The flow of blood along with endometrium cells of uterus and mucus through vagina is called menstruation. It is also called as menses, periods, chumps etc. It occurs around a regular interval of 28 days.
Cyclic menstruation is an indicator of normal reproductive phase and extends between menarche and menopause.
Onset of menstruation is known as menarche. It occurs between 10 – 14 years of age, when a girl attains puberty. Menarche, generally is considered as early, if it occurs before 9 years of age and late, if it occurs after 15 years of age.
Causes of Menarche
Age at which menarche occurs is affected by genetic and environmental factors.
Environmental factors include stress and photoperiod.
Other factors may include poor nutrition, several medical conditions like hypothyroidism, diabetes mellitus, congenital heart disease etc.
The cyclic changes in the reproductive tract of the female primates (monkey, apes and human beings), associated with the release of egg/ovum is called menstrual cycle. It usually lasts for about 28 days.
The menstrual cycle consists of four phases.
- Menstrual phase / Menstruation
- Follicular Phase / Proliferative Phase
- Ovulatory Phase
- Luteal Phase / Secretory Phase
It starts with menstruation / menstrual flow. Menstruation is the flow of blood along with cells from endometrial lining of uterus and mucus through vagina.
This phase usually lasts for 3 – 5 days. However, it differs from women to women. Some women have longer periods than others.
It only occurs when the ovum released is not fertilized. Lack of it may indicate pregnancy.
Hormonal Changes in Menstrual Phase
- Production of Lutenising hormone is reduced from the anterior lobe of pituitary gland.
- Production of hormone Progesterone from corpus luteum is reduced.
Hormone Progesterone is essential for maintenance of thickened endometrial lining of uterus.
FOLLICULAR PHASE/ PROLIFERATIVE PHASE
- Menstrual phase is usually followed proliferative phase. It lasts for about 14 days. End of this phase is marked with ovulation (Release of egg).
- Primary follicles in ovary grows to become fully matured graafian follicle.
- The endometrium(inner lining) of uterus denegrates.
Hormonal Changes in Follicular Phase
- GnRH (Gonadotropin Releasing Hormone) released by Hypothalamus signals the anterior lobe of pituitary gland to release gonadotropins -FSH (Follicular Stimulating Hormone) and LH (Luteunising Hormone).
- Level of LH and FSH increases gradually.
- FSH stimulates the ovarian follicles to secret oestrogen.
|Ovarian follicles are the several small sacs containing immature egg in ovary. These follicles are present in female body since the foetus is around 25 weeks old. When a female attains puberty, one immature follicle matures to become mature graafian follicle and releases egg/ ovum.|
- Ovulation is the release of mature egg/ovum from the ovary. This usually occurs on the 14th day of cycle (mid – cycle).
- Graafian follicle ruptures to release ovum
Hormonal Changes in Ovulation Phase
- Both LH and FSH attains a peak level in this phase.
- Secretion of oestrogen rises.
|Rapid secretion of LH leading to its maximum level during the mid – cycle is called LH surge.|
LH surge induces rupture of graafian follicle and thereby the release of ovum.
With the ovulation production of oestrogen stops.
SECRETORY PHASE/ LUTEAL PHASE
Ovulation is followed by luteal phase. It lasts for about 10 days. During this phase ruptured follicle transforms into a structure known as Corpus Luteum.
Hormonal Changes in Luteal Phase
- Large amount of Progesterone is released by corpus luteum.
- Small amount of oestrogen is also secreted.
In the absence of fertilization (pregnancy) corpus luteum degenerates causing the disintegration of endometrium, hence leads to menstruation which marks new menstrual cycle.
Complete cessation of menstruation in female is known as menopause. It occurs around the age of 50 years old.Posted on