A normal menstrual cycle refers to the regular physiological process that occurs in the female reproductive system, typically lasting approximately 28 to 35 days. It involves the monthly release of an egg from the ovaries, known as ovulation, as well as the shedding of the uterine lining, known as menstruation or a menstrual period.
What are the factors which is responsible for normal menstruation ?
1) Normal chromosomal pattern (46,XX)
2) Coordinated hypothalamo-pituitary-ovarian axis
3) Presence and patency of normal anatomical outflow tract
4) Endometrium is responsive to ovarian hormones which is oestrogen and progesterone
5) Active support from thyroid and adrenal glands
Menstruation is 3-5 days long and is process of shedding of endometrium to visible blood loss. But whole menstrual cycle is 28 days long normally.
Menarche :- Onset of menstruation for the first time in girls is known as menarche. Which occurs between 11-15 years with a median age of 13 years. Some time it can occur at 16 years in the case of delayed puberty.
Menopause :- Menopause is a complete cessation of menstruation due to abrupt cessation of follicular activity or unresponsive follicle. Menopause comes between the age of 45 to 50 years.
Reproductive or child bearing period :- It is a period between the menarche to menopause in which time normal female have regular menstruation.
Normal duration :- 21 to 35 days with mean duration of 28 days.
Oligomenorrhoea :- The term denotes the increased duration of menstruation. Where menses occurs prior to 35 days.
Polymenorrhoea :- The term denotes decreased duration of menstruation. Where menses occur before the 21 days.
Normal volume of blood :- 20 to 80 ml blood loss occurs at every cycle with average of 35 ml in every menstrual cycle. Here which 70% of blood loss occurs in the first 2 days.
Menorrhagia :- When the more blood loss occurs than the normal volume or duration is known as menorrhagia.
Metrorrhagia :- It is a condition where you find irregular intermenstrual bleeding which can be heavy or not so.
Normal menstrual discharge :- Dark altered blood, mucus, vaginal epithelial cells, fragments of endometrium, prostaglandins, enzyme and bacteria
In this blog we will discuss physiology of normal menstruation in brief and I will give detailed blog in short time.
Menstrual cycle has a two different types as per the different location of the cycle.
1) Ovarian cycles :- Ovarian cycle is a part where all the changes of the ovaries are shown like :-
• Recruitment of group of follicles
• Selection of dominant follicle and it's maturation
• Ovulation
• Corpus luteum formation
• Demise of Corpus luteum
This all changes are happen in two phases of 14 days.
• Follicular phase :- This phase is of 14 days. Which includes selection of dominant follicle and it's maturation. Recruitment of group of follicles occur 85 days prior to the respected cycles without influence of FSH. But selection of dominant follicle occurs in presence of FSH. With highest antral concentration oestrogen and lowest androgen : oestrogen ratio.
• Ovulation :- Ovulation occurs at sharp 14 days in normal female. Due to sustained rise in oestrogen for 24-48 hours produce LH surge from anterior pituitary which after sustained for 24-36 hours ovulation occurs. FSH is also increased during ovulation.
• Luteal phase :- Luteal phase is a ovarian phase after ovulation. Where maturation of corpus luteum occurs. And if fertilisation not occurs corpus luteum regress on the 22nd to 23rd of cycle. If fertilisation occurs than corpus luteum act as a reserved endocrine gland till 12 weeks and regressed at 24 weeks. Luteal phase is static phase and cannot be more or less than 14 days.
2) Endometrial cycles :- This cycles is occurs in a endometrial cavity that's why it is known as endometrial cycles. Endometrial responsiveness is very important in case of endometrial cycles. Oestrogen and progesterone is more important in endometrial cycles while gonadotrophins are more important in ovarian cycles. It covers the four stages :-
• Regenerative phase
• Proliferative phase
• Secretory phase
• Menstruation
• Menstruation :- It is the visible phenomena of normal menstruation. It is a periodic shedding of endometrium with degeneration and casting off of endometrium. Due to regression of corpus luteum and fall in the level of oestrogen and progesterone menstruation occurs. Usually menstruation is found in first five days of cycle.
• Proliferative phase :- It is usually found from 6 to 14th day of normal menstruation. Where proliferation of shedded endometrium occurs due to the rise in levels of ovarian oestrogens. In this phase glands becomes tubular and epithelium becomes columnar with proliferation.
• Secretory phase :- It is a phase after the ovulation. After ovulation there is marked increase in progesterone. And under the effect of it the endometrium becomes more and more vascular. And epithelium becomes more tall. Endometrium is now prepared for implantation and pregnancy. It is all occur in effect of corpus luteum. Once fertilisation not occurs till 22 to 23rd day. Corpus luteum started regressing and due to fall in level of ovarian hormones endometrium become degenerative and after that new cycle starts with menstruation.
Role of hormones :- It is very complex phenomenon to understand the role of hormones in normal menstrual cycle. But you can remember that in first half of the menstrual cycle FSH and Oestrogen are more in concentration and in second half LH and Progesterone are more. GnRH is stimulates the release of gonadotrophins from anterior pituitary. And thyroid and adrenal hormones are also work in coordination for normal and regular menses.
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