Menstrual Cycle (Uterine cycle)
The average length of menstrual cycle is 28 days.
1. Menstrual Phase (1-4 days)
If the egg does not become fertilized as it travels down the fallopian tube on its way to the uterus.
Corpus luteum is degenerated and turn into corpus albicans.
Endometrium layer (lining of the uterus) is degenerates and shed and menstruation begins. Endometrium cells, blood from borken down capillaries and unfertilized ovum are passes through the vagina (birth canal), a process called menstruation.
2. Postmenstrual phase/ Preovulatory phase/ Proliferative phase/ Estrogenic phase
(6-12days)
Postmenstrual phase occurs between end of menstrual Phase and ovulation.
It usually includes day 6 to 13 or 14.
In this phase ovarian follicles is stimulated by FSH and growing towards maturity and is producing hormone estrogen (estrogenic phase).
Estrogen stimulate the proliferation of endometrium.
Ovulation
Rupture of mature follicle with expulsion of ova into pelvic cavity occurs on day 14 in 28 days cycle.
Ovulation occurs in overy at end of proliferative stage (day 14) due to LH hormone (trigger ovulation).
3. Premenstrual phase/ Postovulatory phase/ Secretory phase/ Progesterone phase
(15-28 days)
Length of premenstrual phase usually 25-28days in 28 days cycle.
Premenstrual phase occurs between ovulation and onset of menstrual Phase.
Corpus luteum secretes mainly progesterone, called progesterone phase.
Secretory phase, progesterone stimulates the endometrial glands to dilate, endometrial glands become cork-screw shaped, and filled with glycogen. They secrete a glycogen rich secretion during the secretory phase (after ovulation).
After ovulation LH hormone stimulate rupture follicle to develop corpus luteum, which produce progesterone.
Due to progesterone, thicking of endometrium layer; endometrium is transformed for implantation and secretory glands increased amount of watery mucus.
Rising progesterone levels inhibit LH release by anterior pituitary.
These changes in uterus are caused by progesterone, due to corpus luteum.
If fertilization and implantation not occur, the corpus luteum degenerates into corpus albicans and progesterone level fall.
Due to fall of progesterone level, endometrium lining broken and shed through vagina, called menstruation.
Menarche
Menarche is first begining of cycle of menstruation, known menarche.
Usually occurs average age of 12.
Menopause
Menopause is physiological cessation of menstrual cycles associated with advancing age.
Menopausal transition most often begins between ages 45 and 55.
The average age for menopause is age of 51.
Menopause is diagnose after 12 months since last menstruation.
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