Menstrual Cycle in Human
Cyclic changes occurring in the reproductive tract of females.
The reproductive period of the human female continues from about the age of about 12 years to 45 – 50 years.
This period is marked by a characteristic event repeated almost every month (28 days with minor variation) in the form of a menstrual flow (i.e., shedding of the endometrium of the uterus with bleeding).
It may be temporarily stopped only by pregnancy.
Menopause is stopping of ovulation and menses. Average age is 51 years. In this stage, woman lose the ability to reproduce.
Menstrual cycle is controlled by FSH, LH, estrogen and progesterone.
The period of a menstrual cycle is counted from the day of the onset of the flow to the next onset after 28 days.
This period can be divided into four main phases.
It lasts for 3 – 5 days during which blood is discharged out.
The bleeding is caused due to the shedding of the uterine lining rupturing the blood vessels which is mainly due to decrease of estrogen and progesterone secretion.
2. Follicular phase :
As the follicle grows it produces certain hormones which reactivate the uterine wall to become thickened and to be supplied with a lot of blood.
The thickening of endometrium occurs under the influence of estrogen hormone in association with progesterone.
This change is kind of preparation of die uterus to receive the fertilized egg and to provide for the development of the future embryo.
3. Ovulatory phase :
During this phase production of FSH decreases while that of LH increases which leads to ovulation on about the 14th day.
The follicle reptures and the released egg travel down the oviduct.
This phase helps in fertilization in the following ways, like:
- Uterine movements help in spread of sperms in female reproductive tract.
- Ciliary movements in the epithelium of fallopian tubes for bringing in the ovum.
4. Luteal phase / Secretory phase :
It lasts from 15 – 28 days. Uterus lining thickens further and becomes secretory.
This stage is meant for receiving the fertilized ovum (implantation).
Emptied follicle in the ovary turns into corpus luteum and supervised by LH of anterior pituitary.