State in brief the changes that take place in a fertilized egg (zygote) till birth of the child in the human female reproductive system. What happens to the egg when it is not fertilized?
In humans the process of: Fertilisation is marked by the absence of the menstrual flow. Embryonic development of the zygote starts soon in fallopian tube and pregnancy begins. Embryo moves down to reach the uterus and gets attached to its thickened inner wall. The close attachment of the embryo with the uterus is called implantation. Embryo begins to divide. Uterus prepares itself to nurture growing embryo. Its lining thickens and is richly supplied with blood to nourish growing embryo. The embryo gets nutrition from the mother’s blood with the help of a special tissue called placenta. The placenta is a disc that is embedded in uterine wall. It contains villi on embryo’s side of tissue”. On mother’s side are blood spaces, which surround the villi. It provides a large surface area for glucose and oxygen to pass from mother to embryo. Developing embryo produces waste substances which can be removed by transferring them into the mother’s blood though the placenta. Development of child inside the mother’s body takes about 9 months.
When egg is not fertilized: Then the egg bursts along the uterus living, blood and mucous flows down as menstrual cycle begins. It is called menses also in human female.