GCSE Biology

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GCSE Biology
2012-06-03 09:45:22
menstrual cycle controlling fertility

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  1. stage one is from day
    1 - 4
  2. stage 1 - day 1 is when the
    bleeding starts
  3. stage 1 - the ...... ...... .... ..... for about :
    • uterus lining breaks down
    • 4 days
  4. stage 2 is from day
    4 - 14
  5. in stage 2 the
    lining of the uterus builds up again into a thick spongy layer full of blood vessels , ready to recieve a fertilised egg
  6. stage 3 - .............................................
    an egg is released from the ovary at day 14
  7. stage 4 - the ..... is then maintanied for about
    • wall
    • 14 days until day 28
  8. if no fertilised egg has landed on the uterus wall by day 28 then
    the spongy lining starts to break down and the whole cycle starts again
  9. FSH is produced by the
    pituitary gland
  10. FSH
    • causes an egg to mature in one of the ovaries
    • stimulates the ovaries to produce oestrogen
  11. oestrogen is produced by the
  12. oestrogen
    • inhibits FSH
    • causes the pituitary gland to produce LH
  13. LH is produced by the
    pituitary gland
  14. LH stimulates the
    release of an egg around the middle of the menstrual cycle
  15. oestrogen can be used to prevent preganacy because it is a contraceptive and
    if it is taken every day it inhibits the production of FSH which will stop eggs maturing
  16. women can be injected with ............. and .... to increase fertility by :
    • FSH
    • LH
    • stimulating the release of an egg in the ovaries
  17. how do hormones control the mestrual cycle
    • 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
  18. what are the stages of IVF
    • 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