GCSE Biology

1 - 4

bleeding starts

• uterus lining breaks down
• 4 days

4 - 14

lining of the uterus builds up again into a thick spongy layer full of blood vessels , ready to recieve a fertilised egg

an egg is released from the ovary at day 14

• wall
• 14 days until day 28

the spongy lining starts to break down and the whole cycle starts again

pituitary gland

• causes an egg to mature in one of the ovaries
• stimulates the ovaries to produce oestrogen

ovaries

• inhibits FSH
• causes the pituitary gland to produce LH

pituitary gland

release of an egg around the middle of the menstrual cycle

if it is taken every day it inhibits the production of FSH which will stop eggs maturing

• FSH
• LH
• stimulating the release of an egg in the ovaries

• the pituitary gland secrete FSH
• an egg starts to mature in the ovary
• FSH stimulates the ovary to secrete oestrogen
• the lining of the uterus thickens
• the lining of the uterus is ready for a fertilised egg
• oestrogen levels rise
• ovulation
• the pituitary stops secreting FSH
• the ovary stops secreting oestrogen
• inhibition of FSH secretion stops

• fertility drugs are used to make lots of eggs mature at the same time for collection
• the eggs are collected and placed in a solution in a petri dish
• a sample of sperm is increased
• the eggs and the sperm are mixed together
• the eggs are checked to make sure they have been fertilised and the early embryo are developing properly
• when the fertilised eggs have formed tiny balls of cells , 1 or 2 are placed in the uterus