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2.Human Reproduction
medium
In human female the blastocyst
A
forms placenta even before implantation
B
gets implanted into uterus 3 days after ovulation
C
gets nutrition from uterine endometrial secretion only after implantation
D
gets implanted in endometrium by the trophoblast cells.
(AIPMT-2010)
Solution
(d) : Implantation in endometrial uterine wall takes place at blastocyst stage of embryonic development. Before implantation, the blastomeres of early blastocyst get arranged into an outer layer called trophoblast and an inner group of cells attached to trophoblast called inner cell mass. It is the trophoblast layer through which blastocyst gets attached to the endometrium and the inner cell mass gets differentiated as the embryo.
Standard 12
Biology