QS Study

Menstrual cycle

Menstrual cycle means the monthly rhythmic changes in the rates of secretion of female hormones and corresponding changes in the ovaries and sexual organs as well known as a menstrual cycle. It is the hormonal procedure a woman’s body goes through each month to prepare for a probable pregnancy. It provides important body chemicals, called hormones, to keep you healthy. It also prepares your body for pregnancy each month.

The average length of each cycle: 28 ± 1 day. (Normally)

Phases of the menstrual cycle: 3 phases –

  • Proliferative phase -10 days (5th – 14th day)
  • Secretory phase -14 days (15th – 28th day)
  • Menstrual phase – 4 days (1st – 4th day).

Fig: Menstrual cycle

Changes in different phases of menstruation:

(A) Proliferative/Estrogen phase: Under the influence of estrogen secreted by theca and granulosa cells of developing follicles, the following changes takes places.

  • Re-epithelization of the endometrium.
  • The glands and blood vessels become elongated and tortuous and irregular.
  • Stromal cells and epithelial cells at the basal part begin to proliferate.
  • Endometrium becomes 3-4 mm thick.

These phases are known as a preovulatory phase.

(B) Secretory/Progesterone phase:

Under the influence of progesterone secreted by corpus luteum, a small amount of estrogen following changes takes place.

(i) More proliferation of endometrial stromal cells and glandular cells,

(ii) Blood vessels become more tortuous and elongated,

(iii) Endometrium becomes 5-6 mm thick –

  • Superficial compact layer,
  • Intermediate spongy layer,
  • Basal layer with the straight gland.

(C) Menstrual/bleeding phase: The periodic shedding of blood, a damaged tissue of the endometrium and unfertilized ova per vagina are called menstruation.

Mechanism:

(i) Degeneration of corpus luteum,

(ii) Hormonal support progesterone, estrogen sharply fall down,

(iii) Constriction of the spiral artery which supplies the stratum functional,

(iv) Stratum functional become ischemic,

(v) Wall of the spiral artery become necrotic,

(vi) Necrotic wall ruptures and initiates menstrual bleeding.li

Related Study: