What is menstrual cycle, Explain the ovarian changes taking place during menstrual cycle

– Refers to cyclical changes that takes place in the women
– Preparatory step for fertilization and Pregnancy
Duration – 25 – 35 Days
Average – 28 Days
Changes include:

  1. Ovarian Cycle
  2. Uterine Cycle
  3. Cervical Cycle
  4. Vaginal Cycle

#Ovarian Cycle

  • Follicular Phase
  • Ovulation
  • Luteal Phase

1. Follicular Phase
-Involves the development of a follicle
– One follicle matures each month
– During the lifetime of a female only 400 follicles mature
Stages of follicular development:
Primordial follicle → Primary Follicle → Secondary follicle → Tertiary follicle
(Involves addition of granulosa cells surrounding the oocyte & also formation of theca cells)→Antral follicle(Having fluid filled space) → Matured
Graafian follicle
2. Ovulatory Phase
The process of expulsion of secondary oocyte from ovary into peritonial cavity following rupture of mature graffian follicle
14th day of sexual cycle
Events of Ovulation

  • – Rapid swelling of follicle
  • – Formation of stigma
  • – Release of proteolytic enzymes
  • – Dissolution of capsular wall
  • – Rupture of graffian follicle

3. Luteal Phase ( 15th – 28th Day)
Events :
– Formation of corpus hemorrhagicum (ruptured follicle filled with blood)
– Formation of corpus luteum (clotted blood replaced with yellow colored lipid rich luteal cells)
– Formation of corpus albicans ( regression of corpus luteum)

#Uterine (Endometrial) Cycle

  • Menstrual (Bleeding) Phase
  • Proliferative phase
  • Secretory phase
1.Menstrual Phase

The lining of the uterus (endometrium) breaks down and is lost from the body. This is called menstruation or a period
Duration – Days 1-5
– 30 – 50 ml blood (75% Arterial)
– Ovum – unfertilized
– Mucus
– Endometrial debris – damaged endometrial tissue, serous fluid, a large amount of prostaglandins & fibrinolysin
Mechanism of menstruation
1. steroid production declines.
2. shrinking of endometrial tissue
3. reduction in blood flow to superficial layers – ischemic hypoxia & damage to
the epithelial and stroma cells & constriction of spiral arteries
4. Individual arteries re-open → tearing and rupturing the ischemic tissues.
5. Bleeding into the cavity
– About 50% of degenerating tissues is resorbed and 50% is lost as ‘menstrual bleeding’.

2. Proliferative Phase

– Days 6-13
– increase in estrogen causing the endometrium to thicken (from 1mm to 4 mm)
– angiogenesis
– stimulation of endometrial glands to grow

3.Ovulatory phase

-Day 14:
This occurs due to a sudden rise in LH secretion secondary to rise in oestrogen concentration .
(i) At about day 14 ovulation occurs and at this time cervical mucus increases in volume and becomes more watery, thus there may be a small vaginal discharge of watery cervical fluid.
(ii) The cervical mucus is thinnest at the time of ovulation and thus can easily be penetrated by spermatazoa than any other time.

4. Secretory Phase

Days 15-28 :
increase in progesterone causes
– endometrial thickness
– increased vascularity
– secretion of endometrial glands
(in preparation for the developing embryo)

   #                                  Cervical Cycle

1. Preovulatory Phase – Estrogen is predominant hormone
– Cervical mucus – Thin, Watery & Alkaline
2. Postovulatory Phase – Progesterone
– Cervical mucus – Thick & Tenacious

 #                                    Vaginal Cycle

1. Preovulatory Phase – Estrogen predominance
               Thick & Cornified Epithelium
2. Postovulatory Phase – Progesterone predominance
                  Thick & viscid secretion
                  Infiltrated with Leucocytes