332 



THE VERTEBRATE BODY 



intestine come into close contact with these capillaries and the molecules 

 of digested food pass by diffusion through the walls of the folds and the 

 walls of the capillaries. 



The liquefied foods are now in the blood and pass into the veins 

 where they are carried by the hepatic portal vein to the liver. We have 

 already mentioned bile secretion as one of the functions of the liver, but 



Liver- 



Gall bladder ■ 



Bile duct 



Duodenum — 



Pyloric sphincter ■ 

 Pancreas — 

 Jejunum — 



Ascending colon 



Ileocecal 

 sphincter- 



Cecum — 



Appendix- 



Esophagus 



— Stomach 



Transverse colon 



Ileum 

 Descending colon 



Sigmoid 

 ■ Rectum 



— Anal sphincter 



Fig. 23.2. The human digestive system. A part of the liver has been cut away to 

 show the part of the stomach lying beneath it. 



it has several other important functions as well. It acts as a storage 

 organ for certain important products such as carbohydrates, fats, and 

 vitamins. As blood rich in these substances enters the liver and passes 

 into the capillary network which surrounds the cells, the liver will 

 absorb and store any excess. Sugar is stored in the form of glycogen 

 which is released gradually between meals and thus maintains the proper 

 balance of this sugar in the blood. The liver also removes poisons from 

 the blood — we would be more easily injured or even killed by small 



