Menstruation

 

 

 

 

Menstruation Cycle, Premenstrual syndrome.

 

Menstruation is a cyclic bleeding that occurs every month (26 to 30 days) throughout the child bearing period of about 30 years. A series of changes occur simultaneously in the ovaries and uterus (endometrium). These events are stimulated by the changes in the blood hormone levels   (of estrogens, progesterone, Follicle stimulating Hormone (FSH), Luetenizing Hormone (LH) ) etc.

 

Menstruation is a physiological process that occurs in the life of the female. The whole process is regulated by the hormonal levels.

 

Menstruation is also called as menses or periods.


The menses occuring for first time is referred to as “menarche”.
The average duration of each cycle of menstruation is about 28 days; but it may vary from woman to woman. The period of bleeding may last for average 5 days but again it may vary from 3 to 8 days.

 

DEFINITION


Menstruation is the process of cyclic bleeding occuring in females every 26 to 30 days throughout the child-bearing period of about 30 years.

 

The menstrual blood flow contains blood from capillaries, shed off epithelium and endometrial cells that line the uterus. It usually occurs in response to changes in the blood levels of hormones and caused in the case where the ovum is not fertilised and pregnancy or conception does not occur.


It is one of the normal physiological processes that occur on an average every 28 days and bleeding may last for the first 5 days of the menstrual cycle. However this duration may vary from woman to woman according to their blood hormone levels.

 

MENSTRUAL CYCLE

 

A series of events occuring simultaneously in the uterine wall (endometrium) and ovaries under the effect or regulation of  the blood hormone levels.


The hormones responsible are:-


Gonadotrophins: - 1) FSH (Follicle Stimulating Hormone)
                             2) LH    (Luetenising Hormone)


The FSH is responsible for the maturation of the ovarian follicles and the secretion of oestrogen leading to ovulation.


The LH is a hormone that stimulates ovulation and development of the corpus luteum as well as the secretion of progesterone.

 

Hypothalamus situated in the brain release the LHRH; which stimulates the anterior pituitary to secrete FSH and LH.

 

The menstruation cycle consist of 3 phases:-

 

  • Menstrual phase

 

  • Proliferative phase

 

  • Secretory phase

 

It is an on-going process and the cycle continues throughout the child bearing period.

 

  • Menstrual phase

 

It is considered as the phase of bleeding which lasts for 1 to 5 days (it may vary from 3 to 8 days).

 

Menstruation occurs when the ovum is not fertilised. The corpus luteum also starts to degenerate.


As a result, there is a fall in the levels of progesterone and oestrogen.


The endometrial layer of uterus highly depends on these ovarian hormones but due to decrease in their blood levels, the endometrium gets shed off and constitutes the menstrual blood flow, along with blood from broken down capillaries.

 

The falling levels of oestrogen and progesterone continue the anterior pituitary activity, so the levels of FSH start to rise and start another cycle.

 

PROLIFERATIVE PHASE

 

  • FSH stimulates the ovarian follicle and matures it. The production of oestrogen starts.

 

  • Under the effects of oestrogen, the functional layer of the endometrium proliferates and prepares itself to receive the fertilised ovum.

 

  • The endometrium grows; becomes thicker by rapid proliferation and also the blood capillaries and mucus secreting glands increases in number.

 

  • The ovarian follicle matures into a Graffian follicle which ruptures to release the ovum. This process is called ovulation.

With ovulation, the oestrogen production declines.

 

SECRETORY PHASE

 

  • In this phase, the LH stimulates the lining cells of the ovarian follicle to form the corpus luteum which then produces progesterone and some amount of oestrogen.

 

  • These hormones help in preparing the endometrium for reception of fertilized ovum.

 

  • The endometrium thus becomes thick, oedematous and the secretory glands produce increased amounts of watery mucus.

 

  • In case the ovum is not fertilised the endometrium is shed off and the blood capillaries are broken thus forming the menstrual blood flow. The corpus luteum also starts to degenerate.

 

Thus the menstrual phase starts and the cycle goes on.