The liver is the largest gland of the human body.It has the shape of a flattened ellipsoid, passes almost transversely across the upper portion of the abdominal cavity, and is composed of two lobes, a much larger right lobe and a smaller left one. It is soft in consistence and has a peculiar brownish-red color.
It has a markedly convex superior surface, which is also directed some-what anteriorly, and a similarly convex posterior surface. The greater portion of the inferior surface, on the contrary, is concave and of irregular shape. The superior and inferior surfaces unite in a sharp anterior border which is rounded off toward the right end of the liver, while the posterior and inferior surfaces pass into each other without demarcation.
The lower surface possesses a characteristic form on account of the softness of the hepatic tissue being influenced by the neighboring organs. It contains the porta hepatis (portal fissure), a transverse, rather deep and broad fissure which is situated almost in the middle, i. e., almost equidistant from the anterior and posterior margins (but some-what nearer the latter), and about midway between the left and right ends of the liver (but nearer the former). It gives entrance to the hepatic artery (ramus hepaticus proprius), the much larger portal vein, which has usually already divided into its two chief branches, the right and left branches, and the hepatic nerves accompanying the artery. It gives exit to the hepatic duct (usually in two main components), which unites with the cystic duct just below the porta hepatis to form the ductus choledochus (communis), and it also gives passage to a number of lymphatic vessels which run to the hepatic glands (five or six) situated in the immediate vicinity.
The vessels at the porta hepatis are so situated that the ductus choledochus is anteriorly and to the right, the hepatic artery anteriorly and to the left, and the portal vein posteriorly and between the two.
The vessels reach the porta hepatis by the hepatoduodenal ligament and in the porta itself are surrounded by a layer of connective tissue which accompanies them and their ramifications for a certain distance, and also forms a thin layer upon the surface of the liver known as the fibrous capsule of the liver (capsule of Glisson).
In addition to the transverse porta hepatis, the inferior surface of the liver also presents two approximately parallel longitudinal fissures which pass in a sagittal direction and form an H-shaped figure with the porta hepatis, although they are much shallower than the latter. They are known as the right and left sagittal fissures. The first is crossed at about its middle by the caudate process, so that it consists of two separated halves, an anterior, the fissure for the gall-bladder, and a posterior, the fissure for the vena cava. The left sagittal fissure is also differentiated into two portions, which are, however, directly continuous with each other at the left margin of the porta hepatis; the anterior is the umbilical fissure and the posterior the fissure for the ductus venosus.
The fissure for the gall-bladder contains the gall-bladder (vesica fellea) and is correspondingly broad and shallow; the fissure for the vena cava transmits the inferior vena cava, which is firmly adherent to the hepatic tissue and is not infrequently bridged over by a layer of connective tissue, the ligament of the vena cava. The vena cava during its passage through the liver receives the efferent hepatic vessels, consisting of a series of lesser and two greater hepatic veins, near the superior margin of the posterior surface of the liver.
The umbilical fissure contains the obliterated umbilical vein, which forms the round ligament (ligamentum teres) of the liver, and extends to the anterior hepatic margin, where it forms a notch, the umbilical notch. The fissure for the ductus venosus contains the obliterated ductus venosus (ductus Arantii), which is connected with the ligamentum teres by means of the left branch of the portal vein.
The left lobe of the liver is situated to the left of the left sagittal fissure. It includes only about one-fourth of the total mass of the liver, and is distinctly concave upon its inferior surface.
Since this concavity is produced by the stomach, which is normally situated below the left lobe of the liver, it is called the gastric impression, and an esophageal impression is also made upon the left lobe by the esophagus as it passes into the cardia. Below and to the right, the lower surface of the left lobe exhibits a convexity, the tuber omentale, which corresponds to the concave lesser curvature of the stomach. In the adult liver the tip of the left lobe gradually tapers out into a fibrous process, the fibrous appendix.
The right lobe of the liver includes all of the tissue to the right of the left sagittal fissure.
Upon the inferior surface, however, the right lobe in a restricted sense is to the right of the right sagittal fissure, the portions of hepatic tissue between the two fissures and separated by the porta hepatis being known as the quadrate lobe and the caudate (Spigelian) lobe.
