Phase 1 = follicular phase (oestrogen is high, progesterone is basal)
Phase 2 = luteal phase (progesterone is high)
1 of 19
How long is the average menstrual cycle?
28 days
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How long is the follicular phase?
day 0 - 14
3 of 19
How long is the luteal phase?
day 14 - 28
4 of 19
What event occurs on day 14 (end of follicular phase)
Ovulation (egg is released)
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What is the meaning of oogenesis?
development of the female gamete
6 of 19
Describe + explain the process of oogenesis
- primordial germ cells migrate towards to gonadal ridge during early gestation
- gonad develops medial to embryonic kidney
- diploid oogonia divide by mitosis during foetal development
- birth- all oogonia arrested in 1st meiotic division- completed at p
7 of 19
Describe what events occur at puberty
- several primordial follicles are stimulated
- maturing oocytes within maturing follicles will undergo series of developmental changes that bring 1 secondary oocytes into a tertiary follicle at the point of ovulation
- ovulated secondary oocyte would hav
8 of 19
Describe the events that occur at ovulation
tertiary follicle (aka mature graafian follicle) ruptures to expel the secondary oocyte into the pelvic cavity
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What is the corpus luteum?
- a temporary structure needed to establish + maintain the pregnancy in females
- mature graafian follicle becomes corpus luteum
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What happens to the CL if the oocyte is not fertilised at ovulation?
corpus luteum undergoes luteolysis- stops secreting progesterone + degenerates into corpus albicans (fibrous mass of scar tissue)
11 of 19
What controls the menstrual cycle?
the brain- hypothalamus
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Outline how the hypothalamus controls the menstrual cycle
- Inputs to the hypothalamus causes release of GnRH which stimulates the anterior pituitary to release FSH + LH causing the ovary to produce oestrogen, progesterone + inhibin
Luteinising Hormone:
- produces precursors for oestrogen production
- stimulates maturation, ovulation of follicle
- maintains function of CL
15 of 19
Describe the negative feedback mechanism that controls the menstrual cycle
- inhibin secreted by granulosa cells in ovaries inhibit production of FSH
- Oestrogen produced by ovaries inhibits the secretion of LH + GnRH
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Why does the negative feedback mechanism only work 'most' of the time?
- the sensitivity of the brain to oestrogen changes in the late follicular phase
- increased oestrogen causes a positive feedback mechanism that stimulates the surge centre in the brain the produce more GnRH
- drive ovulation
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Describe the processes that occur to cause ovulation
- high levels of oestrogen from mature graafian follicles stimulates release of more GnRH + LH
- GnRH promotes release of FSH + more LH
- LH surge drives ovulation
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What does LH do in the luteal phase of the menstrual cycle?
- drives production of progesterone by CL
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Other cards in this set
Card 2
Front
How long is the average menstrual cycle?
Back
28 days
Card 3
Front
How long is the follicular phase?
Back
Card 4
Front
How long is the luteal phase?
Back
Card 5
Front
What event occurs on day 14 (end of follicular phase)
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