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

Hint: Placenta is an organ developed in the pregnant human female. It develops in the female's uterus. The function of the placenta is to provide oxygen and nutrients to the developing baby and at the same time, it helps to remove waste from the baby's blood.

Complete answer:Humans have a chorioallantoic placenta meaning placenta developing from the chorion and allantois extraembryonic membranes. The dimensions of the placenta are approximately 22cm in length and 2-2.5 cm thick. It is thick in the central region and thin on its outer edges. The weight of the placenta is approximately 500gms.
The placenta is a temporary organ delivered immediately after the baby's birth. It connects the baby via the umbilical cord. It contains two umbilical arteries and an umbilical vein.
When the blastocyst implants in the endometrium of the mother, development of the placenta begin. The placenta is made up of both maternal and embryonic tissue. The outer layer of the placenta is made from the trophoblast. This outer layer is divided into two further layers: the underlying cytotrophoblast layer and the overlying syncytiotrophoblast layer. The placenta grows throughout pregnancy.
Functions of the placenta-
1. It helps in the attachment of the fetus to the uterine wall of the mother.
2. It provides water, nutrients, and oxygen to the developing fetus.
3. Removal of waste product from the fetus's body into the mother’s blood.
4. IgG antibodies pass through the placenta.

Note: The placenta formation is the feature of mammalian subclass Eutheria. The placenta is expelled out from the female's body during the third stage of labor.