The Relations Of The Principal Bloodvessels To The Viscera Of The Thoracico-abdominal Cavity


Sources: Surgical Anatomy

The median line of the body is occupied by the centres of the four great

systems of organs which serve in the processes of circulation,

respiration, innervation, and nutrition. These organs being fashioned in

accordance with the law of symmetry, we find them arranged in close

connexion with the vertebrate centre of the osseous fabric, which is

itself symmetrical. In this symmetrical arrangement of the main organs

of the trunk of the body, a mechanical principle is prominently

apparent; for as the centre is the least moveable and most protected

region of the form, so have these vitally important structures the full

benefit of this situation. The aortal trunk, G, of the arterial system

is disposed along the median line, as well for its own safety as for the

fitting distribution of those branches which spring symmetrically from

either side of it to supply the lateral regions of the body.



The visceral system of bloodvessels is moulded upon the organs which

they supply. As the thoracic viscera differ in form and functional

character from those of the abdomen, so we find that the arterial

branches which are supplied by the aorta to each set, differ likewise in

some degree. In the accompanying figure, which represents the thoracic

and abdominal visceral branches of the aorta taken in their entirety,

this difference in their arrangement may be readily recognised. In the

thorax, compared with the abdomen, we find that not only do the aortic

branches differ in form according to the variety of those organs

contained in either region, but that they differ numerically according

to the number of organs situated in each. The main vessel itself,

however, is common to both regions. It is the one thoracico-abdominal

vessel, and this circumstance calls for the comparison, not only of the

several parts of the great vessel itself, but of all the branches which

spring from it, and of the various organs which lie in its vicinity in

the thorax and abdomen, and hence we are invited to the study of these

regions themselves connectedly.



In the thorax, the aorta, G G*, is wholly concealed by the lungs in

their states both of inspiration and expiration. The first part of the

aortic arch, as it springs from the left ventricle of the heart, is the

most superficial, being almost immediately sub-sternal, and on a level

with the sternal junctions of the fourth ribs. By applying the ear at

this locality, the play of the aortic valves may be distinctly heard.

From this point the aorta, G, rises and arches from before, backwards,

to the left side of the spine, G*. The arch of the vessel lies more

deeply between the two lungs than does its ventricular origin. The

descending thoracic aorta lies still more deeply situated at the left

side of the dorsal spine. At this latter situation it is in immediate

contact with the posterior thick part of the left lung; whilst on its

right are placed, L, the thoracic duct; I, the oesophagus; K, the vena

azygos, and the vertebral column. In Plate 26 may be seen the relation

which the superior vena cava, H, bears to the aortic arch, A.



In the span of the aortic arch will be found, H*, the left bronchus,

together with the right branch of the pulmonary artery, and the right

pulmonary veins. The pneumo-gastric and phrenic nerves descend on either

side of the arch. The left pneumo-gastric nerve winds round beneath the

arch at the point where the obliterated ductus arteriosus joins it. See

Plates 12 & 26.



The pulmonary artery, B, Plates 1 & 2, lies close upon the fore part,

and conceals the origin, of the systemic aorta. Whenever, therefore, the

semilunar valves of either the pulmonary artery or the systemic aorta

become diseased, it must be extremely difficult to distinguish by the

sounds alone, during life, in which of the two the derangement exists.

The origins of both vessels being at the fore part of the chest, it is

in this situation, of course, that the state of their valves is to be

examined. The descending part of the thoracic aorta, G*, being at the

posterior part of the chest, and lying on the vertebral ends of the left

thoracic ribs, will therefore require that we should examine its

condition in the living body at the dorsal aspect of the thorax. As the

arch of the aorta is directed from before backwards--that is, from the

sternum to the spine, it follows that when an aneurism implicates this

region of the vessel, the exact situation of the tumour must be

determined by antero-posterior examination; and we should recollect,

that though on the fore part of the chest the cartilages of the second

ribs, where these join the sternum, mark the level of the aortic arch,

on the back of the chest its level is to be taken from the vertebral

ends of the third or fourth ribs. This difference is caused by the

oblique descent of the ribs from the spine to the sternum. The first and

second dorsal vertebrae, with which the first and second ribs

articulate, are considerably above the level of the first and second

pieces of the sternum.



