CHAPTER IV 

 ABSORPTION 



General Principles. When food in the intestinal canal has 

 undergone its digestive changes it is absorbed. The alimentary 

 canal from esophagus to rectum consists of a single layer of 

 columnar epithelial cells placed on a basement membrane. 

 The soluble diffusible constituents of the food on one side and 

 the blood on the other side seem to offer favorable conditions 

 for filtration and osmosis. But it has been proved that the 

 activity of the epithelial cells is an important factor in absorption. 



1. Substances are absorbed from the intestine having the 

 same, less, or greater osmotic tension. 



2. Sugar and peptones, which are less diffusible than sodium 

 sulphate, are absorbed more rapidly. 



3. Non-dializable substances like egg albumin may be 

 absorbed. 



4. Some substances like peptone are changed in their passage 

 through the intestinal wall. 



There are two paths which absorbed products may take. 

 They may pass directly into the blood of the capillaries and 

 so into the portal system, in which case they are taken to the 

 liver, or they may pass into the lacteals of the lymphatic system, 

 forming chyle. In this case they pass through the thoracic 

 duct to enter the general circulation at the junction of the 

 left internal jugular and subclavian veins. It will, therefore, 

 be noted that the blood is the final objective point by each path. 



Absorption from the Stomach. The amount of absorption 

 in the mouth is quite insignificant and that from the stomach 

 is not very marked. Sugars, peptones, and proteoses may be 

 absorbed with difficulty. The same is true of water, which 

 is usually rapidly passed into the duodenum. Alcohol is 

 absorbed more rapidly and so are extractives of meat, which 

 form an important part of most thin soups and of beef tea. 



