ovulation Flashcards
what is the average cycle length?
28 days
how long is the follicular phase?
can vary
menstruation- ovulation (day 14)
how long is the luteal phase?
ALWAYS 14 days
what does rapid GnRH pulsatility lead to?
Rapid GnRH pulsatility leads to LH release
what does slower GnRH release lead to?
Slower GnRH release leads to FSH release
what triggers ovulation?
LH
what stimulates follicle development?
FSH
what releases GnRH and FSH/LH?
GnRH- hypothalamus
FSH/LH- anterior pituitary
when is the follicular phase?
menstruation- ovulation (usually day 0- 14)
however follicular phase can vary in time
what phase typically determines the length of a menstrual cycle?
Pre ovulatory phase (from the end of menstruation to ovulation) which is the follicular phase
what happens in the ovaries during the menstrual phase?
Menstrual phase (days 1-5)
-GnRH is released in slow pulses, triggering the release of FSH
-FSH triggers primary follicle to become a secondary follicle (this may take several cycles)
what is happening to the uterus in the menstrual phase?
-Fall in oestrogen and progesterone triggers release of prostaglandins causing uterine spiral arterioles to constrict
-Cells supplies by these arterioles die and the entire stratum functionalis of the endometrium sloughs off leaving the stratum basalis (2-5mm)
-50 to 150mls of blood, mucous ans epithelial cells sheds off from the endometrium, pass through the cervix and vagina
what are the 4 stages of follicular development?
- Primordial follicles
- Primary follicles
- Secondary follicles
- Antral/ Graafian follicles
explain the structure of a follicle?
Oocyte surrounded by granulosa cells
explain what is happening in the ovaries during pre ovulatory phase?
Follicles have 4 main stages: Primordial follicles, primary follicles, secondary follicles, antral/ graafian follicles
-Primordial follicles can mature into primary and secondary follicles at any stage during the menstrual cycle
-Once follicles reach secondary phase they develop FSH receptors
-Secondary follicles are stimulated by FSH, causing further development of secondary follcles
-As the secondary follicles grow, the granulosa cells surrounding them begin to release oestrogen
—>Oestrogen causes negative feedback to occur in the pituitary (lowering levels of LH and FSH)
—>Oestrogen also causes cervical mucous to become more permeable allowing sperm to penetrate the cervix around time of ovulation
-One follicle develops more than the others, this dominant follicle becomes the Graafian follicle/ Antral
what occurs to the uterus during the pre ovulatory phase?
-Oestrogen released from the secondary follicles and the Graafian follicle stimulate growth of the endometrium
-The stratum basalis undergoes mitosis to produce another stratum functionalis
-The endometrium doubles in thickness (5-10mm)
what day does ovulation occur?
day 14 in a 28 day menstrual cycle (14 days before menstruation)
what occurs in the ovaries during ovulation?
-Oestrogen peaks, stimulating more GnRH to be released from the hypothalamus
-GnRH causes anterior pituitary to release FSH and surge of LH
-(Approx 9 hours after released) The surge of LH causes the Graafian Follicle to rupture, releasing the secondary oocyte
-Secondary Oocyte is taken to the fallopian tube
what occurs in the uterus during ovulation?
-Progesterone and oestrogen continue to cause proliferation of the endometrium
what/ when is the post ovulatory phase?
The luteal phase
-this is the most constant phase
-lasts 14 days with little variation (starting from day after ovulation- menstruation)