The former is in front of the porta hepatis toward the anterior border of the liver and is a slightly elevated rectangular area; the latter lies behind the porta hepatis, and is smaller but more prominent than the quadrate lobe, being demarcated from the surrounding hepatic tissue by deep fissures. The right and caudate lobes are connected by a rather narrow caudate process, which divides the right sagittal fissure into halves, and the rounded left lower angle of the caudate lobe, which is opposite the caudate process, is called the papillary process. The caudate lobe is situated behind the pars flaccida of the lesser omentum in the vestibule of the bursa omentalis, which it completely fills.
The inferior surface of the right lobe, in the restricted sense, presents a number of markings produced by the neighboring viscera. The most pronounced is the renal impression resulting from the right kidney and situated beside the caudate lobe; in front of this is the less distinct duodenal impression; to the right and separated by a flattened ridge is the colic impression, produced by the hepatic flexure of the colon; and the right suprarenal body usually produces an inconstant concave depression immediately beside the fissure for the vena cava. These impressions, due to the marked plasticity of the liver parenchyma, are very transitory in character and are visible in the liver removed from the cadaver only when it has been previously hardened.
Upon the upper surface of the liver the boundary between the right and the left lobes is indicated by the falciform (suspensory) ligament, which, passing downward from the liver surface, envelops the round ligament like a mesentery. Upon this surface the right lobe seems to be a homogeneous structure and there are no formations corresponding to the caudate or quadrate lobes. At the anterior border of the liver the previously mentioned umbilical notch forms the division between the two main lobes.
The posterior surface of the liver, within the boundaries of the right lobe, exhibits a broad area uncovered by peritoneum, but upon the left lobe this uncovered area is limited to the narrow space between the attachment of the two layers of the coronary ligament. The remaining portion of the liver, except the porta hepatis, is completely invested by peritoneum.
The liver substance consists of lobules which are visible microscopically, but are indistinctly separated from each other; they are polygonal in form and about the size of a barley-corn. The center of the lobule is usually brownish- red, while the periphery is frequently of a yellowish tinge.
The liver substance is very soft and brittle.
The liver is situated in the right hypochondriac, epigastric, and left hypochondriac regions, and fills the right cupola of the diaphragm and a portion of the left one; in the middle it is in relation with the central tendon and its posterior surface is in contact with the crura of the diaphragm. It is also in relation with the viscera, which make impressions upon its lower surface, namely, the stomach, the superior and descending portions of the duodenum, the gall-bladder, the right kidney and suprarenal body, the hepatic flexure of the colon, and the inferior vena cava.
The periphery of the lobule is of a distinct yellow, particularly in the so-railed fatty liver. Since slight degrees of fatty infiltration are very frequent in the liver, the color is quite frequently noticeable in the cadaver.
The following points indicate the relation of the liver to the skeleton. The posterior surface is opposite the ninth and tenth thoracic vertebrae. During inspiration the highest point of the liver is upon the right side in the fourth intercostal space, and its lower border follows the costal arch as far as the median line, where it is usually about three finger-breadths below the tip of the xiphoid process of the sternum. The entire right half of the liver is considerably lower than the left, and while the left lobe is completely concealed behind the left costal cartilages, the right one extends below the inferior margins of the seventh to the tenth ribs, and in this situation is immediately behind the muscular portion of the anterior abdominal wall.
The average length (transverse diameter) of the liver is 30 to 36 cm., its height is 20 to 22 cm., and its greatest thickness is 7 or 8 cm.
The left lobe is very variable in length and not infrequently extends to the spleen. In this situation the liver parenchyma terminates quite gradually in the fibrous appendix, in which are found vasa aberrantia of the liver, blind bile-ducts and their ramifications, structures which also occur in other portions of the surface of the liver, particularly in the fibrous capsule beneath the peritoneal coat and in the ligament of the vena cava. The fibrous appendix probably results from a marked atrophy of the tip of the left lobe produced in the fetus by the pressure of the growing stomach. This would also explain the varying length of this lobe in different individuals.