In a practical point of view, the pulmonary artery possesses but small

interest for us; and in truth the trunk of the systemic aorta itself may

be regarded in the same disheartening consideration, forasmuch as when

serious disease attacks either vessel, the "tree of life" may be said to

be lopped at its root.



When an aneurism arises from the aortic arch it implicates those

important organs which are gathered together in contact with itself. The

aneurismal tumour may press upon and obstruct the bronchi, H H*; the

thoracic duct, L; the oesophagus, I; the superior vena cava, H, Plate

26, or wholly obliterate either of the vagi nerves. The aneurism of the

arch of the aorta may cause suffocation in two ways--viz., either by

pressing directly on the tracheal tube, or by compressing and irritating

the vagus nerve, whose recurrent branch will convey the stimulus to the

laryngeal muscles, and cause spasmodic closure of the glottis. This

anatomical fact also fully accounts for the constant cough which attends

some forms of aortic aneurism. The pulmonary arteries and veins are also

liable to obstruction from the tumour. This will occur the more

certainly if the aneurism spring from the right or the inferior side of

the arch, and if the tumour should not break at an early period, slow

absorption, caused by pressure of the tumour, may destroy even the

vertebral column, and endanger the spinal nervous centre. If the tumour

spring from the left side or the fore part of the arch, it may in time

force a passage through the anterior wall of the thorax.



The principal branches of the thoracic aorta spring from the upper part

of its arch. The innominate artery, 2, is the first to arise from it;

the left common carotid, 6, and the left subclavian artery, 5, spring in

succession. These vessels being destined for the head and upper limbs,

we find that the remaining branches of the thoracic aorta are

comparatively diminutive, and of little surgical interest. The

intercostal arteries occasionally, when wounded, call for the aid of the

surgeon; these arteries, like all other branches of the aorta, are

largest at their origin. Where these vessels spring from G, the

descending thoracic aorta, they present considerable caliber; but at

this inaccessible situation, they seldom or never call for surgical

interference. As the intercostal arteries pass outwards, traversing the

intercostal spaces with their accompanying nerves, they diminish in

size. Each vessel divides at a distance of about two inches, more or

less, from the spine; and the upper larger branch lies under cover of

the inferior border of the adjacent rib. When it is required to perform

the operation of paracentesis thoracis, this distribution of the vessel

should be borne in mind; and also, that the farther from the spine this

operation is performed, the less in size will the vessels be found. The

intercostal artery is sometimes wounded by the fractured end of the rib,

in which case, if the pleura be lacerated, an effusion of blood takes

place within the thorax, compresses the lung, and obstructs respiration.



The thoracic aorta descends along the left side of the spine, as far as

the last dorsal vertebra, at which situation the pillars of the

diaphragm overarch the vessel. From this place the aorta passes

obliquely in front of the five lumbar vertebrae, and on arriving

opposite the fourth, it divides into the two common iliac branches. The

aorta, for an extent included between these latter boundaries, is named

the abdominal aorta, and from its fore part arise those branches, which

supply the viscera of the abdomen.



The branches which spring from the abdominal aorta to supply the viscera

of this region, are considerable, both as to their number and size. They

are, however, of comparatively little interest in practice. To the

anatomist they present many peculiarities of distribution and form

worthy of notice, as, for example, their frequent anastomosis, their

looping arrangement, and their large size and number compared with the

actual bulk of the organs which they supply. As to this latter

peculiarity, we interpret it according to the fact that here the vessels

serve other purposes in the economy besides that of the support and

repair of structure. The vessels are large in proportion to the great

quantity of fluid matter secreted from the whole extent of the inner

surface of this glandular apparatus--the gastro-intestinal canal, the

liver, pancreas, and kidneys.



As anatomists, we are enabled, from a knowledge of the relative position

of the various organs and bloodvessels of both the thorax and abdomen,

to account for certain pathological phenomena which, as practitioners,

we possess as yet but little skill to remedy. Thus it would appear most

probable that many cases of anasarca of the lower limbs, and of dropsy

of the belly, are frequently caused by diseased growths of the liver, P,

obstructing the inferior vena cava, R, and vena portae, rather than by

what we are taught to be the "want of balance between secreting and

absorbing surfaces." The like occurrence may obstruct the gall-ducts,

and occasion jaundice. Over-distention of any of those organs situated

beneath the right hypochondrium, will obstruct neighbouring organs and

vessels. Mechanical obstruction is doubtless so frequent a source of

derangement, that we need not on many occasions essay a deeper search

for explaining the mystery of disease.



