human reproduction

• what happens during puberty?

  • during puberty, reproductive hormones cause secondary sexual characteristics to develop (facial hair, breasts, eggs maturing)
  • men = testosterone stimulate sperm production
  • women = oestrogen, physical changes, menstruation 9cycle lasts 28 days)
• the menstrual cycle

  • day 1 = menstruation starts, uterus lining breaks down for four days.
  • days 4-14 = lining builds back up
  • day 14 = ovulation
  • day 28 = wall is maintained, if egg has not landed in the uterus wall then the cycle repeats
• what is FSH?

  • produced in pituitary gland
  • causes egg to mature in the ovary in a follicle
  • stimulates ovaries to produce oestrogen
• what is oestrogen?

  • produced in ovaries
  • causes lining of uterus to grow
  • stimulates release of LH
• what is LH?

  • produced by pituitary
  • stimulates ovulation at day 14
• what is progesterone?

  • produced in ovaries by the remains of the follicle after ovulation
  • maintains uterine lining during second half of cycle. when progesterone level falls, the lining breaks down
  • inhibits release of LH and FSH
• oral contraceptives

  • contain hormones to inhibit FSH so no eggs can mature
  • very reliable
  • may cause side effects
  • no protection from STIs
• spermicides

  • kill or disable sperm
  • readily available
  • not very effective
• barriers

  • prevent sperm from reaching egg
  • protect against STIs , no side effects
  • may break and allow sperm out
• injection/implant/patch

  • slow release of progesterone to inhibit maturation and release of eggs for a number of months/years
  • very effective
  • injection lasts 12 weeks, patch lasts 7 days
• IUD

  • prevents implantation of an embryo or release of hormones
  • very effective, lasts 3-5 years
  • may cause period problems or infections
• abstinence

  • no side effects
  • unreliable, can risk unwanted pregnancy
• surgical

  • male + female sterilisation
  • permanent
  • involves surgery, risk of infection
• pros of IVF

  allows infertile women to have children
• cons of IVF

  • expensive
  • not 100% successful
  • could cause health risks
  • extremely emotionally and physically stressful
  • increases chances of multiple pregnancies
  • ethical risks of stored embryos