Menstruation
Menstruation is a spontaneous cyclic (monthly) physiological shedding of internal lining of uterine cavity (endometrium) due to invisible interplay of female hormones. In simple terms, it is a regular monthly bleeding which a woman experiences. The first menstruation occurs usually at the age of 12 – 15 years. It is also called as 'menarche'. For the past couple of decades, the age of menarche is gradually declining with improvement of nutritious and environmental conditions.
Once, the menstruation starts, it continues cyclically at an interval of 22 - 35 days with a mean of 28 days.
Physiologically, it stops during pregnancy and lactation.
Ultimately, it ceases between the ages of 45 - 50 years when menopause sets in.
The duration of menstruation (menses) is about 4 - 5 days and the amount of blood loss is estimated to be 20 – 80 ml with an average of 50ml.
The menstrual discharge consists of mainly a dark altered blood, mucus, vaginal epithelial cell fragments of endometrium, prostaglandin, enzymes and bacteria.
Usually, at the midcycle, a mature egg is released (ovulation). If it gets fertilised, the menses ceases. Thus the absence of menstruation suggests that pregnancy has occurred.
Ovulation
Ovulation is a process by which a mature egg (mature Graffian follicle after secondary oocyte is released) is released from the surface of ovary to be available for fertilisation viz. conception.