In the right hypochondriac region there exists a greater variety of

organs than in the left; and disease is also more frequent on the right

side. Affections of the liver will consequently implicate a greater

number of organs than affections of the spleen on the left side, for the

spleen is comparatively isolated from the more important blood vessels

and other organs.



The external surface of the liver, P, lies in contact with the

diaphragm, N, the costal cartilages, M, and the upper and lateral parts

of the abdominal parietes; and when the liver becomes the seat of

abscess, this, according to its situation, will point and burst either

into the thorax above, or through the side between or beneath the false

ribs, M. The hepatic abscess has been known to discharge itself through

the stomach, the duodenum, T, and the transverse colon, facts which are

readily explained on seeing the close relationship which these parts

hold to the under surface of the liver. When the liver is inflamed, we

account for the gastric irritation, either from the inflammation having

extended to the neighbouring stomach, or by this latter organ being

affected by "reflex action." The hepatic cough is caused by the like

phenomena disturbing the diaphragm, N, with which the liver, P, lies in

close contact.



When large biliary concretions form in S, the gallbladder, or in the

hepatic duct, Nature, failing in her efforts to discharge them through

the common bile-duct, into the duodenum, T, sets up inflammation and

ulcerative absorption, by aid of which processes they make a passage for

themselves through some adjacent part of the intestine, either the

duodenum or the transverse colon. In these processes the gall-bladder,

which contains the calculus, becomes soldered by effused lymph to the

neighbouring part of the intestinal tube, into which the stone is to be

discharged, and thus its escape into the peritoneal sac is prevented.

When the hepatic abscess points externally towards M, the like process

isolates the matter from the cavities of the chest and abdomen.



In wounds of any part of the intestine, whether of X, the caecum, W, the

sigmoid flexure of the colon, or Z, the small bowel, if sufficient time

be allowed for Nature to establish the adhesive inflammation, she does

so, and thus fortifies the peritoneal sac against an escape of the

intestinal matter into it by soldering the orifice of the wounded

intestine to the external opening. In this mode is formed the artificial

anus. The surgeon on principle aids Nature in attaining this result.





DESCRIPTION OF PLATE 24.



A. The thyroid body.



B. The trachea.



C C*. The first ribs.



D D*. The clavicles, cut at their middle.



E. Humeral part of the great pectoral muscle, cut.



F. The coracoid process of the scapula.



G. The arch of the aorta. G*. Descending aorta in the thorax.



H. Right bronchus. H*. Left bronchus.



I. Oesophagus.



K. Vena azygos receiving the intercostal veins.



L. Thoracic duct.



M M*. Seventh ribs.



N N. The diaphragm, in section.



O. The cardiac orifice of the stomach.



P. The liver, in section, showing the patent orifices of the hepatic

veins.



Q. The coeliac axis sending off branches to the liver, stomach, and

spleen. The stomach has been removed, to show the looping anastomosis

of these vessels around the superior and inferior borders of the stomach.



R. The inferior vena cava about to enter its notch in the posterior

thick part of the liver, to receive the hepatic veins.



S. The gall-bladder, communicating by its duct with the hepatic duct,

which is lying upon the vena portae, and by the side of the hepatic

artery.



T. The pyloric end of the stomach, joining T*, the duodenum.



U. The spleen.



V V. The pancreas.



W. The sigmoid flexure of the colon.



X. The caput coli.



Y. The mesentery supporting the numerous looping branches of the

superior mesenteric artery.



Z. Some coils of the small intestine.



2. Innominate artery.



3. Right subclavian artery.



4. Right common carotid artery.



5. Left subclavian artery.



6. Left common carotid artery.



7. Left axillary artery.



8. Coracoid attachment of the smaller pectoral muscle.



9. Subscapular muscle.



10. Coracoid head of the biceps muscle.



11. Tendon of the latissimus dorsi muscle.



12. Superior mesenteric artery, with its accompanying vein.



13. Left kidney.





Chest and abdomen, showing bones, blood vessels, muscles<br />
<br />
and other internal organs






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