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which the liver is composed. Each lobule is a small irregular or polygonal area, measuring from th to th of an inch in diameter, or 1 to 2 mm., with a partial covering of fine connective tissue, forming a delicate stroma.
In the adult, the liver weighs from 3 to 3 pounds, or about th of the body weight, and it is somewhat heavier in the male than in the female, its weight in the former being from 50 to 55 ounces and in the latter 43 to 48 ounces. The ratio to the body weight is the same in both sexes. In the foetus and child it is relatively very large and heavy. At birth it occupies the greater part of the abdominal cavity, and constitutes from th to th of the body weight. In the young foetus the ratio is even larger.
The average size of the liver may be briefly expressed as follows:-It measures in the transverse direction about seven inches (17.5 cm.); in the vertical, six to seven inches (15 to 175 cm.); and in the antero-posterior, on the right side where greatest, about six inches (15 cm.). Its
greatest width, measured obliquely from side to side along the inferior or visceral surface, is ten inches (25 cm.).
The liver is capable of being greatly distended by fluid forced into its blood-vessels. It surface then becomes tense, and the consistence of the whole organ becomes much firmer.
Shape. If the liver is hardened in situ and then removed from the body, it will be found to present a form which is fairly constant, but which is modified by the shape and size of the adjacent viscera, and hence shows minor variations in different individuals.
If the liver has not been hardened, it does not retain, after removal, the shape and form which it had when it lay in the abdomen, but tends to collapse inte a flattened cake-like mass.
The description of the shape, surfaces, and borders given below is drawn from examination of specimens hardened in situ.
The liver possesses three principal surfaces, a superior, a posterior and inferior or visceral.
The facies superior is in contact chiefly with the rounded vault of the abdomina cavity, and hence it is uniformly rounded and convex.
The facies posterior, directed backwards, is in contact with the structure
forming the superior portion of the posterior abdominal wall. It is deeply indented by the projecting vertebral column, and it is nearly flat in the vertical axis.
The facies inferior is directed obliquely downwards and posteriorly, is in contact with a number of the abdominal viscera, especially the right kidney, stomach, duodenum, and colon, and its general configuration is influenced to a marked degree by the shape and position of these organs.
This surface is sometimes termed the visceral, in contrast to the other surfaces, which constitute the parietal surface of the organ.
The parietal and visceral surfaces are marked off from one another by the inferior margin of the liver. Posteriorly, this margin is indistinctly marked and corresponds to the inferior edge of the posterior area, or back, of the parietal surface: it is in contact with the right kidney, and lies along the course of the eleventh rib. At the right side the margin is stout but distinct, and usually corresponds to, or projects a little way below, the inferior border of the thoracic
framework. Anteriorly, the border is thin and sharp, and passes obliquely upwards from the right to the left side behind the anterior abdominal wall. This portion forms the margo anterior. Its direction corresponds to a line drawn from a point half an inch (12 mm.) below the margin of the ribs (tip of tenth costal cartilage) on the right side to a point an inch below the nipple on the left. It extends down in the median plane to a point half-way between the body of the sternum and the umbilicus. This portion of the lower border usually, but not invariably, presents one or two notches. The incisura umbilicalis, the more constant of the two (Fig. 936), is situated at the anterior end of a cleft on the inferior surface, known as the fossa sagittalis sinistra (see p. 1191), and corresponds to the upper part of the ligamentum teres hepatis. It is usually placed from one to two inches (2.5 to 50 cm.) to the right of the median plane. The second notch, less frequently present, corresponds to the fundus of the gall-bladder, and is called the incisura vesicæ felleæ.
At its left extremity the margo anterior turns posteriorly round the edge of the left lobe, and ends at a groove on the posterior surface, termed the impressio œsophagea, in which the oesophagus lies.
The division between the superior surface and the posterior surface is not marked by a border of any prominence, but by an indefinite margin which runs transversely from side to side.
