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 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 – Expulsion 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]

Download the App: Android App

For more Lectures, please visit-

YouTube Channel – NursingLecture

Facebook – Facebook Page