MP Board · Class 12 · Biology · Human ReproductionWhat is implantation? Describe the process and its significance in human reproduction.

Implantation is the process by which the blastocyst attaches to and embeds itself into the endometrium (inner lining) of the uterus, establishing a physical and physiological connection between the mother and the developing embryo.

1. Process: Following fertilization in the ampulla of the fallopian tube, the zygote undergoes cleavage to form a morula and subsequently a blastocyst. The blastocyst consists of an outer layer of cells called trophoblast and an inner cell mass. As it reaches the uterine cavity, the trophoblast cells interact with the endometrial lining, causing the uterine cells to proliferate and engulf the blastocyst. This securely embeds the blastocyst into the vascularized endometrium.
2. Significance: Implantation marks the formal establishment of pregnancy in mammals. Once successfully implanted, the trophoblast layer forms projections called chorionic villi, which interdigitate with uterine tissue to form the placenta. The placenta facilitates the exchange of respiratory gases, nutrients, and wastes, and secretes essential pregnancy maintenance hormones.