● The reproductive cycle in the `color{Violet}"female primates"` (e.g. monkeys, apes and human beings) is called `color{Violet}"menstrual cycle"`.

● The `color{Violet}"first"` menstruation begins at `color{Violet}"puberty"` and is called `color{Violet}"menarche"`.

● In `color{Violet}"human females"`, menstruation is repeated at an average interval of about `color{Violet}"28/29 days"`.

● The cycle of events starting from `color{Violet}"one menstruation"` `color{Violet}"till the next"` one is called the `color{Violet}"menstrual cycle"`.

● `color{Violet}"One ovum"` is released (ovulation) during the `color{Violet}"middle"` of each menstrual cycle.

● `color{Violet}"Menstruation"` only occurs if the released ovum is `color{Violet}"not fertilized"`.

● `color{Violet}"Lack of menstruation"` may be indicative of `color{Violet}"pregnancy"`.

● However, it may also be `color{Violet}"caused"` due to some other underlying causes like `color{Violet}"stress"`, `color{Violet}"poor health"` etc.

● The changes in the `color{Violet}"ovary"` and the `color{Violet}"uterus"` during menstrual cycle are induced by changes in the levels of `color{Violet}"pituitary and ovarian"` hormones.

● The secretion of `color{Violet}"gonadotropins"` (`color{Violet}"LH and FSH"`) increases gradually during the follicular phase, and stimulates `color{Violet}"follicular development"` as well as secretion of `color{Violet}"estrogens"` by the growing follicles.

● Both LH and FSH attain a `color{Violet}"peak level"` in the middle of cycle (about `color{Violet}"14th day"`).

● `color{Violet}"Rapid secretion"` of LH leading to its maximum level during the `color{Violet}"mid-cycle"` called `color{Violet}"LH surge"` induces `color{Violet}"rupture"` of the Graafian follicle and thereby the release of ovum (`color{Violet}"ovulation"`).

● After this, the `color{Violet}"remaining parts"` of the Graafian follicle transform as the `color{Violet}"corpus luteum"` .

● The `color{Violet}"corpus luteum"` secretes large amounts of `color{Violet}"progesterone"` which is essential for maintenance of the `color{Violet}"endometrium"`.

● The `color{Violet}"cycle starts"` with the menstrual phase, when `color{Violet}"menstrual flow"` occurs and it lasts for `color{Violet}"3-5 days"`.

● The menstrual flow results due to the `color{Violet}"breakdown"` of `color{Violet}"endometrial lining"` of the uterus and its blood vessels, which forms the `color{Violet}"liquid"` that comes out through vagina.

● This is the `color{Violet}"menstrual phase"`.

● The menstrual phase is followed by the `color{Violet}"follicular phase"` characterized by `color{Violet}"follicular development"`.

● During this phase, the `color{Violet}"primary follicles"` in the ovary grow to become a `color{Violet}"fully mature"` `color{Violet}"Graafian follicle"` and simultaneously the `color{Violet}"endometrium"` of uterus `color{Violet}"regenerates"` through proliferation.

● `color{Violet}"LH surge"` in mid cycle induces `color{Violet}"rupture"` of the `color{Violet}"Graafian follicle"` and thereby the release of ovum (`color{Violet}"ovulation"`).

● The `color{Violet}"ovulation"` (ovulatory phase) is followed by the `color{Violet}"luteal phase"` during which the remaining parts of the Graafian follicle transform as the `color{Violet}"corpus luteum"`.

● Such an `color{Violet}"endometrium"` (maintained by `color{Violet}"progesterone"` from `color{Violet}"corpus luteum"`) is necessary for `color{Violet}"implantation"` of the fertilized ovum and other events of pregnancy.

● During `color{Violet}"pregnancy"` all events of the menstrual cycle stop and there is `color{Violet}"no menstruation"`.

● In the `color{Violet}"absence"` of fertilization, the corpus luteum `color{Violet}"degenerates"`.

● This causes `color{Violet}"disintegration"` of the endometrium leading to `color{Violet}"menstruation"`, marking a `color{Violet}"new cycle"`.

● In `color{Violet}"human beings"`, menstrual cycles ceases around `color{Violet}"50 years"` of age; that is termed as `color{Violet}"menopause"`.

● Cyclic menstruation is an `color{Violet}"indicator"` of normal reproductive phase and extends between `color{Violet}"menarche and menopause"`.