(i) Functions of Placenta:
1. It supplies oxygen, water, nutrients and hormones from the mother to embryo.
2. It transfers. carbon dioxide and other waste materials from the embryo to the mother’s blood.
3. It shields the embryo from infections as it is impermeable to most of the micro organisms present in the mother’s blood.
4. It produces certain hormones like oestrogen and progesterone which are essential for the reproductive process.
The amnion or amniotic sac is made up of protective membranes that are formed around the embryo. It encloses a fluid-filled space which acts as a water-bath and an excellent shock absorb for the young embryo.
(ii) The embryo that develops in the placenta is maintained at a constant temperature, is well protected and nourished by the umbilical cord. Waste products of the foetus are also removed through it.
(iii) The interval of time between fertilization and birth is called the gestation period. It is about 280 days in human beings.