Physiology Flashcards
What is the main axis involved in menstruation
Hypothalamic, ant. Pituitary gonadal axis
Describe the first stages of the HPG axis
- Activin causes hypothalamus to release GNRH
- GnRH travels to ant. Pituitary
- Ant. Pituitary releases LH and FSH
- LH and FSH travel to ovaries and casue oestrogen and inhibin release
What does inhibin do?
Inhibit activin, stopping release of GnRH, therefore reduces LH,FSH, OESTROGEN PROGESTERONE AND INHIBIN
What does FSH do
Stimulate follicle production until a dominant one is found
What does oestrogen do?
Regulate the cycle
What does LH do>
Cause transformation of dominant follicle to corpus luteum which produces progesterone
What does GnRh do?
Stimulate ant. Pituitary
What hormone causes progesterone to be released
GnRH - LH - change of dominant follicle to corpus luteum - progesterone
What does FSH do in the follicular phase?
- Causes stimulation of growing follicles
- Grows until main follicle is produced
- That then produces lots of oestrogen
- Oestrogen inhibits growth of other follicles
What is the name of the dominant follicle in follicular phase?
Graafian follicle
What does oestrogen do in the follicular phase?
- Stop other follicles growing
- Causes endometrial thickening
- Thins cervical mucus
- Inhibition of LH
What’s the relationship between oestrogen and LH at day 12 follicular phase?
Oestrogen rises past a point which causes LH stimulation ad causes LH spike at day 12
Describe the role of LH in changing Graafian follicle to ovum
LH spike causes Graafian follicle to become thinner, causing second oocyte release as it ruptures, secondary oocyte changes into optic and then matures into mature ovum that then is released and taken into fallopian tube by fimbriae
What hormones act on the old Graafian follicle
LH and FSH to change Graafian follicle to corpus luteum
What is the corpus luteum
Gland that starts to produce progesterone
Is degenerated when FSH and LH levels fall
Progesterone levels reduce then also
What does increased progesterone do? (3)
- Endometrium becomes ready to implant
- Negative feedback causes decrease in LH AND FSH
- Increases womens basal body temp
What is the menstrual phase>
End of the luteal phase the corpus luteum degenerates
Loss of corpus luteum = less progesterone
Less progesterone - contraction of spiral arteries
Contraction of spiral arteries = loss of blood supply and necrotic tissue that sheds.
What happens in the proliferative phase
Increasing levels of oestrogen due to increased LH AND FSH = repair of functional layer of endometrium
What happens in secretory phase
Ovulations occured, progesterone from corpus luteum results in the secretion of substances from endometrial glands and make uterus more welcoming for embryo
What is part of the uterine cycle
Proliferative, secretory and menstrual
What is part of the menstrual cycle
Follicular and luteal
What causes oestrogen to rise?
Follicular development and big release from first mature follicle
What happens if that ovum is fertilised by sperm at the start of luteal phase/end of follicular phase
Ovum + sperm = happy egg
Happy egg release b-HCG
B-hCG allows corpus luteum to keep developing and releasing progesterone
Secretory phase is contact
Until 8 weeks where placenta then takes over corpus luteum job
