The sexual cycle average 28 days in length.
Sexual cycle consist of series of changes that take place in ovaries and uterine wall.
Sexual cycle occur in two phase that are interrelated cycle;
1. Ovarian cycle
Event occurs in ovaries.
2. Menstrual cycle
Occurs in changes in uterus.
Role of Hormone
Hormones of hypothalamus and anterior pituitary regulate overies.
Hormones of ovaries regulate uterus.
Hypothalamus
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Pituitary gland
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Ovaries
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Uterus
Hypothalamus secretes GnRH (Gonadotropin releasing hormone). GnRH stimulate anterior pituitary to secrete;
1. Follicle stimulating hormone (FSH)
2. Luteinizing hormone (LH)
1. Follicle stimulating hormone (FSH)
It stimulates maturation of ovarian follicles and secretion of estrogen, leading to ovulation.
2. Luteinizing hormone (LH)
It stimulates the development of corpus luteum and secretion of progesterone.
Hormones secreted in cycle are regulated by feedback mechanism.
Ovarian Cycle
Ovarian cycle occurs in two phases;
1. Follicular phase
2. Luteal phase
Ovarian cycle repeat at intervals of 28 days, with ovulation occuring mid cycle (on day 14).
1. Follicular phase
Follicular phase is the period of follicle growth, considered from first to 14th day of cycle.
In ovaries there are several follicle at different stages of maturation.
1. Primordial follicle
Primordial follicle becomes primary follicle.
2. Primary follicle
Primary follicle becomes secondary follicles.
3. Secondary follicle
Secondary follicle turn into graafian (mature) follicle.
In ovarian phase estrogen is secreted by ovarian follicles (graafian follicle).
Ovulation
Ovulation is release of an oocyte, occurs on day 14th. Ovulation occurs when reputure follicle and expel secondary oocyte into peritoneal cavity.
When ovulation occurs, some women experience pain in lower abdomen caused by intense stretching of ovarian wall during ovulation, known as mittelschmerz (ovulation pain).
If more than one oocyte ovulated, can be result in multiple birth.
After ovulation the egg lives for 12 to 24 hours in uterine tube, at this time must be fertilised to become pregnant.
2. Luteal phase
Luteal phase started when wall of graafian follicle rupture. The ruptured follicle is then turned into corpus luteum.
Progesterone hormone is secreted by corpus luteum.
After ovulation released oocyte enters uterine tube, where it will be fertilized or discarded.
If pregnancy not occur, corpus luteum starts degenrating and reminas scar called corpus albicans.
If fertilization and implantation occur, about 7-8 days after fertilization, release of human chorionic gonadotropin (HCG) hormone.
Human chorionic gonadotropin (hCG) is a hormone that can be detected in urine and blood when pregnant.
2. 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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