Explain how does embryo form and how does child birth occur in female.

Explanation

The ovary releases ovum which enter in the oviduct (fallopian tube).
Fertilisation :
`rarr` The sperms enter through the vaginal passage during sexual intercourse.
`rarr` Sperms travel upwards and reach the oviduct where they may fertilise the egg.
Implantation and development :
`rarr` The fertilised egg (zygote) starts dividing and forms a ball of cells or embryo.
`rarr` The uterus prepares itself every month to receive and nurture the growing embryo.
`rarr` The embryo is implanted in the lining of uterus where it continues to grow and completes foetal growth. The lining of uterus thickens and is richly supplied with blood to nourish the growing embryo during pregnancy.
Placenta : The embryo gets nutrition from the mother.s blood with the help of a special tissue called placenta. It is a disc-like structure which is embedded in the uterine wall. It contains villi on the embryo.s side of the tissue. On the mother.s side there are blood spaces, which surround the villi. This provides a large surface area for passage of glucose and oxygen from the mother to the embryo. The developing embryo also generates waste substances which can be removed by transferring them into mother.s blood through the placenta.
Child birth :
The development of the foetus inside the mother.s body takes approximately nine months.
The child is born as a result of rhythmic contractions of the uterine muscles.