Gut

Gut, a term technically used in zoology as equivalent to the enteron or alimentary canal. Three parts have to be carefully distinguished: (a) the fore-gut or stomodæum, lined by the outer layer or ectoderm, and formed from an anterior infolding or invagination; (b) the mid-gut or mesenteron, lined by the inner layer or endoderm, and formed from the original gastrula cavity; and (c) the hind-gut or proctodæum, lined by the outer layer or ectoderm, and formed from a posterior invagination. These three typical parts, thus distinguished according to their origin, vary greatly in size and function in different classes; but the mid-gut is the most important on account of its digestive function and because of its outgrowths (liver, &c.) in higher animals. It must also be noted that in vertebrate anatomy the pharynx, gullet, and stomach are sometimes called fore-gut; the small intestine, mid-gut; the large intestine, hind-gut; but embryologically these are all parts of the mesenteron defined above. See EMBRYOLOGY; and for the gut manufacture, CATGUT.