April 17, 2022
Do you guys still remember how we control pregnancy in I/GCSE Biology?
Hormones
- Body processes controlled by chemicals (hormones)
- In I/GCSE Biology, Produced by organs called glands
- Pass from glands into bloodstream, transports them around the body
- Target organ – the organ the hormone affects
The menstrual cycle
- Day 5
- Follicle stimulating hormone (FSH) starts to be released by pituitary gland in brain
- Hormone travels in blood o ovaries
- Egg begins to develop
- Day 7
- Egg signals to ovaries as it develops
- Ovaries start to produce oestrogen
- Lining of the womb builds up
- Day 15
- Ovaries produce a lot of oestrogen – brain detects this
- Brain stops producing FSH and produces luteinising hormone (LH)
- LH triggers release of egg (ovulation)
- Day 28
- If egg not fertilised = lining of uterus is shed
- Causes menstruation bleeding (period) lasts a few days
- Cycle starts again
- FSH stimulates egg to mature, Oestrogen doesn’t cause egg to release, LH stimulates egg release
- In I/GCSE Biology, If pregnant then progesterone is made by ovaries.
- Oestrogen and progesterone continue being produced
- Progesterone helps maintain womb lining
The contraceptive pill
- Pill to stop women from becoming pregnant
- In I/GCSE Biology, Hormones in pill have same effect on pituitary gland as oestrogen
- Hormones stop pituitary gland making FSH = no egg will mature in ovaries
Benefits and problems
- Large amounts of oestrogen = blood clots (block arteries)
- In I/GCSE Biology, Two types of pill available – combined and mini pill
- Combined – low doses of oestrogen and progesterone – increased risk of women developing blood clots
- Mini pill – progesterone only – causes fewer side effects, must be taken punctually, less reliable than combined
Fertility drugs
- In I/GCSE Biology, FSH levels too low = ovaries don’t release eggs – women can’t become pregnant
- Treated by injecting FSH into blood
- FSH – fertility drug as it stimulates ovaries to produce mature eggs
- Treatment doesn’t always work, more than one egg can be released (twins, triplets, quadruplets)
That's all~