DIGESTION 



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are no villi and no Brunner's glands, but the simple follicles (crypts of 

 Lieberkiihn) are both more numerous and larger than in the small 

 intestine. Much mucus is secreted by the wall of this part of the 

 intestine, but no enzymes have been isolated from its secretory 

 product. The ileo-cecal valve guards the opening between the small and 

 the large intestines. It consists of two folds of mucous membrane with 

 muscular fibers, projecting into the large intestine. The mucosa of the 



Diagram suggesting the functions of the liver. Parts of three hepatic cells are shown: P.V., 

 portal veins; H.A., hepatic arteries; B.C., bile capillary with its rootlets rising in the cytoplasm. 

 The arrows suggest some of the relations and movements of the various substances. 



rectum is thicker and more vascular than that of other parts of the gut. 

 It has three or four large permanent folds of a semilunar shape. The 

 lower portion of the rectum has two sphincters, made of tough bands of 

 circular muscle-fibers, the former being supported by the levatores ani 

 muscles. The nerve-supply of this part of the gut comes from two 

 sources, from the upper lumbar roots (sympathetic), and from the lower 

 mesenteric ganglion, the hypogastric plexus, the vagus, and the sacral 

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