Question

With a well labelled diagram, describe cleavage up to blastula formation.

Answer 1

Hint: A process of the rapid division of cells that governs to the formation of the multicellular zygote is referred to as cleavage. The 6-32 cell hollow structure that is formed after a zygote undergoes cleavage is known as blastomere. Any cell that forms after the division of a fertilized egg is known as blastomere.

Complete answer:
The formation of the multicellular individual from a single-celled zygote, which withstands many rounds of cleavage or rapid cell division without rising in mass to form morula then undergo further cleavage to form the blastula. Later the cleavage generates over 100 cells. Every cell inside the blastula is recognized as the blastomere.
The blastula is usually a round layer of cells (the blastoderm) enclosing a fluid-filled or yolk-filled compartment known as blastocoel. In mammals, the blastula establishes the blastocyst in the next phase of development. The blastula finally establishes itself into 2 layers that are known as the Inner cell mass (which will become the embryo and known as embryoblast) and the outer membrane of trophoblast (that will become the placenta. Its function is to nourish the embryo). The structure formed is known as a blastocyst.

Note: Features of the cleavage stage are as follows:
-It is distinguished as an interval of the unprecedented immediate division of the cell. There is no development between divisions and the ratio of nuclear to cytoplasmic is reduced around 1000 fold. -There are different processes of cells lacking or possessing very short, G1 and G2 phases. Unequal cytokinesis occurs.