(i) Placenta is the connecting link between the mother and the foetus. All the nutrients of the foetus are received through mother's blood via placenta. Also, the waste materials from foetus are taken via the placenta to mother's blood where it is finally disposed off. It also helps in the transport of glucose and oxygen to the growing embryo.
(ii) After fertilisation, a hormone called progesterone causes the thickening of uterine lining because of a large amount of blood vessels. The lining prepares itself to receive the fertilised egg and implant it into the spongy lining supplied richly with blood vessels and is required to provide nourishment to the fertilised egg (embryo).