Question

Implantation

A. begins 24 hours after fertilizationis usually completed
B. 6 days after ovulation
C. begins as the inner cell mass adheres to the endometrial
D. wallinvolves embedding of the blastocyst into the uterine wall

Answer 1

Implantation occurs about a week after fertilization when the blastocyst embeds into the endometrium. The release of ß-HCG is critical for maintaining pregnancy and is measured in pregnancy tests. Implantation failure can lead to the blastocyst being shed during menses. Option D is correct.

Step-by-step explanation:

Implantation is a critical stage in early pregnancy that begins shortly after fertilization. Approximately a week after fertilization, the blastocyst reaches the uterus and starts the implantation process by embedding into the endometrial wall.

This interaction between the blastocyst and the endometrium is facilitated by the trophoblast cells, leading to the formation of the embryonic stage of development. Implantation is essential as it allows the embryo to receive nutrients and oxygen from the mother. A failure in implantation can result in the blastocyst being shed during menses.

It is also during implantation that the hormone human beta chorionic gonadotropin (ß-HCG) is released, which maintains the corpus luteum and ensures adequate levels of progesterone to support the developing embryo. Pregnancy tests measure the levels of ß-HCG to confirm pregnancy.