ENTODERM

From Big Medical Encyclopedia

ENTODERM (entoderma; Greek ep-tos inside + derma skin; a synonym an endoderm) — the internal, or lower, germinal leaf which is formed in development of a germ at metazoans.

A bookmark and allocation of germinal leaves (see) at various animals is carried out in the different ways (see the Gastrulation). At coelenterates the gastrulation comes to an end with formation of two primary germinal leaves — primary ectoderm (epiblast) and primary entoderm (hypoblast). At chordates E. it is allocated from material of a blastoderm already in the first phase of a gastrulation, i.e. earlier, than the mesoderm and a chord, and represents from the very beginning not primary, but secondary entoderm. At a germ of amphibians an entoderm of l ny cells get by invagination under hordo-mesodermal material, forming a continuous entodermalny vystilka of primary gut. At birds, mammals and the person at this stage of development of a germ from an epiblast the average germinal leaf (mesoderm) stands apart, cells to-rogo originally accumulate in the tail of a periblast of a germ in the form of primary strip and primitive genzenovsky knot. Intestinal E. it is formed at them at the expense of the cells migrating from an outer surface of a germ inside through primary strip; at the same time from a germ cells of a hypoblast are forced out, to-rye form extraembryonic vitelline E., being a source of development of an epithelium of a vitellicle (see fig. 1 to St. Germinal leaves, t. 8, Art. 332). Among extraembryonic entodermalny cells of a vitellicle there are primary sex cells — gonocytes, to-rye at laying of gonads migrate in them by the amoeboid movement.

AA. is a source of formation of an epithelial vystilka of average department of an intestinal tube and its derivatives (a liver and a pancreas). At vertebrate animals and the person from E., according to

N. G. Hlopin (1946), accurately expressed entodermalny type of fabric including the following kinds of an epithelium is formed: epithelium of a stomach, intestines, liver, biliary tract, pancreas.

At the majority of animals as a result of the evolutionary shift of borders between an ectoderm and an entoderm the front gut and its derivatives are covered by a multilayer epithelium of ectodermal type (see Metorizis). A number of researchers carries an epithelium of a front gut (a multilayer flat epithelium of an oral cavity, gullet) and respiratory tracts (a multirow ciliary epithelium of a trachea and bronchial tubes) to derivatives of an entoderm. There is, however, an opinion that the specified types of an epithelium develop not from material E., and from a special rudiment — a prechordal plate.

See also Germ, the Organogenesis.

Bibliography: Volkova O. V. and Baking M. I. Embriogenez and age histology of internals of the person, M., 1976; e r l about in and E. Sh. N, the Histogenesis and a differentiation of digestive glands, M., 1978; D yu to and r E. Cellular interactions in development of animals, the lane with English, M., 1978; Carlson B. M. Fundamentals of embryology on Pettena, the lane with English, t. 1 — 2, M., 1983;

Knorre A. Г^ Embryonal histogenesis, JI., 1971 * A. A. Klishov,

Яндекс.Метрика