1. Getting ready for pregnancy… …or not!
The menstrual cycle
Getting ready for pregnancy…
…or not!

2. What is the menstrual cycle?
Begins in females during puberty
Monthly (~28 days) sequence of events
It’s purpose is to coordinate the release of an ovum (egg) from one of the ovaries and prepare the lining of the uterus to receive the ovum, should it become fertilised.
In the absence of a fertilised ovum, the uterus lining breaks down and is shed – this is the source of the bleeding during a period
Each stage is carefully coordinated by hormones

3. The four stages of the menstrual cycle

4. Ovulation
Oestrogen and progesterone* are hormones produced by the ovaries at different stages of the menstrual cycle. Can you work out what their roles are?
* There are other hormones involved in this process produced by the pituitary gland in the brain, but you are only required to know about oestrogen & progesterone!

5. Ovulation
1. Oestrogen causes the lining of the uterus to thicken and grow. It also indirectly stimulates the release of an ovum on day 14 of the cycle by causing the pituitary gland (in the brain) to secrete Luteinising Hormone (LH)

6. Ovulation
2. Progesterone maintains the lining of the uterus. When the level of progesterone falls, the lining breaks down.

7. Ovulation
3. If a fertilised ovum implants into the uterus lining, the level of progesterone remains high, ensuring the uterus lining is maintained throughout the pregnancy.