In: Biology
In embryology, cleavage is the division of cells in the embryo. The cells formed from cleavage is called as blastomeres and its with a formation of blastula. The cleavage can be holoblastic or meroblastic depending on the amount of yolk present in the egg. In the absence of a large concentration of yolk, four major cleavage types can be seen in isolecithal cells (cells with a even distribution of yolk) or in mesolecithal cells (moderate amount of yolk ) – bilateral holoblastic, radial holoblastic, rotational holoblastic, and spiral holoblastic, cleavage.
Coeloblastula is the development for eggs that undergo these radial cleavaging. In holoblastic eggs, the first cleavage always occurs along the vegetal-animal axis of the egg, the second cleavage is perpendicular to the first. From here, the spatial arrangement of blastomeres can follow various patterns, due to different planes of cleavage, in various organisms.