The menstrual cycle
The menstrual cycle occurs from The physical changes a child’s body goes through when developing into an adult. until the end of reproductive life.
The purpose of the cycle is to prepare the female reproductive system for pregnancy.
It is controlled by the hormones A female sex hormone produced in the ovaries, which is responsible for puberty in girls and the regulation of the menstrual cycle. and Sex hormone produced by the ovaries and placenta..
A 28-day cycle:
Days 1-5
- Menstruation occurs – the Also known as a womb. This is where the fertilised egg (ovum) develops. lining breaks down and is released through the A muscular tube that leads from the cervix to the outside of a woman's body..
- Oestrogen levels are low.
- Progesterone levels are low.
Days 6-13
- The uterus lining begins to renew itself in preparation for the release of an egg.
- Oestrogen increases causing the initial repair of the uterus lining and its buildup.
Day 14
- The egg is released and this is called ovulation. It happens after oestrogen levels peak.
Days 15-28
- Progesterone levels peak after ovulation.
- Progesterone ensures the thickness of the uterus lining is maintained or the placenta and other pregnancy structures form if fertilisation has occurred.
- If pregnancy has not occurred the egg passes out of the vagina and the levels of both hormones drop, causing the cycle to begin again.
The male sex cell or gamete. present in the female reproductive system in the few days before ovulation, could fertilise an egg when it is released.
Any sperm that enter the female reproductive system in the few days after ovulation could also fertilise an egg.
Image caption, Days 1-5
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