DEVELOPMENT OF ZYGOTE (IMPLANTATION)

After fertilization, the zygote is propelled down the oviduct by peristaltic contraction. The lining of the oviduct is ciliated but the cilia are so small that they probably play no part in propelling the zygote. Immediately the zygote reaches the uterus which takes up to a week in humans. It has already undergone mitotic division to form hollow sphere of cells called blastocyst.
After several days, the blastocyst becomes embedded in the lining of the uterus by the process called Implantation, where it continues its development. The trophoblast which is the outer layer of cells surrounding the blastocyste develops a small finger like outgrowths known as trophoblastic villi, this helps to protect the surrounding tissues of the uterine wall. While the villi helps to protect the surrounding tissues of the uterine wall. While the villi helps to absorb as nutrient.
As development proceeds, the product of implantation is an embryo called foetus, which is enveloped by a protective foetal membrane. The innermost membrane called the amniotic cavity and the fluid is called amniotic fluid. The amniotic cavity protects the foetus by the cushening effect of the amniotic fluid in which the effect is suspended. To accommodate the growing foetus during the period of pregnancy, the uterus expands coupled with the thickening of its wall and a great increase in vascular tissues. When the foetus reaches a  certain size of birth, parturition takes place. The period time from fertilization to birth is called gestation period. It takes 36 weeks in man
Child birth occurs in three main stages. In the first, the cervix is enlarged by the pressure created by the baby in its sac of amniotic fluid, which may burst at this time.., this is called dilation. The second occurs as the baby is forced out of the uterus and through the vagina the outside, this is time explosion while in the third and final, the placenta is expelled from the mother’s body within ten minutes after the birth of the baby, this is called placental delivery.
At birth the mammary gland which have been developing greatly during the pregnancy starts to secretes milk by the process called lactation which helps to provide the body with nourishment and a continuous source antibodies during the first few month of life. The milk is release immediately.

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