Structure of the Liver.The substance of the liver is composed of lobules, held together by an extremely fine areolar tissue, in which ramify the portal vein, hepatic ducts, hepatic artery, hepatic veins, lymphatics, and nerves; the whole being invested by a serous and a fibrous coat.
The serous coat (tunica serosa) is derived from the peritoneum, and invests the greater part of the surface of the organ. It is intimately adherent to the fibrous coat.
The fibrous coat (capsula fibrosa [Glissoni]; areolar coat) lies beneath the serous investment, and covers the entire surface of the organ. It is difficult of demonstration, excepting where the serous coat is deficient. At the porta it is continuous with the fibrous capsule of Glisson, and on the surface of the organ with the areolar tissue separating the lobules.
The lobules (lobuli hepatis) form the chief mass of the hepatic substance; they may be seen either on the surface of the organ, or by making a section through the gland, as small granular bodies, about the size of a millet-seed, measuring from 1 to 2.5 mm. in diameter. In the human subject their outlines are very irregular; but in some of the lower animals (for example, the pig) they are well-defined, and, when divided transversely, have polygonal outlines. The bases of the lobules are clustered around the smallest radicles (sublobular) of the hepatic veins, to which each is connected (Fig. 1089) by means of a small branch which issues from the center of the lobule (intralobular). The remaining part of the surface of each lobule is imperfectly isolated from the surrounding lobules by a thin stratum of areolar tissue, in which is contained a plexus of vessels, the interlobular plexus, and ducts. In some animals, as the pig, the lobules are completely isolated from one another by the interlobular areolar tissue (Fig. 1092).