Question

The zygote passes through several developmental stages till implantation, Describe each stage briefly with suitable diagrams.

Answer 1

Developmental stages of embryo till implantation:

The zygote passes through several developmental stages till implantation, as follows :

• Zygote undergoes cleavage to form blastomeres.
• At the 8 celled stage the blastomeres are tightly packed and called the morula.
• Further divisions in the embryo result in the formation of a sphere with a cavity called the blastocoel. At this stage the embryo is called blastocyst.
• The blastocyst consists of an outer envelope of cells called the trophoblast and inner cell mass.
• The cells of trophoblast help to provide nutrition to the embryo.
• At the 64 cell stage the blastocyst attaches to the uterus.