Menstrual cycle part-2 Class 12th chapter-3 by Anshul sharma

Menstrual cycle
" The reproductive cycle in female primates like monkey apes and humans is called menstrual cycle."
" The cyclic events starting from one menstruation flow till the next one is called menstrual cycle."
The cycle repeat after 28 days and normally one egg ( secondary oocyte) is released per cycle.
Menstruation- menstruation is the process by which blood mucousal tissue are discharge from the inner lining of uterus through vagina. It is also known as periods.
Composition of menestrual discharge- it contains- blood(30-40ml), unfertilized egg(secondary oocyte), mucous, striped endometrium, WBC.
Menstruation is absent- before puberty, during pregnancy, after menopause.
Menarche- menarch is the first menstruation for a human female. It generally begins at puberty. The actual age for menarche varies from person to person. Menarche signal the beginning of reproductive phase of female.
Menopause- " menopause is the permanent ceasing of menstrual cycle in female due to age" the age of menopause vaaries from person to person. The average age of menopause is between 45-50yrs.
Amenorrhoea- absence of menstruation
Oligomenorrhea- scanty blood flow during menstruation
Polymenorrhea- excess blood flow during menstruation.
Phases of menestrual cycle- menstrual cycle follow three phases-
I. Menestrual phase
II.Follicular phase
III. Luteal phase
During menstrual cycle characteristics changes occurs in ovary and uterus lining( endometrium). These changes are controlled by FSH, LH, OESTROGEN, PROGESTERONE.
I.Menestrual phase- this is the period of menstruation when the menestrual flow occurs.
It occurs when the ovum released by the ovary is not fertlized. Lack of menstruation may indicate pregnancy.
Menstrual flow may also be affected due to stress, poor diet, poor health and some medicine.
It typically last for 3-5 days.
There is breakdowns of the endometrial lining of the uterus and it's blood vessels which form a liquid that come out of the vagina.
II. Follicular phase- this is the phase of maturation of ovarian Follicle.
The level of gonadotropin ( LH& FSH) gradually increase through the follicular phase.
The increased level of LH and FSH stimulate follicular development. The primary follicle in the ovary grow to form a fully mature graffian Follicle. FSH also stimulate the secretions of OESTROGEN by the growing follicle.
Under the influence of OESTROGEN the endometrium of the uterus regenerate through proliferation.
Ovulation- the level of FSH and LH reach peak at mid- cycle around 14th day. The rapid increase in LH level at mid cycle leading to maximum LH level mid cycle is called as the LH surge. LH surge induce the rupture of garffian Follicle and there by release of ovum( sec. Oocyte)
" The process by which am ovum is released by a graffian Follicle from the ovary. It is a result of LH surge which occurs mid cycle around 14th day"
III. Luteal phase- "this the phase of formation of corpus luteum"
Under the influence of LH the remaining part of garffian Follicle after ovulation form the corpus luteum.
Corpus luteum is a temporary endocrine gland that secret progesterone which is essential for the maintenance of endometrium.
The endometrium is necessary for implantation of blastocyst and other events of pregnancy.
In absence of FERTILIZATION or pregnancy the corpus luteum degenerate at 28th day of menestrual cycle. This results in low level of progesterone.low level of progesterone causes breakdowns of endometrium leading to the menestruration and thus starts a new cycle.