Attachment of blastocyst of uterine wall is called
a)	Fertilization	b)	Implantation	c)	Deplantation	d)	All of these

(b)

Implantation.

Implantation It is the attachment of the blastocyst to the uterine wall. It occurs after 7 days of fertilization. About 8 days after fertilization, the trophoblast develops into two layers in the region of contact between the blastocyst and endometrium.

These layers are (a) syncytiotrophoblast that contains non-distinct cell boundaries and (b) cytotrophoblast between the inner cell mass and syncytiotrophoblast that is composed of distinct cells. The portion of the blastocyst where the inner cell mass is located lies against the endometrium of the uterus. The blastocyst sinks into a pit formed in the endometrium and gets completely buried in the endometrium. The embedded blastocyst forms villi to get nourishment.

The cells of the inner cell mass differentiate into two layers (a) a layer of small, cuboidal cells known as the hypoblast layer, and (b) a layer of high columnar cells, the epiblast layer. Both the hypoblast and epiblast form a flat disc called the embryonic disc