Comparative Reproduction Menstraul Cycle Flashcards
What is menses/menstruation
When does it occur?
External loss of blood
Occurs after luteolysis at the beginning of the follicular phase
Which animal species show menstruation?
Apes
Old world monkeys
Average cycle length of a woman is how long
28 days
What are the 3 phases of the menstrual cycle?
1.14/15 day follicular phase; until Gonadotrophin surge is induced (called mid cycle surge)
2. 14 day luteal phase
3. Follicular phase again if pregnancy has not occured
What phase of menstrual cycle does menses occur
First few days of follicular phase
What are the 3 endometrial phases seen during menstrual cycle?
Menstrual phase
Proliferative phase
Secretory phase
(On anki)
During which endometrial phases are progesterone levels at their peak
During which endometrial phases are oestrogen levels at their peak
-Secretory phase
-Proliferative phase
Which endometrial phase do endometrium cells become fully grown and start secreting?
Secretory phase
What is function of progesterone during luteal phase of menstrual cycle
Stimulates repro tract & provides correct secretions for embryo
What occurs to the fully functional epithelial cells during menstrual cycle secretory phase if pregnancy does not occur
They start to shed; overtly expelled to the outside
What is menstrual flow
Endometrial tissues active and further grown in the secretory phase plus menstrual blood are expelled/ shed when progesterone is withdrawn at luteolysis (when pregnancy hasn’t occured- CL regression)
What are the hormone changes during menstrual cycle
Oestradiol starts rising in 2nd half of follicular phase and induces the mid-cycle LH surge
After ovulation progesterone rises due to CL development, and increased progesterone indicates the
luteal phase
The corpus luteum in the woman also secretes oestradiol (and inhibin A) which will suppress FSH
during the luteal phase
FSH rises after luteolysis (CL regression) at the onset of menses (=beginning of follicular phase, FP) which leads to a typical follicle wave emerging
DF dominant follicle selection occurs when?
At FSH decline, 1 week after luteolysis
How does dominant follicle stopnew follicular waves form occurring
Secretes Oestradiol and inhibin in the 2nd half of the FP suppressing FSH, so no new follicle wave
What are the similarities in the cow and mare menstrual cycle
Follicle dynamics, steroid function and CL lifespan very similar
Both show 2-wave & 3-wave cycles
Follicle dynamics:
Transient FSH rises—> follicle waves (major wave at beginning of follicular phase)—> selection of single dominant follicle
Role of steroids:
• oestradiol reduces FSH, induces GnRH surge
• progesterone reduces LH pulse frequency
CL lifespan 12-15 days
What are the differences in the cow and mare menstrual cycle
oestrous and menstrual cycles in the timing of follicle waves, the length of the follicular phase, and the CL function
CL function differences in:
• Secretion of inhibin A and oestradiol in addition to progesterone
• Luteolysis (passive = reduction in LH response leads to intra-luteal PGF2a and cytokine production causing apoptosis and autophagocytosis)
What is menopause in woman
When ovulation ceases. Occurs once the number of primordial follicles has depleted. Cessation of ovulation for >1 year= menopause
What age does menopause usually occur at?
51 years with range between 40-60years
What occurs several years before menopause occurs
decline in oestradiol and increase in FSH
What are side effects of menopause due to lack of Oestradiol/supplementation of Oestradiol
• osteoporosis
• cardiovascular disease
• side-effects of oestrogen therapy (HRT)
What is HRT
• oestrogen+progestogen (to reduce proliferative effects of oestradiol on uterus)
