
of the vertebral spines. The assessment of the density of the film can only be
learned by experience, but in a ‘normal’ film the bony cage should be
clearly outlined and the larger vessels in the lung fields clearly visible.
General shape
Any abnormalities in the general form of the thorax (scoliosis, kyphosis and
the barrel chest of emphysema, for example) should always be noted before
other abnormalities are described.
Bony cage
The thoracic vertebrae should be examined first, then each of the ribs in
turn (counting conveniently from their posterior ends and comparing each
one with its fellow of the opposite side), and finally clavicles and scapulae.
Unless this procedure is carried out systematically, important diagnostic
clues (e.g. the presence of a cervical rib, or notching of the ribs by enlarged
anastomotic vessels) are liable to be missed.
On the examination of a chest radiograph
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The domes of the diaphragm
These should be examined for height and symmetry and the nature of the
cardiophrenic and costophrenic angles observed.
The mediastinum
The outline of the mediastinum should be traced systematically. Special
note should be made of the size of the heart, of mediastinal shift and of the
vessels and nodes at the hilum of the lung.
Lung fields
Again, systematic examination of the lung fields visible in each intercostal
space is necessary if slight differences between the two sides are not to be
overlooked.
Abnormalities
When this scheme has been carefully followed, any abnormalities in the
bony cage, the mediastinum or lung fields should now be apparent. They
should then be defined anatomically as accurately as possible and checked,
where necessary, by reference to a film taken from a different angle.
Radiographic appearance of the heart
For the appearance of the heart as seen at fluoroscopy, reference should be
made to a standard work in radiology or cardiology. In the present account,
only the more important features of the heart and great vessels which can
be seen in standard posteroanterior and oblique lateral radiographs of the
chest will be described.
The heart and great vessels in anteroposterior
radiographs (Fig. 39)
The greater part of the ‘mediastinal shadow’ in an anteroposterior film of
the chest is formed by the heart and great vessels. These should be exam-
ined as follows.
Size and shape of the heart
Normally the transverse diameter should not exceed half the total width of
the chest, but since it varies widely with bodily build and the position of the
heart, these factors must also be assessed. The shape of the cardiac shadow
also varies a good deal with the position of the heart, being long and
narrow in a vertically disposed heart and broad and rounded in the so-
called horizontal heart.
50 The Thorax
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On the examination of a chest radiograph
51
Fig. 39◊A tracing of a chest radiograph to show the composition of the right and left
borders of the mediastinal shadow.
The cardiac outline
Each ‘border’ of the cardiac shadow should be examined in turn. The right
border of the mediastinal shadow is formed from above downwards by the
right brachiocephalic vein, the superior vena cava and the right atrium.
Immediately above the heart, the left border of the mediastinal shadow pre-
sents a well-marked projection, the aortic knuckle, which represents the arch
of the aorta seen ‘end-on’. Beneath this there are, successively, the shadows
due to the pulmonary trunk (or the infundibulum of the right ventricle), the
auricle of the left atrium, and the left ventricle. The shadow of the inferior
border of the heart blends centrally with that of the diaphragm, but on
either side the two shadows are separated by the well-defined cardio-
phrenic angles.
The heart and great vessels in anterior
oblique radiographs
The left oblique view (Fig. 40)
The greater part of the mediastinal shadow in this view is formed
by the right and left ventricles, above which the relation of the arch of the
aorta and the pulmonary trunk to the translucent trachea can be seen.
The right oblique view (Fig. 41)
Almost all of the cardiac shadow in this view is due to the right ventricle. It
is particularly useful for the assessment of the size of the left atrium since its
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