THE LIVER 163 



THE LIVER 



This great gland is covered with a fibrous membrane the cap- 

 sule of Qlisson. The capsule is covered with a single layer of ir- 

 regularly shaped, flat endothelial cells. 



Prolongations from the fibrous, visceral portion of Glisson's 

 capsule penetrate the organ from every side, and divide the entire 

 structure into compartments the lobules. 



The hepatic lobules are irregularly polygonal in transverse sec- 

 tion, and somewhat ovoid vertically. They are about two milli- 

 meters in diameter. 



Let us first examine the general plan of the vascular arrange- 

 ment, and later, the minute structure of the lobular parenchyma. 



The hepatic blood -supply comes from two sources: 1. The 

 venous drainage collected in the portal vein. 2. The arterial sup- 

 ply, provided from the aorta by the hepatic artery. The portal 

 venous blood is filtered through the liver instead of passing directly 

 to the ordinary destination of venous blood (the vena cava), in 

 order to contribute certain factors to the processes of digestion and 

 metabolism, while the smaller arterial supply is distinctly nutritive. 

 The hepatic duct is the common excretory conduit of the bile after 

 its formation by the parenchyma of the liver. 



The scheme of the organ will be understood by reference to 

 Fig. 107, which is purety diagrammatic. 



The portal vein enters the liver at the transverse fissure. It 

 divides and subdivides; and, reaching every part of the various 

 lobes, the terminal twigs are seen in the connective tissue of the 

 walls of the lobules. 



Branches from these termini of the portal or interlobular veins 

 penetrate the lobular areas, and immediately break up into capil- 

 laries, which form an intricate plexus throughout the lobule. The 

 blood from these capillaries is finally collected into a central or 

 intralobular vein, by means of which it is immediately drained from 

 the lobule. 



The central veins from a varying number of the lobules unite 

 outside of the latter, forming the beginning of the hepatic or so- 

 called sublobular veins; and sublobular veins from various lobular 

 areas unite, forming several (six or seven) large hepatic veins, which, 

 passing in the connective tissue framework, finally drain the blood 



