The Menstrual Cycle
1) The cycle takes 28 days with ovulation about 14 days into the cycle.
2)The cycle is controlled by three hormones.
>FSH is made by the pituitary gland and causes the egg to mature and oestrogen to be produced.
>Oestrogen is produced by the ovaries and inhabits the further production of FSH. It stimulates the production of LH and also stimulates the womb lining to develop and receive the fertilised egg.
>LH is made by the pituitary gland and stimulates the mature egg to be released.
The artificial control of fertility
1)The contraceptive pill contains oestrogen that prevents pregnancy.
2)FSH can be given to a women to help her to produce eggs.
>The contraceptive pill contains oestrogen. This prevents the production of FSH so no eggs mature.
>If a woman can not produce mature eggs then FSH can be given. This is known as 'fertility treatment'.
1) It is very important that the internal conditions of the body are kept within certain limits.
2) Water and ion content, as well as temperature and blood sugar level, are all carefully controlled.
Water is leaving our body all the time as we breathe out and sweat. We lose any excess water in the urine (produced by the kidneys). We also lose ions in our sweat and in the urine.
We must keep our temperature constant otherwise the enzymes in our body will not work properly (or not work at all).
Sugar in the blood is the energy source for cells. The level of sugar in our blood must be controlled.