Question

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 cell.

Answer 1

Blastocyst, a characteristic stage of the fetus of a mammalian. It is a type of blastula which develops from the morula, a berry-like cluster of cells. In the morula, a space between the cells of the inner cell mass and the enveloping layer emerges.

Complete answer:
From the trophoblast and endometrium, the placenta develops about 5 weeks after implantation. Around 5-7 days after fertilisation, the blastocyst is inserted in the uterus. The implantation takes place through the blastocyst's trophoblast coat, which adheres to the uterine endometrium. Since implantation in the uterus, the embryo requires oxygen and nutrients from the mother through this adhesion.

Structural shifts in both the blastocyst and endometrial wall render implantation possible. The region pellucida, referred to as hatching, covers the blastocyst breaches. This removes the physical size limit of the embryonic mass and exposes the blastocyst's outer cells to the inside of the uterus. In addition, the mother's hormonal shifts, especially a peak in luteinizing hormone (LH), prepare the endometrium to receive the blastocyst and envelop it.

Hence, the correct answer is option (A)

Note: In vitro fertilization (IVF) use of blastocysts includes nurturing a fertilized egg for five days before sending it to the uterus. It could be a fertility therapy approach that is more viable than conventional IVF. Blastocysts' inner cell mass is the origin of embryonic stem cells, which are commonly used in stem cell treatments, including reconstruction, substitution and regeneration of cells.