CBSE Class 10 Answered

Placenta:

Placenta is a special umbilical cord that develops in the fourth week of pregnancy. It establishes an intimate connection between the foetal membrane and the uterine wall.

Function of placenta:

The exchange of materials between the mother’s blood and the blood of foetus takes place through the placenta. It serves as a nutritive, respiratory and excretory organ of the foetus.

Blastocyst:

The blastocyst is a structure formed in the early embryogenesis of mammals, after the formation of morula. It possesses an inner cell mass (ICM), or embryoblast, which subsequently forms the embryo and an outer layer of cells or trophoblast, which later forms the placenta. The trophoblast surrounds the inner cell mass and a fluid-filled blastocyst cavity known as blastocoels or blastocystic cavity. The human blastocyst comprises 70-100 cells.