Regeneration Intestinal mucosa

Absorption of Lipides.—In order to be absorbed, simple and complex lipides must first undergo hydrolysis to aliphatic acids. These acids then combine with the bile salts to form water-soluble, diffusible complexes, which pass into the intestinal mucosa, where they interact with glycerophosphoric acid to regenerate the neutral fat, and thus enter the lymphatics. Hence, three factors are concerned in fat absorption (i.) the enzyme lipase and its activators (ii.) the bile salts, which act as carriers (iii.) the phosphorylation mechanism in the mucosa, which in turn, requires vitamin Bj (p. 257) and the hormone of the adrenal cortex (p. 415), as demonstrated by Verzar. This elaborate mechanism endows the organism with considerable power of discrimination in the absorption of lipides and lipoids, as shown by the preferential absorption of carotene. 

Although vitamin K is a fat soluble vitamin, only little stores are found in the body which have to be refilled permanently via dietary input. The role of vitamin K derived from bacteria in the colon is controversely discussed, as the concentration of biliary acids for the resorption the fatsoluble vitamin K is very low in the colon. In addition, only diseases of the small intestine lead to a deficit in vitamin K concentration which cannot be restored by K2 production of colonic bacteria. However, watersoluble vitamin Ks can be resorbed by the colonic mucosa. Maybe because of the little stores for vitamin K, the process of vitamin K-dependent carboxylation of proteins is part of a cycle with several steps during which vitamin K normally is regenerated (see Fig. 1) and thus can be used several times. 

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