• Menstrual cycle --It is the manifestation of cyclic events that take place in a rhythmic fashion during the

reproductive period of a woman’s life.it starts at the age of 12 to 15 years, which marks the onset of puberty.
 The commencement of menstrual cycle is called menarche It ceases at the age of 45 to 50 years.
 Permanent cessation of menstrual cycle in old age is called menopause.
 It is usually 28 days. But, under physiological conditions, it may vary between 20 and 40 days.
• CHANGES DURING MENSTRUALCYCLE--During each menstrual cycle, series of changes occur in ovary and accessory sex organs.
 Ovarian changes, Uterine changes, Vaginal changes, Changes in cervix. All these changes take place simultaneously.
• Changes in the ovary during each menstrual cycle occur in two phases:
A. Follicular phase B. Luteal phase.
• Follicular phase – It extends from the 5th day of the cycle until the time of ovulation, which takes place on 14th day. Maturation
of ovum with development of ovarian follicles takes place during this phase. Ovarian follicles are glandular structures present in
the cortex of ovary. Each follicle consists of the ovum surrounded by epithelial cells, namely granulosa cells. The follicles
gradually grow into a matured follicle through various stages.
 Primordial follicle Primary follicle Vesicular follicle Matured follicle or Graafian follicle
• Primordial follicle --At the time of puberty, both the ovaries contain about 400,000 primordial follicles .Each primordial follicle has an ovum,
which is incompletely surrounded by the granulosa cells . These cells provide nutrition to the ovum during childhood. Granulosa cells also
secrete the oocyte maturation inhibiting factor, which keeps ovum in the immature stage. All the ova present in the ovaries are formed before
birth. No new ovum is developed after birth. At the onset of puberty, under the influence of FSH and LH.
• Primary Follicle- Proliferation of granulosa cells and increase in size of the follicle
ii. Increase in size of the ovum, ii. Onset of formation of connective tissue capsule around the follicle.
Primary follicles develop into vesicular follicles.
• Vesicular Follicle-- .
Changes in granulosa cells, Changes in ovum, Formation of capsule.
• The covering sheath is known as follicular sheath or Theca folliculi.
It divides into two layers:
a. Theca interna b. Theca externa
• Graafian follicle – It is the matured ovarian follicle with maturing ovum.
Changes taking place during the development of Graafian follicle---
 Size of the follicle increases to about 10 to 12 mm. It extends through the
whole thickness of ovarian cortex
 At one point, the follicle encroaches upon tunica albuginea and protrudes
upon surface of the ovary. This protrusion is called stigma. At the stigma,
the tunica albuginea becomes thin
 Follicular cavity becomes larger and distended with fluid-
 Ovum attains maximum size
 Zona pellucida becomes thick
 Corona radiata becomes prominent
 Small spaces filled with fluid appear between the cells of germ hill, outside
the corona radiata. These spaces weaken the attachment of the ovum to the
follicular wall
 Theca interna becomes prominent. Its thickness becomes double with the
formation of rich capillary network
• On the 14th day of menstrual cycle, Graafian follicle is ready for the process
of ovulation.
OVULATION---The Graafian follicle in the ovary ruptures and
the ovum is released into the abdominal cavity. Ovulation occurs on
the 14th day of menstrual cycle in a normal cycle of 28 days. LH is
responsible for ovulation. Prior to ovulation, large amount of LH is
secreted. This causes changes in the Graafian follicle leading to
ovulation.
Stages of Ovulation--
 Graafian follicle moves towards the periphery of ovary
 New blood vessels are formed in the ovary by actions of LH and
progesterone
 These blood vessels protrude into the wall of the Follicle
 This increases the blood flow to the follicle
 Now, prostaglandin is released from granulosa cells of the
follicle
 It causes leakage of plasma into the follicle
 Just before ovulation the follicle swells and protrudes against
the capsule of the ovary. This protrusion is called stigma.
 Then, progesterone activates the proteolytic enzymes present in
the cells of theca interna
 These enzymes weaken the follicular capsule and cause
degeneration of the stigma
 After about 30 minutes, fluid begins to ooze from the follicle
through the stigma
 It decreases the size of the follicle causing rupture of stigma
 Now, ovum is released from the follicle along with fluid and
plenty of small granulosa cells into the abdominal cavity
• LUTEAL PHASE- It extends between 15th and 28th day of menstrual cycle. In this phase, corpus luteum is
developed and hence this phase is called luteal phase.
• Corpus Luteum– It is a glandular yellow body, developed from the ruptured Graafian follicle after the release of
ovum. It is also called yellow body.
• Development of Corpus Luteum- After the rupture of Graafian follicle and release of ovum, the follicle is filled
with blood. Now the follicle is called corpus hemorrhagic. The blood clots slowly. Corpus hemorrhagic does not
degenerate immediately. It is transformed into corpus luteum. Follicular cavity closes gradually by the healing of
the wound. Blood clot is gradually replaced by a serous fluid containing fibrin.
Functions of Corpus Luteum
Secretion of hormones--Corpus luteum acts as a temporary endocrine gland.
