LIVER. The liver is the largest glandular organ of the body. In man it is situated on the right side of the abdominal cavity immediately beneath the diaphragm. Its weight in the adult is approximately from three to four pounds, and its size is roughly indicated by the follow ing measurements: Greatest diameter about 12 inches, anteroposterior diameter about seven inches, thickness at different parts from one to three inches. The organ is divided into five lobes, of which the right and left are the prin cipal ones; the former comprising the greatest part of the bulk of the entire organ. On the under surface may be seen a square lobe lying anteriorly between the right and left lobes and known as the quadrate lobe. In a similar po sition between the right and left lobes at the posterior part of the organ is the Spigelian lobe, while a bridge-like lobe extending from the latter to the right lobe is known as the cau date lobe. The upper surface of the right and left lobes is convex and fits into the arch of the diaphragm. The lower surface of the or gan is more or less concave and is divided by five fissures. Of these a longitudinal furrow extends from the anterior to the posterior bor der of the organ separating the right from the left lobe; a transverse fissure extends at right angles from this at a point somewhat nearer the posterior than the anterior surface; it di vides the longitudinal fissure into an umbilical fissure in front (so called on account of its lodging the umbilical vein in the fcetus) and the fissure of the ductus venosus behind (on account of its lodging the ductus venosus in the fcetus). Between the lobus Spigelii and the right lobe of the liver is the fissure of the inferior vena cava, lodging that vein, while at the anterior edge of the organ at the side of the quadrate lobe is a fissure which accommo dates the gall-bladder. The transverse fissure is the most important, as it serves for the en trance into and emergence from the organ of the blood vessels, nerves and hepatic ducts.
The liver is held in place by five ligaments, four of which are simple folds of peritoneum, while the fifth, or ligamentum teres, is a round cord formed by the obliteration of the umbilical vein and extending from the anterior edge of the liver at the notch between the left and right lobes to the umbilicus and along the under sur face of the liver to its posterior border. The
peritoneal folds which serve the purpose of lig aments are a longitudinal one extending on the upper surface of the organ from the notch in front to the posterior border, a coronary liga ment which is found along the posterior bor der, and a right and a left lateral ligament. These peritoneal reflexions serve to hold the organ in place, keeping it more or less firmly in apposition with the diaphragm.
The blood vessels entering the liver are the hepatic artery and the portal vein; the former being a branch of the coeliac axis, the latter being the large venous trunk which is formed by the union of the superior mesenteric and splenic veins. Both the hepatic artery and por tal vein divide in the transverse fissure into two parts, a right and a left, which enter the substance of the right and left lobes, respec tively.
The hepatic veins are the efficient veins of the liver conveying the blood from this organ into the inferior vena cava. In addition to these vessels, the liver, like other organs, is supplied with large and numerous lymphatics. The nervous supply of the organ is derived from the left pneumogastric, the hepatic plexus of the sympathetics and from the right phrenic nerve. The bile ducts and hepatic ducts will be described below.
The gall-bladder is a small pear-shaped sac lying on the under surface of the liver. At its narrow end it opens into a small duct (cystic duct) which passes hack and down to loin the hepatic duct forming the common bile duct, which terminates in the duodenum. The gall bladder is the reserve sac in which bile is stored and by the contracting of which a uniform flow of this liquid is maintained.