52 DIGESTION. 



What do we mean by "intestinal digestion"? . 



Soon after passing the pylorus, food comes in contact with the 

 alkaline secretions of the small intestine and of the liver and pan- 

 creas. In the small intestine the food is still further prepared for 

 absorption, and from this part of the alimentary tract the digested 

 food is taken up for body nutrition. 



Describe the process of digestion in the small intestine. 



By the peristaltic action of the gut the food is carried on through 

 the length of the organ, but its progress is more or less impeded 

 by the valvulse conniventes. These folds of the mucous coat not 

 only retard the too rapid advance of food, but cause it to be thor- 

 oughly exposed to the action of the digestive fluids. 



How is the peristaltic action regulated? 



By the sympathetic system of nerves. Auerbach's plexus lies 

 between the circular and longitudinal muscular coats. It is also 

 known as the plexus mesentericus. 



How is the blood-supply regulated? 



Also by the sympathetic system. Meissner's plexus lies beneath 

 the mucous coat, and is regarded as the source of control of the 

 blood-supply and of the function of absorption. 



What are the glands peculiar to the small intestine ? 

 Lieberkiihn's, Brunner's, and Peyer's glands. 



Describe Lieberkiihn's glands. 



These glands (or follicles or crypts) are thickly distributed over 

 the whole surface of the small and large intestine, being larger in 

 the large intestine. They are simply tubular depressions in the 

 mucous membrane, lined with columnar epithelium, which contains 

 occasional large " goblet "-cells. 



What are Brunner's glands ? 



They are found in the duodenum alone, and are situated in the 

 submucous tissue. They resemble the pyloric glands of the stom- 

 ach, and, like them, are usually compound glands. The duct of 

 the gland passes up through the mucous membrane and opens at 

 its surface. 



What are Peyer's glands? 



These are of two varieties: (1) solitary; (2) agminate. 



