State the changes that take place in the uterus when:
(a) Implantation of embryo has occurred.
(b) Female gamete/egg is not fertilised.
(a) Changes in uterus when implantation occurred: Uterus prepares itself to nurture growing embryo. Its lining thickens. It is richly supplied with blood to no wish growing embryo.
(b) If ovum does not get fertilised: Then the thick and soft inner lining of uterus is no longer required; so it breaks. This inner lining of uterus along with blood vessels and dead ovum/egg comes out of vagina in the form of bleeding. It is called menstruation menstrual cycle in female.