Menstrual cycle

The overall function of the menstrual cycle is to release an ovum into the reproductive system and for it to be successfully fertilised, implant and grow to term.

There are three main stages of the menstrual cycle:

1. Preparation: When the egg matures in the ovaries and the uterus wall lining has an increasing blood supply.
2. Ovulation: The release of an ovum from the ovaries to fallopian tubes.
3. Maintenance: When the blood supply of the uterus wall lining is maintained so that the egg may be fertilised and implant into the wall.

FSH [follicle stimulating hormone] is released from the pituitary gland when there are no significantly high levels of hormones in the bloodstream. It causes an egg to mature within a follicle in the ovaries.
Oestrogen is released from the ovaries as the egg begins to mature. It increases the blood supply to the uterus thus thickening the wall lining. It causes FSH to cease and LH to be released from the brain. LH causes the egg to be released from the follicle and causes the follicle to change structure into a corpus luteum. The corpus luteum is yellow. The corpus luteum produces progesterone. This maintains the blood supply to the uterus until the corpus luteum decays.

Oestrogen: develops secondary sexual characteristics in females.
Testosterone: ' in males.

1. Breast development
2. Increased body hair + pubic hair
3. Regulation of body mass - redistributed to hips and breasts
4. Development of sexual organs
5. Voice deepens

1. Development of sexual organs
2. Voice deepens
3. Pubic hair
4. Increased muscle mass