The superior surface may be further divided into three areas, a superior, an anterior, and a right, following the general direction of these portions of the surface, but they are not clearly marked off from one another by borders.
Their arrangement is as follows:-
The superior area of the superior surface lies in contact with the roof of the abdomen; it is convex on each side, and depressed near the median plane. The two convexities, of which the right is the more prominent, fit into the two cupole of the diaphragm; whilst the central depression, depressio cardiaca, corresponds to the position of the heart. The superior area (with the exception of a small triangle at its posterior part, between the separating layers of the ligamentum falciforme) is completely covered by peritoneum, and on it the division of the liver into right and left lobes is indicated by the attachment of the ligamentum falciforme.
The anterior area of the superior surface is triangular in shape, and after death is usually flattened, owing to the falling in of the anterior abdominal wall. In part it lies in contact with the diaphragm, which separates it from the rib-cartilages on each side, but at the subcostal triangle it comes into direct relation with the anterior wall of the abdomen, for a distance usually of two or three inches below the xiphi-sternal articulation. It has a complete peritoneal covering, and gives attachment, as far down as the umbilical notch at the inferior border, to the ligamentum falciforme, which connects it to the anterior abdominal wall.
The anterior passes gradually into the upper and right areas, but it is distinctly separated from the visceral surface by the sharp margo anterior of the organ. The umbilical notch is often continued upwards for some distance on the surface as a slit-like fissure.
The right area of the superior surface is convex and extensive, and lies in contact with the diaphragm, which separates it from the inner surface of the lower ribs, and also, above, from the inferior margin of the lung and pleura. Though sharply marked off by the inferior margin from the visceral surface, it passes without distinct limits into the other areas of the parietal surface It is completely covered by peritoneum.
The superior surface is smooth and shows no fissures, but the line of attachment of the ligamentum falciforme is taken as dividing the liver on this surface into a right and a left lobe.
Upon the posterior surface and inferior surface there are several clefts or depressions upon the surface of the liver, termed fossæ or fissures, which further subdivide the surfaces into lobes These fossæ, it should be noted, do not indicate any deep division of the liver into separate parts, but are only indentations upon the surface.
Porta Hepatis.—(1) The gate of the liver (O.T. portal or transverse fissure) is the equivalent in the liver of the hilum of other glands. It is a slit-like depression. where the vessels enter the gland, and whence the ducts emerge.
It is placed on the inferior surface, runs transversely from right to left, and measures about 2 to 21 inches in length. It is bounded anteriorly and posteriorly by prominent margins, and through it the hepatic artery, vena porta, and hepatic plexus of nerves enter the liver, and the hepatic ducts and many of the lymph vessels leave. To the anterior and posterior margins of the fissure are attached layers of peritoneum which constitute part of the lesser omentum.
The various structures found in the porta hepatis are arranged in the following way. The vena portæ lies posteriorly, and divides, in the fissure, into right and left branches, which run to right and left. The neck of the gall-bladder, with the cystic duct coming from it, lies at the right extremity of the fissure, and there the cystic duct bends downwards between the layers of the hepato-duodenal ligament.
The right and left bile ducts lie at their respective ends of the porta hepatis. and converge towards each other at the right extremity and lie anterior to the corresponding branches of the hepatic artery, and to the right side of the main vessel at their junction in the hepato-duodenal ligament. The nerves mainly invest the arteries, and the lymph vessels lie in the connective tissue which invests all these structures.
Two or three lymph glands are occasionally found in the porta hepatis, especially at the right end, near the neck of the gall-bladder, and when enlarged, they may press upon the ducts, and interfere with the passage of the bile.
The intervals between the vessels and other structures are filled in by loose connective tissue, which is continued inwards with the vessels as the fibrous capsule of Glisson.
When the porta hepatis is opened up, it is found to extend on the left as far as to the fossa venæ umbilicalis.
