Question

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

Answer 1

The zygote passes through the following stages till implantations

1. The embryo with 8-16 blastomeres is called a morula.
2. The morula continues to divide and transforms into blastocyst as it moves further into the uterus.
3. The blastomeres in the blastocyst are arranged into a surface layer called trophblast and a cluster of interior cells attached to the trophoblast are called the inner cell mass.
4. The trophoblast layer then gets attached to the endometrium and inner mass cells get differentiated as embryo.
5. After attachment, the uterine cells divide rapidly to cover the blastocyst.
6. The blastocyst. becomes embedded in the uterin endometrium. This is called implantation.

Transport of ovum, fertilisation and passage of growing embryo through Fallopian tube