Question

Implantation of the zygote takes place at which of the following embryonic stages?
A) Gastrula
B) Morula
C) Blastula
D) Single-celled

Answer 1

Hint: Implantation is considered as the early stage of pregnancy. It happens when a fertilized egg attaches to a woman’s uterus. Implantation occurs during days six to twelve after conception. The embryo and the endometrium undergo changes before implantation.

Complete answer:
The first phase of implantation is known as ad plantation. There are sixty-four cells in the blastocyst stage. It is arranged as inner and outer cells. The outer cells make up the periphery of the zygote and are known as trophoblasts. The inner cells stick together to form the inner cell mass. It is also known as the ICM. ICM develops within the embryo. The outer layer develops into a part of the placenta and the mother feels cramped. This is the process of implantation.

After fertilization, the zygote is formed, which is single-celled. The zygote develops into a cell mass known as a morula. The stage at which it attaches to the uterus (implantation) is known as blastocyst or blastula. The stage which follows the blastula stage is known as gastrula.

Additional Information: The signs of the implantation process include the following: vaginal bleeding and spotting begin at the time of implantation, mild to moderate uterine cramps can occur due to the changes in the hormone, and headache and mood swings are also noticed during this period.

Thus, the correct answer is option ‘C’ i.e, Blastula.

Note: Human chorionic gonadotropin (hCG) aids in maintaining the pregnancy while the placenta assumes control. Hence, the concentration of hCG will be highest when the woman is pregnant. This is the principle of home pregnancy testing kits.