The Relative Position Of The Superficial Organs Of The Thorax And Abdomen

Sources: Surgical Anatomy

In the osseous skeleton, the thorax and abdomen constitute a common

compartment. We cannot, while we contemplate this skeleton, isolate the

one region from the other by fact or fancy. The only difference which I

can discover between the regions called thorax and abdomen, in the

osseous skeleton, (considering this body morphologically,) results,

simply, from the circumstance that the ribs, which enclose thoracic

space, ave no osseous counterparts in the abdomen enclosing abdominal

space, and this difference is merely histological. In man and the

mammalia the costal arches hold relation with the pulmonary organs, and

these costae fail at that region where the ventral organs are located.

In birds, and many reptiles, the costal arches enclose the common

thoracico-abdominal region, as if it were a common pulmonary region. In

fishes the costal arches enclose the thoracico-abdominal region, just as

if it were a common abdominal region. I merely mention these general

facts to show that costal enclosure does not actually serve to isolate

the thorax from the abdomen in the lower classes of animals; and on

turning to the human form, I find that this line of separation between

the two compartments is so very indefinite, that, as pathologists, we

are very liable to err in our diagnosis between the diseased and the

healthy organs of either region, as they lie in relation with the

moveable diaphragm or septum in the living body. The contents of the

whole trunk of the body from the top of the sternum to the perineum are

influenced by the respiratory motions; and it is most true that the

diaphragmatic line, H F H*, is alternately occupied by those organs

situated immediately above and below it during the performance of these

motions, even in health.



The organs of the thoracic region hold a certain relation to each other

and to the thoracic walls. The organs of the abdomen hold likewise a

certain relation to each other and to the abdominal parietes. The organs

of both the thorax and the abdomen have a certain relation to each

other, as they lie above and below the diaphragm. In dead nature these

relations are fixed and readily ascertainable, but in living, moving

nature, the organs influence this relative position, not only of each

other, but also of that which they bear to the cavities in which they

are contained. This change of place among the organs occurs in the

normal or healthy state of the living body, and, doubtless, raises some

difficulty in the way of our ascertaining, with mathematical precision,

the actual state of the parts which we question, by the physical signs

of percussion and auscultation. In disease this change of place among

these organs is increased, and the difficulty of making a correct

diagnosis is increased also in the same ratio. For when an emphysematous

lung shall fully occupy the right thoracic side from B to L, then G, the

liver, will protrude considerably into the abdomen beneath the right

asternal ribs, and yet will not be therefore proof positive that the

liver is diseased and abnormally enlarged. Whereas, on the other hand,

when G, the liver, is actually diseased, it may occupy a situation in

the right side as high as the fifth or sixth ribs, pushing the right

lung upwards as high as that level; and, therefore, while percussion

elicits a dull sound over this place thus occupied, such sound will not

be owing to a hepatized lung, but to the absence of the lung caused by

the presence of the liver.



In the healthy adult male body, Plate 22, the two lungs, D D*, whilst in

their ordinary expanded state, may be said to range over all that region

of the trunk of the body which is marked by the sternal and asternal

ribs. The heart, E, occupies the thoracic centre, and part of the left

thoracic side. The heart is almost completely enveloped in the two

lungs. The only portion of the heart and pericardium, which appears

uncovered by the lung on opening the thorax, is the base of the right

ventricle, E, situated immediately behind the lower end of the sternum,

where this bone is joined by the cartilages of the sixth and seventh

ribs. The lungs range perpendicularly from points an inch above B, the

first rib, downwards to L, the tenth rib, and obliquely downwards and

backwards to the vertebral ends of the last ribs. This space varies in

capacity, according to the degree in which the lungs are expanded within

it. The increase in thoracic space is attained, laterally, by the

expansion of the ribs, C I; and vertically, by the descent of the

diaphragm, H, which forces downwards the mass of abdominal viscera. The

contraction of thoracic space is caused by the approximation of all the

ribs on each side to each other; and by the ascent of the diaphragm. The

expansion of the lungs around the heart would compress this organ, were

it not that the costal sides yield laterally while the diaphragm itself

descends. The heart follows the ascent and descent of the diaphragm,

both in ordinary and forced respiration.



