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tubular depressions in the epithelium of the intestinal mucosa of vertebrates and man, first described by the German scientist J. N. Lieberkühn in 1745.
The shape, size, and number of Lieberkühn’s glands, or crypts, differ in different parts of the intestine. The floor of each crypt reaches the muscular layer of the mucous membrane; the mouth opens into the intervillous lumina. The epithelium of the crypt consists of prismatic cells with a brushlike edge, mucous goblet cells, chromaffin cells, and Paneth’s cells. It is conjectured that the chromaffin cells manufacture serotonin, which upon entering the blood regulates the muscle tone of the vessels, and that the Paneth’s cells elaborate the enzyme enterokinase, which makes possible the conversion of trypsinogen to active trypsin. The deep epithelial cells divide intensively, serving to replenish the rapidly exhausted cells of the villi and the crypts themselves.