Male and female
Male reproductive system
The male reproductive system contains these parts:
The two testes are contained in a bag of skin called the scrotum. They have two functions:
to produce millions of male sex cells called sperm
to make male sex hormones, which affect the way a man's body develops.
Sperm duct and glands
The sperm pass through the sperm ducts, and mix with fluids produced by the glands. The fluids provide the sperm cells with nutrients. The mixture of sperm and fluids is called semen.
Penis and urethra
The penis has two functions:
to pass urine out of the man's body
to pass semen into the vagina of a woman during sexual intercourse.
The urethra is the tube inside the penis that can carry urine or semen. A ring of muscle makes sure that there is no chance of urine and semen getting mixed up.
Female reproductive system
The female reproductive system contains these parts:
The two ovaries contain hundreds of undeveloped female sex cells called egg cells or ova. Women have these cells in their bodies from birth - whereas men produce new sperm continually.
Each ovary is connected to the uterus by an egg tube. This is sometimes called an oviduct or Fallopian tube. The egg tube is lined with cilia, which are tiny hairs on cells. Every month, an egg develops and becomes mature, and is released from an ovary. The cilia waft the egg along inside the egg tube and into the uterus.
Uterus and cervix
The uterus is also called the womb. It is a muscular bag with a soft lining. The uterus is where a baby develops until its birth.
The cervix is a ring of muscle at the lower end of the uterus. It keeps the baby in place while the woman is pregnant.
The vagina is a muscular tube that leads from the cervix to the outside of the woman's body. A man's penis goes into the woman's vagina during sexual intercourse. The opening to the vagina has folds of skin called labia that meet to form a vulva. The urethra also opens into the vulva, but it is separate from the vagina, and is used for passing urine from the body
The reproductive system of a child is not mature and needs to change as a boy or girl develops into an adult, so that the system is fully working. These changes begin between the ages of ten and fifteen. The time when the changes happen is called puberty.
The changes happen because of sex hormones produced by the testes in boys and by the ovaries in girls. Some changes happen in boys and girls, while others just happen in boys or girls.
Here are some changes that happen to both boys and girls:
underarm hair grows
pubic hair grows
body smell gets stronger.
growth rate increases
The time when the physical changes and emotional changes happen is called adolescence.
Here are some changes that happen only to boys:
voice breaks (gets deeper)
testes and penis get bigger
testes start to produce sperm cells
shoulders get wider
hair grows on face and chest.
Here are some changes that happen only to girls:
ovaries start to release egg cells (periods start)
hips get wider.
During sexual intercourse the man's penis releases semen into the woman's vagina. Sperm cells travel in semen from the penis and into the top of the vagina. They enter the uterus through the cervix and travel to the egg tubes. If a sperm cell meets with an egg cell there, fertilisation can happen. Fertilisation happens when an egg cell meets with a sperm cell and joins with it.
The fertilised egg divides to form a ball of cells called an embryo. This attaches to the lining of the uterus and begins to develop into a foetus (pronounced "fee-tuss") and finally a baby.
Development of the foetus
The foetus relies upon its mother as it develops. These are some of the things it needs:
nutrients (food and water).
It also needs its waste substances removing.
The foetus is protected by the uterus and the amniotic fluid, a liquid contained in a bag called the amnion.
The placenta is responsible for providing oxygen and nutrients, and removing waste substances. It grows into the wall of the uterus and is joined to the foetus by the umbilical cord.
The mother's blood does not mix with the foetus's blood, but the placenta lets substances pass between the two blood supplies:
oxygen and nutrients diffuse across the placenta from the mother to the foetus
waste substances, such as carbon dioxide, diffuse across the placenta from the foetus to the mother.
After nine months the baby is ready to be born. The cervix relaxes and muscles in the wall of the uterus contract, pushing the baby out of the mother's body.