Menstruation and different phases of Menstrual cycle – The course is designed for the basic understanding of anatomical structures and physiological functions of human body, musculoskeletal system, digestive system, respiratory system; cardiovascular system; urinary system, endocrine system, reproductive system, nervous system, hematologic system, sensory organs, integumentary system, and immune system.The aim of the course is to acquire knowledge and skills regarding anatomy and physiology.
Menstruation and different phases of Menstrual cycle
Menstrual cycle:
The reproductive system of women shows regular cyclic changes that may be regarded as periodic preparation for fertilization and pregnancy. This cycle is Menstrual cycle.
Duration: Average 28 days.
(It may be as short as 20 days or as long as 45 days even in normal woman).
Menstruation:
Menstruation is the periodic vaginal bleeding that occurs with the shedding of the uterine mucosa along with uterine glands and blood vessels due withdrawal of ovarian hormone.
Or,
Menstruation is the monthly cyclical desquamation of the endometrium. It is caused by the reduction of estrogen and progesterone (especially progesteron) at the end of the monthly ovarian cycle.
- Menarche is the first menstrual cycle, or first menstrual bleeding, in female.
- Menopause is complete cessation of menstrual cycle
(Ref: Guyton and Hall 12th 995p. + Ganong 23 411p.)
The phases of Menstrual cycle are –
A. Menstruation phase (Ist to 4th day)
B. Proliferative phase (5th to 14th day).
C. Secretory phase (15th to 28th day).
A. In menstruation phase:
Sudden reduction of estrogen & progesterone causes shedding of uterine mucosa known as menstruation
1. The onset of menstruation, the tortuous blood vessels become vasospastic due to release of prostaglandins.
2. The vasospasm and loss of hormonal stimulation causes necrosis of the endometrium.
3. As a result, blood at first seeps into vascular layer of endometrium and hemorrhagic areas develop more rapidly.
4. Then, the necrotic outer layer of the endometrium gradually separate from the uterus at the site of the hemorrhage and thereby menstruation occur.
Duration: 1st to 4th day of menstrual cycle.
B. In proliferative phase (estrogen phase)-
1. At the beginning of each monthly cycle, most of the endometrium is desquamated by menstruation.
2. The endometrial surface is re-epithelized within 4 to 7 days after the beginning of menstruation, under the influence of estrogen.
3. Here, the thickness of endometrium increases and endometrial gland & blood vessels grow progressively.
Duation: 5th to 14th day of menstrual cycle.
C. In secretory phase (Progestational phase):
1. This phase is after ovulation, under the influence of progesterone.
2. The endometrium become edematous, more vascular and lipid & glycogen deposition increase within the stromal cells.
3. The endometrial glands become coiled, tortuous and increase their secreting activity.
Duration: 15th to 28th day of menstrual cycle.
(Ref: Guyton & Hall, 12th edition, P-995+ Hyde, J.S., & DeLamater, J.D. (2006). Understanding human sexuality. New York: McGraw-Hill)
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