Physiology of Menstruation

Menstruation (Greek Word, men – month) is monthly uterine bleeding outflowing through vagina onto vulva for 4-5 days every 28 days during reproductive life of a women from menarche to menopause. Menses are normal uterine function whereby endometrium prepares to receive pregnancy.

Bleeding comes from oestrogen progesterone primed endometrium. Woman gets 13 menses in a year and around 400 menses in her reproductive life.

The menstrual cycle of 28 days starts on day of onset of menstruation (day 1) and ends at day 28 on start of next mens.

Menstruation signals that fertilization and embedding of fertilised ovum have not occurred on the preceding menstual cycle. Anovular menstruation is cyclical monthly bleeding from only oestrogen primed endometrium. This occurs for a few years after onset of menstruation (menarche) and before final cessation of menstruation (menopause).

Normal menstruation

Clinical features

Menstruation is normal body function. Most women get only vaginal bleeding for 3 5 days with no discomfort. However around one quarter women get menstrual discomforts menstrual molimina. These discomforts do not interfere with usual day’s activity. Only 5 10 percent develops during some part in their about 30 years menstrual life painful mens interfering day’s activities (dysmenorrhoea). The menstrual molimina are as :


1. Feeling of heaviness and discomfort in the pelvis, lower abdomen and in the small of the back.

2. Feeling of pricking and fullness in the breasts.

3. Frequency of urination and constipation.

4. Feeling of lassitude, irritability, and headache. Above symptoms vary in severity from individual to individual. Rarely, bleeding from nose may occur as vicarious menstruation’ since blood viscosity falls at mens.


1. Sudden drop in temperature of about 1 degree F but with individual variations.

2. Pulse rate and blood pressure tend to drop.

3. Gain in weight occurs during premenstrual fortnight upto about 1 Kg. due to retention of water and salt; it occurs in about half of women. There is loss of weight with the onset of flow.

4. Menstrual loss (mens). The vaginal menstrual bleeding mainly arterial, partly venous is a dark reddish liquid (not clotted) blood with shed endometrial tissue bits. The discharge has disagreeable smell due to the secretion of vulvar sebaceous glands and decomposition of blood elements. Menstrual blood is deficient in prothrombin, and fibrinogen but rich in calcium. Microscopically, it contains red cells, large number of leucocytes, vaginal epithelium, cervical mucus, fragments of endometrium with macrophages, histiocytes, mast cells and bacteria, Menstrual discharge also contains cholesterol, oestrogen, lipids and prostaglandins. Menstrual blood from the endometrium clots in the uterine cavity by its thromboplastic property. The clots are dissolved by the fibrinolysins released from the endometrium. Fibrin degradation products therefore circulate in increased amount during menstruation. Clots are passed when mens¬trual bleeding becomes excessive.

Interval and Duration

The menstrual cycle lasts on an average twenty eight days. A deviation of 2 to 3 days can be frequently encountered. The extremes of 21 and 35 days interval may also be found. In any woman’s menstrual life, the interval can vary. The usual duration is three to five days with essentially normal extremes of two and seven days. Every woman needs sex education in this normal range of menstrual pattern so that she does not suffer from miseducation on normal menstrual pattern taken as menstrual irregularity.

Blood Loss

The average total blood loss during menstruation has been estimated as 35 ml (range 5 60 ml); average loss of iron was found as 12 mg. A rough clinical estimate is that normally not more than three fresh pads are necessary in the twenty four hours two during the day and one at night, thus requiring total 12 15 pads during a rnens. This loss widely varies and becomes greater in women living in warm climate than those living in cold climate.


Proper education on mens is important. She should be educated that menstruation is not the drainage of noxious substance from the body but a normal manifestation of womanhood. During menses, she should carry on her usual activities including daily bathing, playing games. Personal hygiene is maintained by changing regularly sanitary pads. Intravaginal tampons can be used by the married provided she does not forget to leave it behind. Healthy couple can have sexual intercourse during menses. Postponement or advancement of menstruation. This becomes at times necessary for important social reason like marriage. This is not to be advocated on flimsy ground. The hormone therapy employed is the following:

1. Progesterone norethisterone one tab. thrice daily starting from 20th day of menstrual cycle till beyond the date of postponement.

2. Oestrogen progestogen contraceptive pills, two a day is started from the 20th day. Menstrual flow is expected 2 to 3 days after the treatment is suspended. Menstruation can be pre¬maturely brought by starting hormone therapy from 5th day of mens for 14 days, The therapy is (a) Oestrogen ethinyl oestradiol 0.05 mg. t.d.s. or (b) Oestrogen progestogen oral pill once daily. Anovulax menstrual flow is likely to begin within 2 3 days of the cessation of therapy.

