Class 12th Biology 2015 Set2 Delhi Board Paper Solution
Name the stage of human embryo at which it gets implanted. Explain the process of implantation.
The stage of the human embryo in which it gets implanted in the uterus is blastocyst.
The process of implantation can be explained as follows:
1. Fertilisation results in the formation of a diploid zygote.
2. As zygote moves through the uterus, mitotic divisions occur in the zygote that form 2, 4, 8, 16 daughter cells called blastomeres.
3. Embryo with 8 to 16 blastomeres is known as morula.
4. Morula undergoes further cleavage and develops into blastocyst; blastomeres of blastocyst get arranged into an outer layer called trophoblast and inner cells called inner cell mass.
5. Trophoblast layer of blastocyst gets attached to the endometrium while inner cell mass differentiate to form embryo.
6. After attachment, the uterine cells divide rapidly and causes the blastocyst to become embedded in the endometrium of the uterus. This leads to pregnancy.
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