what is Menstrual Cycle

What Is Menstrual Cycle

During the reproductive period of a female (30 - 33 years) the female reproductive tract undergoes a series of cyclic changes which are meant to prepare them for pregnancy and collectively form the menstrual cycle.

• The average length of menstrual cycle in human female is 28 days.
• It is absent during pregnancy, before menarche (Appearance of first MC) and after menopause (Cessation of MC).
• This cycle can be divided into four phases. The 4 phases are

The menstrual (destructive phase)

The proliferate (follicular) phase

The adulatory phase

The secretory (luteal) phase

The cyclic reproduction changes of the human female are marked by menstruation, during which some cells, uncloatted blood from ruptured blood vessels, other fluids and uterine endometrium are released through the cervix and vagina. Each menstrual cycle occurs about every 28 days and last for 4 - 5 days. The menstruation occurs 12 to 14 days after the ovum is released from the ovary (ovulation), about once in four weeks. The periodicity of cycle varies with individuals. After fertilization, menstruation ceases and it is the first indication of pregnancy.

FOLLICULAR PHASE / POST MENSTRUAL PHASE:

It lasts about 10 -12 days and starts from 5 ^th to 14 ^th day.

• FSH hormone secretion increases from pituitary.
• FSH stimulates change of primary follicle to graafian follicle.
• Follicular cells secrete estrogen hormone.
• It stimulates growth and maintenance of secondary sex organs.
• Endometrium (inner lining) of uterus becomes thicker as it prepares itself for implantation.
• Fallopian tubes become thicker.
• FSH secretion decreases and LH secretion increases.

OVULATORY PHASE:

It occurs on 15 ^th day (midway between two menstrual cycles).

• Ovum leaves ovary and received by fallopian tube.
• Ovum remain viable for two days.
• LH level increases in blood to control ovulation.
• Due to LH Graafian follicles change into corpus luteum (yellow body.)

LUTEAL PHASE:

It extends from 16 ^th to 28 ^th day.

• Corpus luteum increases in size and secretes progesterone.
• FSH and LH secretion decreases to stop ovulation.
• Uterine endometrium proliferate to become 5 mm. thick.

MENSTRUAL PHASE:

It extends from 1 ^st to 4 ^th day.

• If ovum remains unfertilized corpus luteum start degenerating.
• Level of progesterone in blood decreases.
• The unfertilized ovum along with uterine epithelium, about 50-100 ml of blood and some mucus is expelled out through the vaginal orifice and is called menstrual flow.