What is placenta? Describe its structure. State its functions in case of a pregnant human female. 

Placenta is a special tissue that forms a connection between the foetus and the mother. It is a disc embedded in the uterine wall, it contains villi on the embryo’s side of the tissue while there are blood spaces on the Mother's side, which surround the villi.

Function of placenta
The placenta acts as a respiratory and excretory surface. 
i. It provides a large surface area for glucose and oxygen to pass from the mother to
the embryo.
ii. It also helps to remove the waste substances generated by the foetus by transferring them into the mother’s blood.