Page 129 - NCERT Science Class 10 English Medium

When a girl is born, the ovaries already contain thousands of
immature eggs. On reaching puberty, some of these start maturing. One
egg is produced every month by one of the ovaries. The egg is carried
from the ovary to the womb through a thin oviduct or fallopian tube.
The two oviducts unite into an elastic bag-like structure known as the
uterus. The uterus opens into the vagina through the cervix.
The sperms enter through the vaginal passage during sexual
intercourse. They travel upwards and reach the oviduct where they may
encounter the egg. The fertilised egg (zygote) starts dividing and form a
ball of cells or embryo. The embryo is implanted in the lining of the uterus
where they continue to grow and develop organs to become foetus. We
have seen in earlier sections that the mother’s body is designed to
undertake the development of the child. Hence the uterus prepares itself
every month to receive and nurture the growing embryo. The lining
thickens and is richly supplied with blood to nourish the growing embryo.
The embryo gets nutrition from the mother’s blood with the help of a
special tissue called placenta. This is a disc which is embedded in the
uterine wall. It contains villi on the embryo’s side of the tissue. On the
mother’s side are blood spaces, which surround the villi. This provides
a large surface area for glucose and oxygen to pass from the mother to
the embryo. The developing embryo will also generate waste substances
which can be removed by transferring them into the mother’s blood
through the placenta. The development of the child inside the mother’s
body takes approximately nine months. The child is born as a result of
rhythmic contractions of the muscles in the uterus.
7.3.3 (c) What happens when the Egg is not Fertilised?

If the egg is not fertilised, it lives for about one day. Since the ovary
releases one egg every month, the uterus also prepares itself every month
to receive a fertilised egg. Thus its lining becomes thick and spongy.
This would be required for nourishing the embryo if fertilisation had
taken place. Now, however, this lining is not needed any longer. So, the
lining slowly breaks and comes out through the vagina as blood and
mucous. This cycle takes place roughly every month and is known as
menstruation. It usually lasts for about two to eight days.

7.3.3 (d) Reproductive Health

As we have seen, the process of sexual maturation is gradual, and takes
place while general body growth is still going on. Therefore, some degree
of sexual maturation does not necessarily mean that the body or the
mind is ready for sexual acts or for having and bringing up children.
How do we decide if the body or the mind is ready for this major
responsibility? All of us are under many different kinds of pressures
about these issues. There can be pressure from our friends for
participating in many activities, whether we really want to or not. There
can be pressure from families to get married and start having children.
There can be pressure from government agencies to avoid having
children. In this situation, making choices can become very difficult.

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2024-25