The gall-bladder or vesica fellea serves as a reservoir for the bile secreted by the liver, and is situated in the fissure for the gall-bladder upon the inferior surface of the viscus. It is a pear-shaped sac, usually distended with bile, and consequently of a brownish-green or green color. It presents a rounded fundus, which in the distended condition projects beyond the anterior hepatic margin, and a constricted neck, which gradually passes into the cystic duct. Between the two is the body of the gall-bladder. The relations of the gall-bladder are dependent upon those of the liver. The fundus is placed below the right ninth or tenth costal cartilage and the neck and cystic duct arc directed toward the right. The upper non-peritoneal surface of the gall-bladder is connected with the liver substance by fibrous tissue; the lower surface is invested with peritoneum.
The wall of the gall-bladder is of moderate thickness and contains a weak muscular coat.
In the distended state the mucous membrane is elevated in narrow rugae, which undergo mani-fold decussations and give the inner surface of the gall-bladder a peculiar reticulated appearance
The cystic duct is the immediate continuation of the neck of the gall-bladder, and is a short irregularly cylindrical structure which turns sharply to the left near the porta hepatis and unites with the hepatic duct to form the ductus choledochus. Its caliber is smaller than that of the hepatic duct, and its mucous membrane is arranged in folds which pursue a slightly spiral course and constitute the spiral valve (valve of Heister). Corresponding to these folds the outer surface of the duct usually presents distinct constrictions.
The ductus (communis) choledochus arises immediately in front of (below) the porta hepatis by the junction of the hepatic and cystic ducts and runs in the hepatoduodenal ligament to the right side of and anterior to the portal vein; it passes behind the superior portion of the duodenum to the posterior and inner wall of the descending portion, where it forms the longitudinal fold and empties into the duodenum in common with the main duct of the pancreas.
The blood-vessels of the liver hold a peculiar relation to the viscus and one that is not encountered in any other portion of the human body. The organ possesses two afferent vessels, the larger of which is the portal vein. This arises behind the head of the pancreas by the union of the superior mesenteric and splenic veins, and transmits to the liver the venous blood from the intestines, the stomach, the pancreas, and the spleen. The other vessel is the hepatic artery, which comes off from the coeliac artery and ramifies chiefly in the wall of the gall-bladder (the cystic branch), about the bile-ducts, and in the fibrous capsule of Glisson, its capillaries forming venules which empty into the intrahepatic branches of the portal vein. The hepatic veins are the efferent vessels of the liver, and their contained blood has consequently passed through two sets of capillaries, t. e., first through those of the digestive tract and then through those of the liver. The lymphatics of the liver run to the hepatic lymphatic glands at the porta hepatis, from these to the coeliac lymphatic glands, and thence to the truncus intestinalis or directly into the cisterna chyli. The nerves of the liver enter the viscus with the hepatic artery as the hepatic plexus, and are furnished by the sympathetic and the pneumogastric.
The liver is developed as a protrusion of the embryonic intestinal wall at the site of the subsequent duodenum. This protrusion appears in about the third week of development and is double, the two halves subsequently fusing to form a single organ and a single duct (the hepatic or common duct). The gall-bladder arises as a lateral protrusion of the hepatic duct. In the fetus and even in the new-born the liver is enormous, being relatively much larger than in the adult.
The circulation in the liver has intimate relations to the circulation in the fetus. The round ligament of the liver is the remains of the obliterated umbilical vein, i.e. f of the single vein which passes through the umbilical cord from the placenta and transmits blood laden with nutritive material from the placenta to the fetus. The umbilical vein empties partly into the right branch of the small portal vein of the fetus and partly directly into the vena cava through the ductus venosus (ductus Arantii). When the placental circulation is interrupted by birth, both the umbilical vein and the ductus venosus become obliterated, and the digestive activity of the intestine causes the portal vein to dilate and assume its role as the chief afferent hepatic vessel. The umbilical vein is transformed into the round ligament and the ductus venosus into the ligament of the ductus venosus.
Human Anatomy (1909) by DR. Johannes Sobotta (1869-1945) Professor of Anatomy in the university of Wurzburg