Reproduction in human

You need to know the structure of the female reproductive organs (see the handouts you were given in class) and also the functions of the main parts.

Adolescence (puberty) is controlled by the sex hormones. The male sex hormone is called testosterone and it is produced in the testes. The female sex hormones are called oestrogen and progesterone and they are produced in the ovaries.

Male
Sperm is produced in the testes. A liquid is produced in the seminal vesicles and prostate gland and mixed with the sperm to form semen, which is stored in the seminal vesicles. The man?s penis is made of spongy tissue that fills up with blood when the man is sexually aroused. This makes the penis become erect. During intercourse the penis is inserted in to the woman?s vagina. Stimulation of the penis causes an ejaculation, where the semen is squirted from the seminal vesicles through the urethra (tube in the penis) into the woman?s vagina. The sperm then swim up into the vagina and then into the oviducts to fertilise an egg, if one is present.

Female
An egg is produced every month in one of the ovaries. It passes down the oviduct (or fallopian tube) and then into the uterus (womb). It then goes through the cervix (the part separating the uterus from the vagina) and then passes out through the vagina. However, if the woman has had sexual intercourse there are sperm in the oviducts. Fertilisation takes place when the sperm and the egg fuse to form a zygote.

The menstrual cycle
In the weeks leading up to ovulation (the release of an egg) an egg develops in one of the ovaries and the uterus develops a thick lining with lots of blood vessels. If an egg is fertilized it will fix itself to this lining and develop into an embryo. The blood supply will provide it with nutrients until the placenta grows. If an egg is not fertilized this thick lining is no longer needed and is passed out through the vagina. This is known as menstruation or the period.

The embryo develops in the uterus and grows into a fetus. It receives nutrients and oxygen from the mother via the placenta. It also gets rid of waste (such as CO2) this way. The mother?s and baby?s blood does not mix in the placenta, but they do pass very close to each other so that these substances can be transferred between them. The fetus develops inside a sac called the amnion that is filled with a liquid called the amniotic fluid. This provides protection for the baby. One of the first signs that a woman is about to give birth is when this sac breaks and the liquid inside passes out of the vagina. Muscular contractions in the uterus build up over the next hour or more until they become so strong that the baby is forced out of the uterus through the vagina. The umbilical cord that attaches the baby to the placenta is cut. The baby no longer receives oxygen from the mother so it needs to start breathing. The placenta is ejected from the uterus shortly after the baby (its often called the afterbirth).

There are more people born in the world each year than there are people who die. This means that the human population is rising rapidly. This is causing many problems, because in some countries there is not enough food or space for everyone. One solution is for people to use some form of birth control (such as contraceptives) to limit the number of children being born.

AIDS is a serious disease that is spreading rapidly throughout the world, especially in some areas such as Africa. AIDS is caused by the HIV virus. The virus is found in the body fluids (such as blood, semen, vaginal secretions etc). Anything that results in the fluids of an infected person entering a healthy person can result in transmission (the virus being passed from person to person). The most common ways of transmission are from sexual intercourse, the sharing of needles by doctors and drug addicts and through blood transfusions (though nowadays the blood is usually tested first). The use of condoms during sexual intercourse and the use of clean needles would help to limit the spread of AIDS.