What is "invagination"

Invagination \In*vag`i*na"tion\, n. [L. pref. in- + vagina sheath.]

1. (Biol.) The condition of an invaginated organ or part.

2. The inward movement of the wall of a tissue or cell, to form a cavity; also, the cavity thus formed.

3. Specifically: (Biol., Embryology) The inward movement of one part of the wall of a blastula, to form a gastrula; the process of gastrulation, in which layers of the ovum are differentiated.

   Note: In embolic invagination, one half of the blastosphere is pushed in towards the other half, producing an embryonic form known as a gastrula. -- In epibolic invagination, a phenomenon in the development of some invertebrate ova, the epiblast appears to grow over or around the hypoblast.

n. 1 (context medicine English) The process where an anatomical part invaginates upon itself or into another structure. 2 One of the methods by which the various germinal layers of the ovum are differentiated.

1. n. the condition of being folded inward or sheathed [syn: introversion]

2. the folding in of an outer layer so as to form a pocket in the surface; "the invagination of the blastula" [syn: introversion, intussusception, infolding]

Invagination is the infolding of one part within another part of a structure, a folding that creates a pocket. The term, originally used in embryology, has been adopted in other disciplines as well.