Question

Give an account of structure and development of blastocyst/blastula.​

Answer 1

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Blastocyst or blastula is a hollow ball like mulberry-shaped 32-64 cell stage of embryo. It has a cavity called blastocoel.

On 6-7 day of fertilization, blastocyst begins to attach with uterine wall. During the same time blastomeras arrange in two type of cells :-

• Trophoblast :- present on outer body surface which further forms placental part of attachment.

• Inner cell mass (=embryoblast) :- man of the cells which further differentiate to form embryo proper, I.e each part of embryo.

Trophoblast near the attachment with uterine wall further differentiate into syncytiotrophoblast and cytotrophoblast.