A FUNCTIONAL DIFFERENTIATION OF THE GASTROINTESTINAL TRACT

Abstract

Needham (1942) in the glossary of his book "Biochemistry and Morphogenesis" defines "functional differentiation" as the differentiation of tissues as the result of forces arising out of the functions which they are performing. The functions of the adult gastrointestinal tract are mainly digestion and assimilation of food stuff. The cell population of the stomach and intestine, by a combination of forces, maintain these functions. To do so, various groups of cells have specialized both in their morphology and in their chemistry. The gradual development of the cell population of the embryo towards this adult pattern of morphology and chemistry may be regarded as maturation. Hence a chronological account of the evolution of such a pattern may be considered desirable. But to reach that end, which we call maturation, other "forces” must arise which are capable of performing functions necessary for the process of development. Those forces therefore must be regarded as essential aspect of important “functions” even if only transient functions. Failure of these transient functions may result in arrested development. Hence it is important to add to the chronological data the indices of adult function these transient forces which are chemical in nature and those which provide the energy for the process of maturation. A histological study of the developing gastrointestinal tract may provide the morphological indices of maturation. Histochemical studies can indicate these chemical forces that are necessary for the complete functional differentiation of the organ. The histological differentiation of the gastrointestinal tract of the domestic fowl has been described by several investigators and since the domestic fowl was readily available, most of the investigations in these present studies were made using chick embryos.