It secretes large quantity of progesterone and small amount of estrogen. Granulosa lutein cells secrete progesterone and theca
lutein cells secrete estrogen. LH influences the secretion of these two hormones.
Maintenance of pregnancy--If pregnancy occurs, corpus luteum remains active for about 3 months, until placenta develops.
Hormones secreted by corpus luteum during this period maintain the pregnancy. Abortion occurs if corpus luteum becomes
inactive or removed before third month of pregnancy, i.e. before placenta starts secreting the hormones.
During each menstrual cycle, along with ovarian changes, uterine changes also occur simultaneously .
Uterine changes occur in three phases:
1. Menstrual phase
2. Proliferative phase
3. Secretory phase.
Menstrual phase -After ovulation, if pregnancy does not occur, the thickened endometrium is
shed or desquamated. This desquamated endometrium is expelled out through vagina along
with blood and tissue fluid. The process of shedding and exit of uterine lining along with blood
and fluid is called menstruation or menstrual bleeding. It lasts for about 4 to 5 days. This
period is called menstrual phase or menstrual period.
Proliferative phase -It extends usually from 5th to 14th day of menstruation, i.e. between the
day when menstruation stops and the day of ovulation. It corresponds to the follicular phase of
ovarian cycle. At the end of menstrual phase, only a thin layer of endometrium remains, as most
of the endometrial stroma is desquamated.
SECRETORY PHASE--It extends between 15th and 28th day of the menstrual cycle, i.e.
between the day of ovulation and the day when menstruation of next cycle commences. After
ovulation, corpus luteum is developed in the ovary. It secretes a large quantity of progesterone
along with a small amount of estrogen. Estrogen causes further proliferation of cells in uterus,
so that the endometrium becomes more thick. Progesterone causes further enlargement of
endometrial stroma and further growth of glands.
• HORMONES INVOLVED IN REGULATION
• The regulatory system functions through the hormones of hypothalamo-
pituitary-ovarian axis.
1. Hypothalamic hormone: GnRH
2. Anterior pituitary hormones: FSH and LH
3. Ovarian hormones: Estrogen and progesterone.
• Follicular Phase
The release of GnRH stimulates the secretion of FSH and LH from anterior pituitary. LH
induces the synthesis of androgens from theca cells of growing follicle FSH promotes
aromatase activity in granulosa cells of the follicle, resulting in the conversion of androgens
into estrogen. It also promotes follicular development Estrogen is responsible for
development and growth of Graafian follicle. It also stimulates the secretory activities of
theca cells Estrogen also exerts a double feedback control on GnRH
Initially, when estrogen secretion is moderate, it exerts a negative feedback control on GnRH so that
GnRH secretion is inhibited. This leads to decrease in secretion of FSH and LH . During later period of
follicular phase, when a large amount of estrogen is secreted by the maturing follicle, it exerts a positive
feedback effect on GnRH secretion. Now, GnRH secretion is increased, resulting in secretion of large
quantity of FSH and LH. This in turn, facilitates the growth of Graafian follicle, In addition, estrogen
shows the following actions:
i.Increases the number of FSH and LH receptors on the granulosa cells of follicles and increases the
sensitivity of these cells for FSH and LH
ii. Facilitates the faster growth of Graafian follicle
LH is necessary to provide the final touches for the growth of Graafian follicle. It stimulates the secretion
of estrogen. At the same time, it stimulates the theca cells to secrete progesterone.
• Luteinizing hormone:
1.Induces development of corpus luteum from the follicle (devoid of ovum) by converting the
granulosa cells into lutein cells
2. Stimulates corpus luteum to secrete progesterone and estrogen
3. Necessary for the maintenance of corpus luteum.
 Role of FSH also plays a role during luteal phase.
 Follicle-stimulating hormone:
 Maintains the secretory activity of corpus luteum
Stimulates lutein cells to secrete inhibin, which inturn inhibits FSH secretion. If the ovum is not fertilized or if implantation of
ovum does not take place, the changes in the level of the hormones produce some effects on corpus luteum which are:
1. Progesterone and estrogen secreted from corpus luteum, inhibit the secretion of FSH and LH from anterior pituitary by negative
feedback
2. Granulosa lutein cells secrete another hormone called inhibin which is also secreted by Sertoli cells of testes in males: Inhibin
also inhibits the secretion of FSH and LH by negative feedback.
3. In the absence of FSH and LH, the corpus luteum becomes inactive
4. Finally, the corpus luteum regresses by means of luteolysis; so progesterone and estrogen are not available
5. Absence of progesterone and estrogen induces the secretion of GnRH from hypothalamus
6. GnRH stimulates the secretion of FSH and LH from anterior pituitary
7. FSH and LH stimulate the new immature follicles, resulting in the commencement of next cycle.
APPLIED PHYSIOLOGY –
 Amenorrhea: Absence of menstruation Hypomenorrhea: Decreased menstrual bleeding.
 Menorrhagia: Excess menstrual bleeding Oligomenorrhea: Decreased frequency of menstrual bleeding.
 Polymenorrhea: Increased frequency of menstruation Dysmenorrhea: Menstruation with pain.
 Metrorrhagia: Uterine bleeding in between menstruations.