Menstruation
Biology: Cambridge International A Level, topic 15.1.13
The Menstrual Cycle
The menstrual cycle is a monthly cycle, which involves the maturation (process of maturing) and release of an egg. If sexual intercourse has occurred, this can result in pregnancy.
Key hormones
- The menstrual cycle is controlled by four hormones from the endocrine system:
- Follicle Stimulating Hormone (FSH)
- Oestrogen
- Luteinising Hormone (LH)
- Progesterone
Stages
- The menstrual cycle can be divided into four stages depending on the levels of the hormones.
Eggs
- A female is born with all of her eggs ready, but only one egg will mature each month once the female reaches puberty.
Menstrual Hormones
The menstrual cycle is controlled by four hormones from the endocrine system. These hormones are:
FSH
- FSH stands for Follicle Stimulating Hormone.
- It is released by the pituitary gland and causes an egg in the ovary to mature.
- FSH also stimulates (encourages) the production of oestrogen.
Oestrogen
- Oestrogen is produced in the ovaries and causes the development of the thick, spongy uterus lining.
- Oestrogen also stimulates the production of Luteinising Hormone (LH) and inhibits (stops) the production of FSH.
LH
- LH stands for Luteinising Hormone.
- LH is produced by the pituitary gland and stimulates the release of a mature egg on Day 14 of the menstrual cycle.
- This release is called ovulation.
Progesterone
- Progesterone is produced in the ovaries after ovulation.
- It is responsible for maintaining the lining of the uterus during days 14-28.
- When progesterone levels drop, this triggers the breakdown of the lining. This marks day 1 of the next menstrual cycle.
- Progesterone also inhibits (stops) the release of LH and FSH.
Test yourself on Menstruation
How frequent is the menstrual cycle?
What happens on day one of the next menstrual cycle?
In females, puberty triggers the menstrual cycle. Which of the following are true of the menstrual cycle?
How do menstrual hormones affect the production of one another?
Which hormone causes an egg in the ovary to mature?