Question

Explain the phases in embryonic development from the morula stage till the establishment of pregnancy in a human female.

Answer 1

• The embryo with 8 to 16 blastomeres is called a morula.
• The morula continues to divide and transforms into a blastocyst as it moves further into the uterus.
• The blastomeres in the blastocyst are arranged into an outer layer called trophoblast and An inner group of cells attached to the trophoblast is called the inner cell mass.
• The trophoblast layer then gets attached to the endometrium, and the inner cell mass gets differentiated as the embryo.
• After attachment, the uterine cells divide rapidly and cover the blastocyst.
• As a result, the blastocyst becomes embedded in the endometrium of the uterus. This is called implantation and it leads to pregnancy.

Fertilisation and passage of growing embryo in the fallopian tube.