(i The uterine wall thickens that is richly supplied with blood.
(ii) A special tissue called placenta develops which connects embryo to the uterine wall that provides nutrients and oxygen to it.
(iii) Placenta is a disc which is embedded in the uterine wall. It contains villi on the embryo's side of the tissue. On the mother's side are blood spaces, which surround the villi. This provides a large surface area for glucose and oxygen to pass from the mother to the embryo.