Menstrual Cycle

Menstrual Cycle
Definition
In female human beings the reproductive cycle involves certain uterine changes which occur to prepare it for a possible pregnancy this ovarian cycle is called uterine cycle. This monthly egg saturation and uterine preparation is collectively called menstrual cycle or menses.

• Menstruation begins around the age of thirteen and stops at menopause at the age of fifty.
• Menstruation cycle is controlled by hormones.
• Menstrual cycle completes in 28 days.

Phases of Menstrual Cycle
Menstrual cycle completes in four distinct phases
1. Menstruation Or “M” Phase
2. Follicle Or “F” Phase
3. Ovulation Or “O” Phase
4. Corpus Luteum Or “L” Phase
1. Menstruation Phase

• When fertilization does not occur, the inner lining of uterus which because thickened and well developed to received fertilized ovum is broken.
• The progesterone hormone is stopped to secrete from the ovary.
• These broken tissues along with unfertilized ovum, mucus and blood are discharged out of the body through vagina its is called menstrual stage.
• When menstruation starts it is considered as the beginning of menstrual cycle.
• It lasts for 4 to 5 days during which menstrual flow occur.

2. Follicle Phase
The following events occur during this phase
a. Maturation of follicle
b. Endometrium Re Building

• This phase starts just after the menstruation and ends with the release of ovum.
• It lasts about 7 days (day 6 to 12)
• During this stage one or more ova start to develop.
• Only one follicle matures to produce an egg. This egg producing follicle is sometimes called Graffian follicle, while rest of follicle degenerates.
• This process initiated by FSH secrete by pituitary gland.
• FSH stimulates the ovary to produce a hormone called Oestrogen while oestrogen inhibit the secretion of FSH.
• Oestrogen take part in thickening the uterine wall.
• Low FSH level and high oesrogen level in blood initiates the secretion of LH hormone from the pituitary gland.

3. Ovulation Phase

• It is a short phase and is lasts in three days (13 to 15).
• During this phase graffian follicle of the ovary recaptures and the mature ovum is released. This process is called ovulation.
• Mature ova enters into the oviduct.
• This stage is initiated by the increase of LH level.

4. Corpus Luteum Phase
During this phase, following events occur
a. Formation of corpus luteum
b. Development of Endometrium
c. Feed back control

• This phase is the longest period of menstrual cycle.
• It lasts about 12-14 day (16 to 28).
• LH causes the ruptured follicle to change into a yellowish body called corpus luteum.
• Corpus luteum start producing another hormone called Progesterone.
• Progesterone enhances the growth of the mucous lining (endometrium) of the uterus.
• If the mature ovum, in oviduct is not fertilized, the Corpus Luteum gradually degenerates. Progesterone secretion stops and the internal lining of uterus gradually degenerates. Progesterone secretion stops and the internal lining of uterus disintegrates and sloughs off with blood.
• Menstruation begins and the cycle starts again.