Question

What do you mean by implantation?
a) Fusion of male gamete with female gamete
b) Embedding of embryo in thick lining of uterus
c) Developing a special tissue between uterus wall and embryo
d) The period of gestation
e) None of these

Answer 1

Hint: Implantation is known as the stage of pregnancy during which the embryo adheres to the wall of the uterus which helps it receive oxygen and nutrients from the mother.

Complete answer:
In humans the implantation is known to occur about nine days after ovulation . before the implantation takes place the uterus undergoes certain changes so that it is capable of receiving the embryo. The uterus increases its thickness, gets supplied with numerous blood vessels and also grows its gland to boost secretions. Several lytic factors both in the uterine wall as well as secreted by the blastocyst plays an important role in the triggering of implantation. At first a loose connection is made between the blastocyst and the endometrium known as the apposition. Following apposition adhesion takes place that leads to a much stronger attachment of the blastocyst to the endometrium. Finally invasion takes place which is the most permanent form of attachment of the blastocyst to the endometrium.

So the correct option is B) Embedding of embryos in the thick lining of the uterus.

Note:
During the process of implantation the blastocyst secretes various autocrine factors that helps in the attachment to the endometrium. Among them the most widely known is the human chorionic hormone that apart from helping in implantation also helps to prevent menstruation in pregnant women.