The menstrual cycle Flashcards
What is the difference between male and female control of reproduction?
Male - continuous production
Female - Tract need to prepare for implantation, need to build in a waiting phase therefore, gamete production needs to be periodic.
What is the difference between the feedback on HPG axis in males and females?
Males - always negative feedback
Females - switch between negative and positive feedback depending on where in the cycle they are.
What two things need to be prepared?
Gamete (ovarian cycle)
Endometrium (uterine cycle)
When does ovulation occur?
Half way through ovarian cycle. This is when the gamete is released,
Describe the HPO axis
GnRH
FSH / LH
Inhibin and steroid hormones
Why is it important that GnRH is pulsatile?
Needed for fertility as if GnRH receptors are exposed to continuous GnRH they become descensitised.
What is endometriosis?
…
How is endometriosis treated?
GnRH agonists.
Start of menstrual cycle…
Start - no ovarian hormone production.
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What are the effects of FSH in follicular stage?
FSH binds to granulosa cells and causes them to multiply in a group - follicular development continues.
Theca interna appears so the follicle is now capable of oestrogen secretion.
Inhibin secretion begins.
What happens during the mid-follicular phase?
Need to nominate a dominant follicle (NAME) and prevent recruitment of any further follicles.
Two things happen:
- Follicular oestrogen: Positive feedback at hypothalamus and anterior pituitary
- Gonaddotrophin lovely can rise
- Effect seen on LH only
- Follicular inhibit rising (selective inhibition on FSH production by anterior pituitary)
What happens in preparation for ovulation?
Oestradiol and inhibit rise rapidly
Oestradiol production is no longer dependant on FSH
LH surge
Endocrine event that promotes ovulation
Ovulation
Release of oocyte form ovary
Effects of LH surge after ovulation?
Secrete oestrogen and progesterone in large quantities.
Inhibit continues to be produced
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What happens in Luteal phase?
Corpus luteum produces …
Uterine cycle…
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Layers of Uterus
Myometrium
Endometrium (epithelial lining) - made from functional layer and basal layer
Difference between two layers of endometrium?
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How does Uterus change over the menstrual cycle?
Early
Late
Early
Late
How do you get to end of cycle?
No more LH - corpus lute regresses
Dramatic fall in gonadal hormones (Oestrogen and Progesterone).
Relieving negative feedback and resets to start again.
How does end of cycle change if fertilisation occurs?
Syncitiotrophoblast
Pregnancy hormones?
Corpus Leteum, supported by placental hCG. produced steroid hormones to support the pregnancy.
What different phases are there in ovarian and Uterine cycle>
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What does oestrogen do during the follicular phase?
Fallopian tube function
Thickening of endometrium
Growth and motility of myometrium
What does progesterone do during the Luteal phase?
Further thickening of endometrium into secretory form.
What is a ‘normal’ cycle duration?
Normally 21-35 days
Variation in cycle duration due to variation in the length of the follicular phase. as Luteal phase its strictly 14+- 2 days
What factors affect the menstrual cycle?
Pregnancy
Lactation
Emotional stress
Low body weight
