Invagination
From Free net encyclopedia
Invagination means to fold inward or to sheath.
Invagination, in biology, can refer to a number of processes.
One is one of the morphogenetic processes by which an embryo takes form, and is the initial step of gastrulation, the massive reorganization of the embryo from a simple spherical ball of cells, the blastula, into a multi-layered organism, with a differentiated germ layers: endoderm, mesoderm, and ectoderm. More localized invaginations also occur later in embryonic development.
Another is the formation of a cleavage furrow during cytokinesis in animal cells. Some bacteria also have an invagination of the cell membrane, called a mesosome. It is a tightly-folded region of the cell membrane containing all the membrane-bound proteins required for respiration and photosynthesis. Can also be associated with the nucleoid.