458 THE HUMAN BODY 



being digested in the intestine. The common bile-duct, Dch, formed 

 by the union of the hepatic and cystic ducts, opens into the duode- 

 num. The blood which enters the liver by the portal vein and 

 hepatic artery passes out by the hepatic veins, Vh, which leave the 

 posterior border of the organ close to the vertebral column, and 

 there open into the inferior vena cava just before it passes up 

 through the diaphragm. 



The Structure of the Liver. On closely examining the surface 

 of the liver, it will be seen to be marked out into small angular 

 areas from one to two millimeters (-^ to ^ inch) in diameter. 



; ^ These are the outer sides of the superficial 



layer of a vast number of minute polygonal 

 masses, or lobules, of which the liver is 

 k m ^ U P5 similar areas are seen on the 

 surface of any section made through the 

 organ. Each lobule (Fig. 133) consists of 

 a number of hepatic cells supported by a 

 close network of capillaries; and is sepa- 

 n Fl 4 G \ 13 fu~ Di i a ^ am u* rated from neighboring lobules by con- 



illustrate the relationship 



of blood-capillaries, bile- nective tissue, larger blood-vessels, and 

 branches of the hepatic duct. The hepatic 



CelU are the P r P 6r tisSU6 elementS f the 



which a blood capillary liver, all the rest being subsidiary arrange- 



extends to L; D, a minute , . .', * 



bile-duct with which a bile- ments for their nutrition and protection, 

 capillary communicates. Each ig poiygo^ nucleated and very gran- 

 ular, and has a diameter of about 0.025 millimeter (T^TT f an 

 inch). In each lobule they are arranged in rows or strings, which 

 form a network, in the meshes of which the blood-capillaries and 

 bile-capillaries run. The blood carried in by the portal vein 

 (which has already circulated through the capillaries of the 

 stomach, spleen, intestines and pancreas) is conveyed to a 

 fine vascular interlobular plexus around the liver-lobules, from 

 which it flows on through the capillaries of the lobules them- 

 selves. These (Fig. 134) unite in the center of the lobule to form 

 a small intralobular vein, which carries the blood out and pours 

 it into one of the branches of origin of the hepatic vein, called 

 the sublobular vein. Each of the latter has many lobules emptying 

 blood into it, and if dissected out with them would look something 

 like a branch of a tree with apples attached to it by short stalks, 



