Female Reproductive Cycle [Menstrual Cycle]

A duration of 28 days in the female reproductive cycle is divided into 4 phases –
– Menstrual Phase
– Preovulatory Phase
– Ovulatory Phase
– Post-Ovulatory Phase

(A) Menstrual Phase [ First 5 days of the cycle / menses=month / Menstruation]

As the Influence of FSH (Follicle stimulating hormone)

Primordial follicles develop & then into

Primary follicles & then change into secondary follicles in the ovaries
(A follicle that begins to develop in a particular cycle may ovulate after several cycles later)

Menstrual flow is about 50-150 ml occurs through the uterus

as a decline in progesterone & estrogen level

which causes the release of prostaglandins

Arterioles become constrict & O2 deprived cells begin to die

Stratum functionalis ( functional layer) sloughs off

(B) Preovulatory Phase [Proliferative Phase]-

[ Time between the end of menstruation & ovulation / 6-13 days in 28 days cycle]

secondary follicles secrete estrogen (1 from both ovaries)

Become dominant follicle

Estrogen decreases secretion of FSH by dominant follicles

stop the growth of other follicles

One mature dominant (Graafian follicle) continue to enlarge (>20 mm in diameter)

 estrogen within the follicle stimulate and  repair of the endometrial wall

Mitosis in the cells of stratum basalis & produce a new stratum functionalis (4-10 mm diameter)

(C) Ovulation – [Rupture of Graafian follicle & release of 2˚ oocyte, on the 14th day of cycle]

 High level of estrogen in the last part of the pre-ovulatory phase

Exert positive feedback on a cell that secretes LH & GnRH ( Gonadotropin-releasing hormone )

GnRH promote the release of FSH & LH by the anterior pituitary

LH causes rupture of the Graafian follicle

Note – Explusion of 2˚ oocyte about 9 hours after the peak of the LH surge.

(D) Post Ovulatory Phase –

[ Secretory Phase / Luteal Phase / Time between the ovulation & onset of next menses / from 15-28 days in a 28-day cycle.]

 After ovulation mature follicle collapses

Basement membrane between granulosa cell & theca cell breaks down and change into  corpus luteum

Corpus luteum secretes progesterone, estrogen, relaxin, inhibin [Luteal phase]

* If 2˚ oocyte not fertilized corpus luteum has a lifespan of 2 weeks, becomes corpus albicans

Progesterone, estrogen, inhibin decreases & GnRH, FSH & LH increases due to loss of negative feedback suppression by ovarian hormones

*  If 2˚ oocyte fertilized

Corpus luteum persists past its normal 2-week life span

Rescued from degeneration by hCG

hCG (Human chorionic gonadotropin) produced from chorion of an embryo after the 8th day of fertilization

Progesterone, estrogen produced by corpus luteum promote the growth of the endometrial gland

Secretory activity of endometrial gland increases

which secretes glycogen [in secretory phase for the nourishment of fetus]

Share via
Copy link
Powered by Social Snap