(2) Fossa Venæ Umbilicalis (O.T. Umbilical Fissure).-The fossa for the umbilical vein is a deep crevice-like fissure, situated in the inferior surface, running from before backwards, parallel to the gall-bladder, but about 1 to 1 inches to its left side. It begins in front at the margo anterior, which it intersects, and runs backwards to the left extremity of the porta hepatis. Within this fissure lies a rounded cord-like structure, the ligamentum teres hepatis, the remains of the left umbilical vein of the foetus. The fissure is often crossed by a bridge of liver tissue, the pons hepatis, which may even extend for the whole length of the fissure, and conceal the round ligament from view.
(3) Fossa Ductus Venosi.-At the posterior termination of the fossa venæ umbilicalis the ligamentum teres is usually attached to the left branch of the portal vein. Beyond that point it is continued backwards as a fine fibrous band, the ligamentum venosum (Arantii), which runs onwards to join the vena cava inferior. This fibrous cord is the remains of the ductus venosus, and it lies in a groove on the posterior aspect of the liver, called the fossa for the ductus venosus.
The umbilical vein and the ductus venosus in the foetus serve to convey the blood back from the placenta to the inferior vena cava.
The umbilical fossa and the fossa for the ductus venosus together form a continuous fossa on the inferior and posterior surfaces which divides them into a right and left lobe. This fossa is known as the fossa sagittalis sinistra, in contrast to the porta hepatis, and to the fossa sagittalis dextra, lying to the right of two fosse which is made up of the following two fossæ :
(4) Fossa Vesica Felleæ. The fossa for the gall-bladder is a slight depression which begins (often as a notch) at or near the margo anterior of the liver, and runs backwards and to the left, as far as the porta hepatis (Fig. 938). Its surface is, as a rule, not covered by peritoneum, and in it lies the gall-bladder, which is united to it by areolar tissue.
(5) Fossa Vena Cava.-The fossa for the vena cava is a deep groove, on the posterior surface, on the right side of the caudate lobe, in which the superior part of the vena cava inferior is embedded, immediately before it pierces the diaphragm.
The depressions for the gall-bladder and the vena cava are rightly called fossæ. In hardened specimens it will be seen that the fossa for the umbilical vein, the porta hepatis, and the fossa for the ductus venosus are really fissures.
Taken together, the five fosse are arranged somewhat in the form of the letter A (Fig. 938); the two lower divisions of the diverging limbs being formed by the fossa venæ umbilicalis and the fossa vesica felleæ respectively, and the cross-piece by the porta hepatis-all of which are placed on the inferior surface. The two upper divisions of the limbs are represented by the fossa ductus venosi and that of the vena cava, which meet above and are both placed on the posterior surface. The latter of these two-namely, the fossa of the vena cava, represented by the right upper division of the A-does not join the cross-piece (the porta hepatis), but is separated from it below by a narrow ridge of liver substance the processus caudatus (Fig. 938).
To the right of the A is the lobus hepatis dexter, to its left the lobus hepatis sinister. The interior of the A is filled by the lobus quadratus anteriorly and the lobus caudatus [Spigeli] posteriorly, both of which are described as parts of the right lobe, while the processus caudatus cuts across the stem of the A behind the cross-piece, and connects the lobus caudatus (Spigeli) to the lobus hepatis dexter.
Lobi Hepatis (Lobes of the Liver).-As has been pointed out, the attachment of the ligamentum falciforme to the superior surface of the liver divides that aspect of the organ into right and left lobes. Similarly, upon the inferior surface, the fossa sagittalis sinistra is taken as dividing this aspect into right and left lobes. Lobus Hepatis Sinister. The left lobe is much smaller and flatter than the right, and forms only about one-fifth of the whole mass.
Lobus Hepatis Dexter.-Its inferior and posterior surfaces of the right lobe are intersected by the three additional fossæ described above, and by them it is subdivided into other parts, which also are called lobes. These are the lobus caudatus [Spigeli] with the processus caudatus, and the lobus quadratus.
