from The American Heritage® Dictionary of the English Language, 4th Edition
- n. The growth of a rapidly dividing group of cells around a more slowly dividing group of cells, as in the formation of a gastrula.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The expansion of one cell sheet over other cells, as takes place during gastrulation or secondary intention wound healing.
from the GNU version of the Collaborative International Dictionary of English
- n. Epibolic invagination. See under invagination.
from The Century Dictionary and Cyclopedia
- n. In embryology, that kind of gastrulation in which the inclusion of the hypoblastic blastomeres within the epiblastic blastomeres appears to result from the growth of the latter over the former, instead of being the consequence of a proper emboly, or true process of invagination of the hypoblast within the epiblast. See emboly. Also epibole, epibolism.
As epiboly proceeds, the ectoblast cap spreads out over the macromeres until it completely encloses them; at all times, ectodermal nuclei are distributed more or less evenly throughout this superficial cell sheet.
The onset of epiboly coincides with a period of mitotic quiescence throughout the ectoderm.
With the onset of epiboly, the ectoblast has become hemispherical, as reflected by the foreshortening of the 2a and 2c derivatives in this slightly dorsal view.
LR1, and that the progress of epiboly over the next three or four hours coincides with mitotic quiescence of the ectoblast.
The ectoderm originates as a roughly hemispherical cap of micromeres that sit atop the macromeres (top row); this cap spreads by epiboly over the four macromeres until its edges converge at the vegetal pole.
Warga RM, Kimmel CB (1990) Cell movements during epiboly and gastrulation in zebrafish.
You can see the early scrambling of cells in the blastula, migration during epiboly and blastopore closure, and convergence in the formation of the body axis fairly easily.
Ilyanassa) this convergence occurs by epiboly, as illustrated in Morphogenesis and the secondary axis of the spiralian embryo.