But however much the lungs vary in capacity, or the heart as to position

in the respiratory motions, still the lungs are always closely applied

to the thoracic walls. Between the pleura costalis and pulmonalis there

occurs no interval in health. The thoracic parietes expand and contract

to a certain degree; and to that same degree, and no further, do the

lungs within the thorax expand and contract. By no effort of expiration

can the animal expel all the air completely from its lungs, since by no

effort of its own, can it contract thoracic space beyond the natural

limit. On the other hand, the utmost degree of expansion of which the

lungs are capable, exactly equals that degree in which the thoracic

walls are dilatable by the muscular effort; and, therefore, between the

extremes of inspiration and expiration, the lungs still hold closely

applied to the costal parietes. The air within the lungs is separated

from the air external to the thorax, by the thoracic parietes. The air

within and external to the lungs communicate at the open glottis. When

the glottis closes and cuts off the communication, the respiratory act

ceases--the lungs become immovable, and the thoracic walls are (so far

as the motions of respiration are concerned) rendered immovable also.

The muscles of respiration cannot, therefore, produce a vacuum between

the pulmonic and costal pleura, either while the external air has or has

not access to the lungs. Upon this fact the mechanism of respiration

mainly depends; and we may see a still further proof of this in the

circumstance that, when the thoracic parietes are pierced, so as to let

the external air into the cavity of the pleura, the lung collapses and

the thoracic side ceases to exert an expansile influence over the lung.

When in cases of fracture of the rib the lung is wounded, and the air of

the lung enters the pleura, the same effect is produced as when the

external air was admitted through an opening in the side.



When serous or purulent effusion takes place within the cavity of the

pleura, the capacity of the lung becomes lessened according to the

quantity of the effusion. It is more reasonable to expect that the soft

tissue of the lung should yield to the quantity of fluid within the

pleural cavity, than that the rigid costal walls should give way

outwardly; and, therefore, it seldom happens that the practitioner can

discover by the eye any strongly-marked difference between the thoracic

walls externally, even when a considerable quantity of either serum,

pus, or air, occupies the pleural sacs.



In the healthy state of the thoracic organs, a sound characteristic of

the presence of the lung adjacent to the walls of the thorax may be

elicited by percussion, or heard during the respiratory act through the

stethoscope, over all that costal space ranging anteriorly between B,

the first rib, and I K, the eight and ninth ribs. The respiratory murmur

can be heard below the level of these ribs posteriorly, for the lung

descends behind the arching diaphragm as far as the eleventh rib.



When fluid is effused into the pleural cavity, the ribs are not moved by

the intercostal muscles opposite the place occupied by the fluid, for

this has separated the lung from the ribs. The fluid has compressed the

lung; and in the same ratio as the lung is prevented from expanding, the

ribs become less moveable. The presence of fluid in the pleural sac is

discoverable by dulness on percussion, and, as might be expected, by the

absence of the respiratory murmur at that locality which the fluid

occupies. Fluid, when effused into the pleural sac, will of course

gravitate; and its position will vary according to the position of the

patient. The sitting or standing posture will therefore suit best for

the examination of the thorax in reference to the presence of fluid.



Though the lungs are closely applied to the costal sides at all times in

the healthy state of these organs, still they slide freely within the

thorax during the respiratory motions--forwards and backwards--over the

serous pericardium, E, and upwards and downwards along the pleura

costalis. The length of the adhesions which supervene upon pleuritis

gives evidence of the extent of these motions. When the lung becomes in

part solidified and impervious to the inspired air, the motions of the

thoracic parietes opposite to the part are impeded. Between a solidified

lung and one which happens to be compressed by effused fluid it requires

no small experience to distinguish a difference, either by percussion or

the use of the stethoscope. It is great experience alone that can

diagnose hydro-pericardium from hypertrophy of the substance of the

heart by either of these means.



The thoracic viscera gravitate according to the position of the body.

The heart in its pericardial envelope sways to either side of the

sternal median line according as the body lies on this or that side. The

two lungs must, therefore, be alternately affected as to their capacity

according as the heart occupies space on either side of the thorax. In

expiration, the heart, E, is more uncovered by the shelving edges of the

lungs than in inspiration. In pneumothorax of either of the pleural sacs

the air compresses the lung, pushes the heart from its normal position,

and the space which the air occupies in the pleura yields a clear hollow

sound on percussion, whilst, by the ear or stethoscope applied to a

corresponding part of the thoracic walls, we discover the absence of the

respiratory murmur.