(1) The Lobus Quadratus.—This is a quadrilateral area upon the inferior surface, extending from the margo anterior in front to the porta hepatis behind. On the right, it extends as far as the fossa for the gall-bladder, and on the left to the fossa for the umbilical vein. The surface is flattened or concave, and is mainly in contact with the pyloric part of the stomach and the duodenum.
(2) The Lobus Caudatus [Spigeli] (O.T. Spigelian Lobe). This is a prominent rather quadrilateral area on the posterior surface of the liver, between the fossa for the inferior vena cava on its right, and the fossa for the ductus venosus on its left side.
Its superior limit is formed by the terminal part of the ductus venosus, as it bends to the right to join the vena cava inferior, while, inferiorly, it is free and forms the posterior boundary of the porta hepatis.
This extremity is often cut into by a notch or fissure (in which the cœliac artery lies, particularly in the fœtus), which marks off a larger and more prominent left part, the processus papillaris, projecting downwards behind the porta hepatis, and a smaller right part, the processus caudatus, which connects it (Fig. 938) with the inferior surface of the right lobe.
The posterior surface of the caudate lobe is free; it is placed vertically, and looks backwards and slightly to the left. The lobe has also another surface, which is hidden when in the body and in the hardened liver by the folding of the left lobe across it. By this folding there is formed a deep fossa (fossa for the ductus venosus), at the bottom of which will be found the remains of the ductus venosus.
(3) The processus caudatus (O.T. caudate lobe) is merely a narrow bridge of liver tissue which connects the caudate lobe with the right lobe proper. It is limited anteriorly by the porta hepatis, and posteriorly by the fossa for the inferior vena cava. It forms the superior boundary for the epiploic foramen, and when the finger is placed in the foramen it rests against the caudate process, and has a vein on each side, i.e., in front and behind, separated by a layer of peritoneum.
Facies Posterior (Posterior Surface). This portion of the parietal surface is directed backwards, and lies in contact with the diaphragm, as the latter passes down on the posterior abdominal wall. It is very irregular in shape, and presents the following parts:-(1) The "uncovered area" of the right lobe; (2) the suprarenal impression; (3) the fossa for the vena cava; (4) the caudate lobe, separated by the fossa for the ductus venosus from (5) the oesophageal groove, which belongs
to the left lobe.
(1) The "uncovered area" of the right lobe (Fig. 938) is a considerable portion of the posterior surface of the right lobe-varying from 1 to 3 inches (37 to 7.5 cm.) in width, and from 3 to 5 inches (7.5 to 12.5 cm.) in transverse measurement-which is devoid of peritoneum. Over this uncovered portion, which looks more medially than backwards, the liver and diaphragm are in direct contact, and are united by areolar tissue; here too is established a communication by small veins between the portal circulation of the liver and the systemic circulation of the diaphragm.
(2) Impressio Suprarenalis.-On the "uncovered area," immediately to the right of the vena cava, is a triangular impression (Fig. 938), produced by a portion of the right suprarenal gland, which projects upwards from the superior extremity the right kidney, between the diaphragm and liver.
(3) Fossa Vena Cava.-At the left extremity of the "uncovered area" the inferior vena cava lies vertically, embedded in a fossa of the liver substance, between the caudate lobe on the left and the adjacent part of the uncovered area on the right, both of which project over the sides of the vein, almost hiding it from view (Fig. 938); sometimes they actually meet and form a pons hepatis across the back of the vein.
(4) Lobus Caudatus [Spigeli].This has already been described-see above. The superior recess of the omental bursa separates the posterior surface of the caudate lobe from the diaphragm, which latter, in turn, separates it from the thoracic part of the descending aorta just before that vessel enters the abdomen.
(5) The Impressio Esophagea, or esophageal groove, is situated on the posterior surface of the left lobe, to the left of the superior end of the caudate lobe, but