B1 - The Menstrual Cycle Flashcards
Describe the 4 stages of the menstrual cycle
On the day 1, the bleeding starts because the uterus lining breaks down for about 4 days
From day 4 to 14, the lining of the uterus builds up again into a thick spongy layer full of blood vessels ready to receive a fertilised egg
An egg is developed and then released from the ovary at day 14
The wall is maintained from day 14 to 28. If no fertilised egg has landed on the uterus wall by day 28, the lining starts to breakdown and the cycle repeats
What is the menstrual cycle?
The monthly release of an egg from the ovaries and the build-up and breakdown of the protective lining in the uterus
What are the 4 hormones involved in the menstrual cycle?
FSH (follicle stimulating hormone)
Oestrogen
LH (luteinising hormone)
Progesterone
Describe the roles of the menstrual hormones in the menstrual cycle
FSH is produced in pituitary gland and causes egg to mature in one of the ovaries and stimulates the ovaries to produce oestrogen
Oestrogen which is produced in the ovaries causes the pituitary gland to produce LH and stop producing FSH
LH is produced in the pituitary gland and stimulates the release of the egg in the middle of the menstrual cycle
Which hormones can reduce fertility?
Oestrogen
Progesterone
How does oestrogen reduce fertility?
If it is taken every day, it stops the production of FSH meaning that eggs can’t develop
It is taken as a pill
What does the pill consist of?
High levels of both oestrogen and progesterone
Why does the pill contain progesterone?
It also reduces fertility by producing a thick mucus that the sperm can’t get through
What was the problem with the pill in the past and how has this been solved?
The high levels of oestrogen had many strong side-effects so the amount of oestrogen in the pill was reduced
A progesterone-only pill was also made for people who still had side-effects
What are the 2 advantages of the pill?
It prevents pregnancy over 99% of the time
Reduces the risk of some types of cancer
What are the 3 disadvantages of the pill?
It isn’t 100% effective
Causes side-effects in some people
Doesn’t protect against STDs
What is the advantage and disadvantage of the progesterone-only pill?
Fewer side effects but not as effective
How do we increase fertility with hormones?
FSH and LH are injected to stimulate egg production and release
What is the advantage of this way of increasing fertility?
Helps a woman to become pregnant
What are the 2 disadvantages of this way of increasing fertility?
Doesn’t always work (people sometimes spend a lot of money to get it to work)
Too many eggs could be stimulated resulting in unexpected multiple pregnancies
Describe how IVF helped couples to have children
Collecting eggs from the woman and fertilising them in the lab with the man’s sperm
They are grown into embryos and transferred to the woman’s uterus
What are the 3 disadvantages of IVF?
Some women have a strong reaction to the hormones
Some reports of an increased risk of cancer
Multiple births can happen if more than one embryo grows into a baby
