154 



THE VITAL PROCESSES 



and the hepatic artery. The. portal vein collects the blood 

 from the stomach, intestines, and spleen, and passes it to 

 the liver. This blood is loaded with food materials, but 

 contains little or no oxygen. The hepatic artery, which 

 branches from the aorta, carries to the liver blood rich in 

 oxygen. In the liver the portal vein and the hepatic 



artery divide and sub- 

 divide, and finally empty 

 their blood into a single 

 system of capillaries sur- 

 rounding the liver cells. 

 These capillaries in turn 

 empty into a single sys- 

 tem of veins which, unit- 

 ing to form the hepatic 

 veins (two or three in 

 number), pass the blood 

 into the inferior vena 

 cava (Fig. 72). 



The liver secretes 

 daily from one to two 

 pounds of a liquid called 

 FIG. 72. Relations of the liver. Dia- ^le. A reservoir for 



gram showing the connection of the liver the bile is provided by 

 with the large blood vessels and the food a smSL \\ f membranous 



sack, called the gall 



bladder, located on the underside of the liver. The bile 

 passes from the gall bladder, and from the right and left 

 lobes of the liver, by three separate ducts. These unite to 

 form a common tube which, uniting with the duct from the 

 pancreas, empties into the duodenum. Though usually 

 described as a digestive gland, the liver has other func- 

 tions of equal or greater importance (Chapter XIII). 



