What do you know What methods are there of controlling fertility naturally What methods are there of treating infertility What methods are there of contraception How do all these work Contraception and the treatment of infertility are based on the biology of fertility ID: 740681
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c The biology of controlling fertility
What do you know?What methods are there of controlling fertility naturally?What methods are there of treating infertility?What methods are there of contraception?How do all these work?Contraception and the treatment of infertility are based on the biology of fertility.There are some risks and ethics associated with fertility treatments.
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Fertility
Men are continuously fertileNegative feedback involving the effect of testosterone on FSH and ICSH (pituitary gland)Sperm are always being producedWomen have cyclical fertilityFertile for about 1-2 days following ovulationCaused by ovarian and pituitary gland hormone interaction2Slide3
Natural fertile period for women
Temperature rise of about 0.5oC after ovulationCaused by progesterone productionFertile for 1-2 days before egg disintegratesMucus of cervix also thinner at this time
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Infertility
This can be caused by: male sterility low sperm count defective sperm blockage of oviducts failure to ovulate (no FSH or LH)
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Artificial Insemination
Semen is collected and frozenUnfrozen and released together as a large sample at fertile period in uterusA donor can be used for this process if male is sterile
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Stimulating ovulation
Drugs to mimic action of FSH and LHDrugs to prevent oestrogens negative feedback on FSH secretion during luteal phaseMore eggs are maturedThis can lead to multiple pregnancy/births(These drugs are used in IVF also)6Slide7
In-vitro fertilisation (IVF)
Overcomes blocked oviductsEggs are fertilised outside the bodyProcessDrugs to produce more eggs givenEggs harvestedEggs mixed with semen in petri dish with nutrients (or sperm can be injected directly into the egg)Fertilised eggs incubated for 2-3 days (division 8 or more cells)2 or 3 embryos inserted into uterus through the vagina
Unused embryos frozen for later use
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Testing of genetics before implantation
In IVF cells can be taken for genetic screening and diagnosisPre-implantation genetic screening (PGS)Non specific checking of embryo fro single gene disorders and common chromosomal abnormalitiesPre-implantation genetic diagnosis (PGD)Specific checks for known chromosomal or gene defects
Ethics of this type of testing?
Reassurance/benefit OR designer babies/eugenics
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Improving chances of fertilisation in IVF
Eggs mixed with semen
OR
Sperm injected directly into the egg called
Intra cytoplasmic sperm injection (ICSI)
This can overcome problem
d
efective sperm or
low sperm count
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Contraception
Methods both natural and artificial to prevent conception or pregnancyBarriersCondomsDiaphragmCervical capFemidomIntrauterine devices (IUDs)
T shaped structure (plastic/metal) fitted into uterus prevents implantation by irritation
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Chemicals
Oral contraceptive pillSynthetic progesterone and oestrogen1 per day for 3 weeksMimic negative feedback of FSH and LH so no ovulationMorning after pillHigh levels of progesterone and oestrogen prevent implantation of fertilised eggMini pillProgesterone only pill
Thickens the cervical mucus, reducing sperm viability and uterus access
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Sterilisation
Vasectomy (men) sperm ducts cut and tiedTubal ligation (women)
cutting and tying of oviducts
Both effective but normally irreversible.
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c The biology of controlling fertility
What do you know now?What methods are there of controlling fertility naturally?What methods are there of treating infertility?What methods are there of contraception?How do all these work?Consolidate by reading chapter and completing questions, making own notes, completing scholar, multiple choice questions.
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