The transverse diameter of the thoracic cavity varies at different

levels from above downwards. The diameter which the two first ribs, B

B*, measure, is the least. That which is measured by the two eighth

ribs, I I*, is the greatest. The perpendicular depth of the thorax,

measured anteriorly, ranges from A, the top of the sternum, to F, the

xyphoid cartilage. Posteriorly, the perpendicular range of the thoracic

cavity measures from the spinous process of the seventh cervical

vertebra above, to the last dorsal spinous process below. In full,

deep-drawn inspiration in the healthy adult, the ear applied to the

thoracic walls discovers the respiratory murmur over all the space

included within the above mentioned bounds. After extreme expiration, if

the thoracic walls be percussed, this capacity will be found much

diminished; and the extreme limits of the thoracic space, which during

full inspiration yielded a clear sound, indicative of the presence of

the lung, will now, on percussion, manifest a dull sound, in consequence

of the absence of the lung, which has receded from the place previously

occupied.



Owing to the conical form of the thoracic space, the apex of which is

measured by the first ribs, B B*, and the basis by I I*, it will be seen

that if percussion be made directly from before, backwards, over the

pectoral masses, R R*, the pulmonic resonance will not be elicited. When

we raise the arms from the side and percuss the thorax between the folds

of the axillae, where the serratus magnus muscle alone intervenes

between the ribs and the skin, the pulmonic sound will answer clearly.



At the hypochondriac angles formed between the points F, L, N, on either

side the lungs are absent both in inspiration and expiration.

Percussion, when made over the surface of the angle of the right side,

discovers the presence of the liver, G G*. When made over the median

line, and on either side of it above the umbilicus, N, we ascertain the

presence of the stomach, M M*. In the left hypochondriac angle, the

stomach may also be found to occupy this place wholly.



Beneath the umbilicus, N, and on either side of it as far outwards as

the lower asternal ribs, K L, thus ranging the abdominal parietes

transversely, percussion discovers the transverse colon, O, P, O*. The

small intestines, S S*, covered by the omentum, P*, occupy the

hypogastric and iliac regions.



The organs situated within the thorax give evidence that they are

developed in accordance to the law of symmetry. The lungs form a pair,

one placed on either side of the median line. The heart is a double

organ, formed of the right and left heart. The right lung differs from

the left, inasmuch as we find the former divided into three lobes, while

the latter has only two. That place which the heart now occupies in the

left thoracic side is the place where the third or middle lobe of the

left lung is wanting. In the abdomen we find that most of its organs are

single. The liver, stomach, spleen, colon, and small intestine form a

series of single organs: each of these may be cleft symmetrically. The

kidneys are a pair.



The extent to which the ribs are bared in the figure Plate 22, marks

exactly the form and transverse capacity of the thoracic walls. The

diaphragm, H H*, has had a portion of its forepart cut off, to show how

it separates the thin edges of both lungs above from the liver, G, and

the stomach, M, below. These latter organs, although occupying abdominal

space, rise to a considerable height behind K L, the asternal ribs, a

fact which should be borne in mind when percussing the walls of the

thorax and abdomen at this region.





DESCRIPTION OF PLATE 22.



A. Upper bone of the sternum.



B B*. Two first ribs.



C C*. Second pair of ribs.



D D*. Right and left lungs.



E. Pericardium, enveloping the heart--the right ventricle.



F. Lower end of the sternum.



G G*. Lobes of the liver.



H H*. Right and left halves of the diaphragm in section. The right half

separating the right lung from the liver; the left half separating

the left lung from the broad cardiac end of the stomach.



I I*. Eighth pair of ribs.



K K*. Ninth pair of ribs.



L L*. Tenth pair of ribs.



M M*. The stomach; M, its cardiac bulge; M*, its pyloric extremity.



N. The umbilicus.



OO*. The transverse colon.



P P*. The omentum, covering the transverse colon and small intestines.



Q. The gall bladder.



R R*. The right and left pectoral prominences.



S S*. Small intestines.