Female reproduction 2

• Graafian follicle - hormone control 


  • oestrogen levels in the graafian follicle are high
  • Oestrogen stimulates-
  • FSH and LH production by pituitary gland,
  • Expression of LH receptors on theca cells
  • FSH stimulates granulosa cell proliferation - more cells to produce oestrogen
  • LH and LH receptors stimulate androgen production by theca cells
  • High levels of androgen are converted to oestrogen by increased number of granulosa cells
  • Results in higher oestrogen levels and thus further FSH and LH stimulation
  • RARE positive feedback loop
• Ovulation - what happens to ovarian follicle


  • Extremely high oestrogen levels induce LH surge
  • LH surge indues secretion of proteolytic enzymes (lysosomal enzymes + collagenase)
  • which weaken follicle wall - allows oocyte to be released
  • LH surge increases blood flow to ovary which increases follicular wall pressure
  • Increased fluid accumulation in follicle antrum
  • Follicle wall ruptures - point of rupture called stigma
  • Oocyte released from follicle
• Corpus luteum function 


  • after ovulation the ovary enters the luteal phase of its cycle (everything up to ovulation is follicular phase)
  • Rapid invasion of blood vessels to form corpus hemorrhagicum
  • Pituitary LH causes luteinisation of remaining granulosa + theca cells in corpus hemorrhagicum.
  • New luteal cells ( newly formed corpus luteum) produce progesteone - pregnancy hormone.
• what is the stigma 


  • the area of rupture on follicle wall
  • where oocyte is released from follicle
• ovulation 


  • fimbriae (motile) of oviduct search for mature follicle ready to rupture on ovary.
  • fluid filled follicle on ovary + fimbriae ready to collect oocyte
  • ovulation occurs- follicle ruptures and releases oocyte.
  • Oocyte sucked into the oviduct
  • follicle rupture = release of the oocyte
  • the empty follicle contains some granulosa + theca cells - forms the corpus luteum.
  • Oocyte that leaves is surrounded by cumulus cells
• horse ovary - how different 


  • most species ovulate from the surface of the ovary
  • horses ovary turned inside out so ovulate internally. fimbriae form a tube inside ovary called - ovulation fossa.
• oocyte structure

  • zona pellucida
  • Polar body
  • Cumulus cells - modified granulosa cells external to zona pellucida.- move oocyte down oviduct towards the sperm.
  • Perivitelline space
  • Oocyte cytoplasm

  
• Luteal regression - sheep

  • corpus luteum remains for either - duration of luteal phase of ovarian cycle or early pregnancy.
  • If no pregnancy occurs the corpus luteum must regress at the end of the cycle.
  • Prostaglandin F2a secreted by uterus 10-15 days after Corpus luteum formation
  • Prostaglandin F2a is a luteolytic hormone
  • CL breaks down + ovary starts new follicular phase - luteolysis phase
• corpus luteum regression in sheep

  • corpus luteum produces oxytocin which travels down ovarian artery into uterus and binds to uterine oxytocin receptors
  • this causes uterus to produce PGF 2a causing
  • Lysis of corpus luteum
  • Stops progesterone production.