Zusammenfassung der Ressource
The Menstrual Cycle
- The monthly release of an egg from a womens
ovaries and the build up and break down of the
protective lining in the uterus (womb) is called
the menstrual cycle
- Four stages
- Stage 1 - Lining of the uterus breaks down
- Stage 2 - Lining of the uterus builds up
- Stage 3 - Egg released
- Stage 4 - Lining of the uterus
maintained for about 14 days until
day 28. If no fertilised egg has landed
on the uterus wall by day 28 the
spongy lining start to break down and
the whole cycle starts again
- Hormones control different stages
- FSH (follicle-stimulating hormone)
- Causes an egg to mature in one of the ovaries
- Stimulates the ovaries to produce oestrogen
- Produced by the pituitary gland
- Oestrogen
- Causes pituitary to produce LH
- Inhibits the further release of FSH
- Produced in the ovaries
- LH (Luteinising hormone)
- Stimulates the release of an egg at
around the middle of the menstrual
cycle
- Produced by the pituitary gland
- Controlling Fertility
- Hormones can be used to reduce fertility
- Oestrogen can be used to prevent the
release of an egg so it can be used as
a method of contraception
- This may seem kind of strange (since naturally
oestrogen helps stimulate the release of eggs) But if
oestrogen is taken every day to keep the level of it
permanently high it inhibits the production of FSH
and after a while egg development and production
stop and stay stopped
- Progesterone also reduces
fertility e.g. by stimulating the
production of thick cervical mucus
which prevents any sperm getting
through and reaching an egg
- The pill is an oral contraceptive.
The first version was made in the
1950s and contained high levels
of oestrogen and progesterone
(combined oral contraceptive pill)
- There were concerns about a link between
oestrogen in the pill and side effects like
blood clots
- Pros
- The pills over 99% effective at preventing pregnancy
- Reduces the risk of getting some types of cancer
- Cons
- Isnt 100% effective
- It can cause side effects like
headaches, nausea,
irregular menstrual bleeding
and fluid retention
- It doesnt protect against STDs
- Increase it
- Some women have levels of FSH that are too
low to cause their eggs to mature. This means
that no eggs are released and the women
cant get pregnant
- The hormones FSH and LH
can be injected by these
women to stimulate egg
release in the ovaries
- Pro
- Helps a lot of people to get pregnant
- Cons
- It doesnt always work - some
women may have to do it many
times which can be expensive
- Too many eggs could
be stimulated resulting
in unexpected multiple
pregnancies
- IVF
- Involves collecting eggs from the
womans ovaries and fertilising them
in a lab using the mans sperm.
These are grown into embryos
- Once the embryos are tiny
balls of cells one or two of
them are transferred to the
womens uterus to improve
the chance of pregnancy
- FSH and LH are given before egg
collection to stimulate egg production (so
more than one egg can be collecting)
- Pro
- Fertility treatment can
give an infertile couple a
child
- Con
- Some people have a
strong reaction to the
hormone
- There have been some reports of
an increased risk of cancer due to
the hormonal treatment
- Multiple births can
happen if more than one
embryo grows into a baby