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Physiology of menstrual cycle - Coggle Diagram
Physiology of menstrual cycle
Defination
Is a cyclic uterine bleeding under the influence of hormonal changes.
It occurs when the ovum is not fertilized (about 14 days after ovulation in a 28 day cycle).
Shedding of the lining of the uterus takes place causing blood to exit vagina.
This process last between five to seven days.
Ovarian cycle
Follicular phase
It is the oestrogen dominant phase with development of the Graafian follicle and oocyte and endometrium.
The follicular phase lasts about 13 to 14 days.
Follicle stimulating hormone influence the enlargement of mature ovum,
The ovary also secrete oestrogen at this stage.
The rising oestrogen levels in the blood stimulate growth of the endometrium and myomentrium of the uterus.
LH stimulates the dominant follicle to bulge from the surface of the ovary.
The Graafian follicle ruptures and discharges the secondary oocyte into the pelvic cavity where the fimbria guide it into the uterine tube.
The process called ovulation.
Luteal phase
This phase begins on the 15th day and lasts till the end of the cycle.
The Graafian follicle released during ovulation stays in the fallopian tubes for 24hours.
the cells of the ruptured follicle heals and forms a yellowish scar called corpus luteum.
The corpus luteum produces oestrogen and progesterone for approximately 2 weeks to develop the endometrium of the uterus.
If fertilization occurs, the corpus luteum continues to produce the necessary hormones until the placenta can take over this role.
Oestrogen levels remain high to stimulate the endometrium to thicken
If fertilization does not occur, the corpus luteum degenerates 14 days after ovulation and become corpus albicans.
Uterine cycle
Proliferative phase
During the follicular phase of ovarian cycle.
The increased levels of follicle stimulating hormone and oestrogen result in the proliferation of the endometrium.
Of which become thick with increased blood supply in readiness for reception of embryo if the oocyte is fertilized.
Crypts in the cervix are also stimulated to produce fertile cervical mucus that reduces the vaginal acidity creating more hospitable environment for sperm.
Secretary phase
This phase is marked by the endometrium reaching it peak thickening levels and vascularisation.
It is maintained by the production of luteanising hormone and progesterone by corpus luteum.
If fertilization does not occur the FSH, LH, oestrogen and progesterone levels decrease, the unfertilized oocyte disintegrates.
The endometrial layer becomes hemorrhagic and is shed in a process of menstruation.