Repro8 - The Menstrual Cycle

Question 1

3 features of the early follicular phase of the menstrual cycle

Hormone Levels
FSH Levels
FSH Effects

Answer 1

1. ) Hormones Levels - no ovarian hormone production means low steroid and inhibin levels
2. ) FSH Levels - steadily rising because it is free from inhibition due to low steroid and inhibin levels
3. ) FSH Effects - binds to granulosa cells to continue follicular development until its capable of oestrogen and inhibin secretion
   - theca interna and externa cells also appear

Question 2

2 features of the mid follicular phase of the menstrual cycle

Function
Positive Feedback

Answer 2

1.) Function - nomination of a dominant follicle and prevention of recruiting new follicles

2. ) Positive Feedback - oestrogen now at a high enough conc to exert positive feedback –> LH surge
   - FSH keeps declining due to increasing inhibin levels having selective inhibition on FSH production by AP
   - low FSH prevents formation of new follicles

Question 3

3 features of the late follicular phase (preparation for ovulation) of the menstrual cycle

Oestrogen
LH
Progesterone

Answer 3

1.) Rapid Rise in Oestrogen - because oestrogen production is no longer dependent on FSH

2. ) LH Surge - helped by high oestrogen levels because they enhance its sensitivity to GnRH meaning:
   - the same stimulus produces a larger response

3.) Progesterone Production - begins as the granulosa cells become responsive to LH

Question 4

4 features of the luteal phase

Waiting Phase
Luteinised Follicle
LH Decline
Regression

Follicle
LH
Waiting

Answer 4

1.) Waiting Phase - further gamete development is suspended as the oocyte waits to be fertilised

2. ) Luteinised Follicle - due to the high levels of LH
   - secretes large amounts of oestrogen, progesterone, and inhibin.
3. ) LH Decline - suppressed by -ve feedback due to the presence of progesterone
4. ) Spontaneous Regression - in the absence of further rise in LH

Question 5

3 features of the ovarian cycle

Phases
Length
Ovulation

Answer 5

1. ) 2 Phases - follicular phase and the luteal phase
   - follicular phase is the development of the follicle
   - luteal phase is the presence of the corpus luteum
2. ) Length - lasts 28 (+/- 7 days)
   - luteal phase is always 14 days so variance in length depends on the follicular phase
3. ) Ovulation - release of the oocyte into the ampulla
   - occurs on roughly day 14

Question 6

3 phases of the uterine cycle

Answer 6

1. ) Menses (0-4) - this is the ‘period’
   - shedding of the endometrium

2.) Proliferative Phase (4-14) - endometrium responds to oestrogen by proliferating

3. ) Secretory Phase (14-28) - endometrium secretes various substances to prepare for implantation
   - glands produced in proliferative phase become secretory under the influence of progesterone

Question 7

5 features of the structure of the uterus and the changes of the uterus over the menstrual cycle

Answer 7

1. ) Structure - consists of endometrium and myometrium
   - endometrium divided into functional and basal layer
   - myometrium is the muscular wall
2. ) Early Proliferative - glands sparse and straight
3. ) Late Proliferative - functional layer doubles and glands become coiled
4. ) Early Secretory - endometrium reaches maximum thickness and very pronounced coiled glands
5. ) Late Secretory - glands have characteristic saw-tooth appearance

Question 8

3 outcomes of the ovulation

Answer 8

1. ) No Fertilisation - corpus luteum –> corpus albicans due to fall in LH –> dramatic fall in gonadal hormones
   - resorts back to -ve feedback and everything resets

2.) Fertilisation - syncytiotrophoblast produces hCG which exerts a luteinising effect, hCG is basically LH

3. ) Pregnancy - CL is supported by placental hCG so produces steroid hormones to support pregnancy
   - eventually, the placenta is capable of producing its own steroid hormones to control the HPO axis