Endocrine mechanism of menstruation

Play of sex hormones from hypothalamus in brain, anterior pituitary gland, ovary causes menstrual bleeding from uterine endometrium.

This is called hypothalamus- pituitary-ovarian-uterine axis

Steps are-

1. In the brain, hypothalamus acts as switch to endocrine mechanism of menstruation and starts the process by secreting gonadotrophin releasing hormone (GnRH) or (LHRH) by peptidergic neuron. The latter is controlled by aminergic neuron. Environment influences menstruation via cerebral cortex and hypothalamus.

GnRH flows down from hypothalamus via pituitary portal vessels to

2. Anterior pituitary gland (gonadotroph cells) liberating follicle stimulating Hormone (FSH) and Luteinising hormone (LH) in blood circulation to initiate growth of ovarian follicles in both ovaries.

Ovarian Cycle. Ovarian follicles (20 in number) are grown in a menstrual cycle in three steps.

(a) ovarian Follicles are grown from primordial follicles. A single graarian follicle matures and becomes dominant by effect of FSH while other follicles undergo atresia.

(b) Oestradiol is secreted by maturing ovarian follicle in the circulation ‘ stimulates hypothalamus and anterior pituitary to cause surge of LH and FSH hormones in blood (Positive feed back) on day 12 of menstrual cycle.

(c) Ovulation (discharge of ovum from ovary) occurs on day 14 of menstrual cycle. Corpus luteum (yellow body) is formed in the shell of mature graafian follicle ovulation due to LH effect.

Corpus luteum remains mature From day 19-26, degenerates on day 27 and 28 if no pregnancy occurs in menstrual cycle’. Plasma prolactin (from anterior pituitary) rises (luring luteal phase and appears to maintain corpus luteum. Copious progesterone hormone., some oestradiol and inhibin (peptide hormone) are secreted by corpus luteum. Oestradiol causes luteolysis while inhibin depresses FSH.

Uterine cycle

(a) Proliferative phase

Oestradiol from ovarian follicles causes proliferative changes in uterine endometrium (day 7-14). All the endometrial tissue elements of I mm thick proliferate. Prior to start of proliferative phase, repair phase. runs with mens bleeding and ends by 48 hours after mens.

(b) Secretory phase. Progesterone (from corpus luteum) causes secretary changes in endometrium (day 15 – 26 to receive fertilised ovum for embedding. Glycogen appears as subnuclear vacuoles in endometrial gland followed by secretion of glycogen and mucus on the lumen of gland. Glands become Corkscrew . Endometrial vessels become coiled, stroma becomes vascular and oedernatous. Endometrium thickens to 5 mm into three layer (a) superficial compact layer with neck ot’glands (b) spongy layer with dilated glands (c) basal layer in contact with myometrial layer.

Stage of regression occurs in secretory endometriurn on day 27 to 28.

(c) Menstrual bleeding phase occurs for 4 – 5 days after day 28 of the cycle due to shedding away of endometrial bits and bleeding from endometria I bed. Necrosis and shedding of endometrial bits extend from region to region during first 2 days of menses. Bleeding occurs as (a) capillary bleeding with or without the formation of subepithelial haematoma (b) venous haemorrhage and (c) diapedisis.

Menstrual phase is caused by withdrawal of oestradiol and progesterone support to endometrium.. FSH rises again to start another, cycle.

Cause of menstrual bleeding. Exact cause is still obscure. The sequence of events are :

Withdrawal of oestrogen and progesterone due to degeneration of corpus luteum ‘rapid shrinkage and regression of secretory endometrium overcoiling of endometrial spiral arterioles ‘ stasis of circulation in the functional layer of endometrium ‘ necrobiosis of vessels. Prostaglandins elaborated by endometrium also cause vasospasm of spiral vessels ‘ ischaemic necrosis of bit of endometrium suppfied by spiral artery relaxation of spiral vessel bleeding from spiral vessel end. These vascular changes are described by Markee (1940)

In the shedding process clotting and fibrinolysis at bleeding site occur so that unclotted dark red blood with endometrial tissue bits are discharged for 4-5 days. Dating of endometrium. Endometrium is dated from its histological appearance particularly during secretory phase e.g. prenuclear vacuoles – 16th day, basal nuclei, secretion in gland lume – 20th day.

Immobilienmakler Heidelberg

Makler Heidelberg

Source by Tapan Pal