ovulation

Question 1

what is the average cycle length?

Answer 1

28 days

Question 2

how long is the follicular phase?

Answer 2

can vary

menstruation- ovulation (day 14)

Question 3

how long is the luteal phase?

Answer 3

ALWAYS 14 days

Question 4

what does rapid GnRH pulsatility lead to?

Answer 4

Rapid GnRH pulsatility leads to LH release

Question 5

what does slower GnRH release lead to?

Answer 5

Slower GnRH release leads to FSH release

Question 6

what triggers ovulation?

Answer 6

LH

Question 7

what stimulates follicle development?

Answer 7

FSH

Question 8

what releases GnRH and FSH/LH?

Answer 8

GnRH- hypothalamus

FSH/LH- anterior pituitary

Question 9

when is the follicular phase?

Answer 9

menstruation- ovulation (usually day 0- 14)

however follicular phase can vary in time

Question 10

what phase typically determines the length of a menstrual cycle?

Answer 10

Pre ovulatory phase (from the end of menstruation to ovulation) which is the follicular phase

Question 11

what happens in the ovaries during the menstrual phase?

Answer 11

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)

Question 12

what is happening to the uterus in the menstrual phase?

Answer 12

-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

Question 13

what are the 4 stages of follicular development?

Answer 13

1. Primordial follicles
2. Primary follicles
3. Secondary follicles
4. Antral/ Graafian follicles

Question 14

explain the structure of a follicle?

Answer 14

Oocyte surrounded by granulosa cells

Question 15

explain what is happening in the ovaries during pre ovulatory phase?

Answer 15

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

Question 16

what occurs to the uterus during the pre ovulatory phase?

Answer 16

-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)

Question 17

what day does ovulation occur?

Answer 17

day 14 in a 28 day menstrual cycle (14 days before menstruation)

Question 18

what occurs in the ovaries during ovulation?

Answer 18

-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

Question 19

what occurs in the uterus during ovulation?

Answer 19

-Progesterone and oestrogen continue to cause proliferation of the endometrium

Question 20

what/ when is the post ovulatory phase?

Answer 20

The luteal phase
-this is the most constant phase
-lasts 14 days with little variation (starting from day after ovulation- menstruation)