SEX CELLS

Male and female sex cells are necessary for reproduction.

Egg cells are the female sex cells. They are large and round. From puberty on, one egg matures and passes through a Fallopian tube approximately every twenty-eight days.

In the egg cell is not fertilised, it leaves the body through the vagina. Minor bleeding occurs, called menstruation or a period.

Sperm are the male sex cells. They are very small. From the beginning of puberty on, about 200 million of these aare produced every day.

FERTILISATION

FERTILISATION occurs when an egg cell and a sperm unite in one of the Fallopian tubes or in the uterus.

This first cell of the new human being has all the DNA of the two parents and is called a zygote. It divides numerous times and forms an embryo. Then the embryo is implanted in the wall of the uterus.

EMBRYO DEVELOPMENT

When the embryo is implanted in the wall of the uterus, it is ready to develop into a baby. The embryo needs food and oxygen to grow. It also needs protection.

First, it is protected by a sac called amnion, which fills with liquid.

Then, the placenta forms. It gives the embryo nutrients and oxygen from the mother.

The embryo is connected to the placenta by the umbilical cord.


After about eight weeks, when the main structures and organs have formed, the embryo is called a foetus.

PREGNANCY

PREGNANCY  is the period from the moment of fertilisation until the birth of the baby. This normally lasts about nine months. The mother´s body experiences many changes during this period.

CHOOSE THE CORRECT ALTERNATIVE IN EACH OF THESE SENTENCES

1. One egg cell matures and passes through the Fallopian tubes every two weeks/ twenty-eight days.
2. If the egg is / is not fertilised, it leaves the body through the vagina.
3. Two hundred million sperm are produced every day / month from the beginning of puberty.
4. A zygote / embryo is the fisrt cell of the new human being.
5. The zygote / embryo is implanted in the wall of the uterus.

STAGES OF LABOUR

The process of giving birth is called labour.


The involuntary muscles produce contractions in the uterus. The sac containing the foetus breaks. The liquid around the foetus is expelled.

There are three stages of labour:

-Dilation: the opening of the vagina dilates so that the baby can come out.

-Birth: the baby leaves the mother´s body.

-Afterbirth: the placenta is expelled.

If labour is difficult or dangerous for the mother or the baby, doctors perform a caesarean section to take the baby from the mother´s uterus.

NEWBORN BABIES

When a baby is born, the umbilical cord is cut. The mark left is called a belly button.


Newborn babies are about fifty centimetres long and weigh about three kilograms.

Babies born before term are called premature. Premature babies are kept in incubators, where they can develop and grow stronger.

LACTATION

Lactation is the period when babies get their nourishment from their mother´ s milk. If a mother cannot produce milk, infant formula is used. It is made from modified cow´s milk or soya milk. Breast milk is best, but formula provides many necessary nutrients.