The document summarizes the key aspects of the human menstrual cycle. It describes that the menstrual cycle typically lasts 28 days and involves changes in the ovaries, uterus, vagina and cervix. The cycle consists of three phases - the menstrual phase (days 1-5) where the uterine lining sheds, the proliferative phase (days 6-14) where the lining thickens in response to estrogen, and the secretory phase (days 15-28) where the lining prepares for potential embryo implantation under the influence of progesterone. If implantation does not occur, progesterone and estrogen levels fall, causing the uterine lining to detach and bleed out as menstruation.

1. MENSTRUAL CYCLE
KIRAN INAM
MS-HCM
BS RENAL DIALYSIS TECHNOLOGY

3. INTRODUCTION
Menstrual cycle is defined as cyclic events that take
place in a rhythmic fashion during the reproductive
periods of a women’s life.
Menstrual cycle start at the age of 12 to 15 years.
The commencement of menstrual cycle is called
menarche.
Menstrual cycle ceases at the age of 45 to 50 years.
Permenant cessation of menstrual cycle in old age is
called menopause.

4. DURATION OF MENSTRUAL CYCLE
Duration of menstrual cycle is usually 28 days. But
under physiological conditions it may vary between
20 and 40 days.

5. CHANGES DURING MENSTRUAL
CYCLE
During each menstrual cycle series of changes occur
in ovary and accessory organs.
The changes are divided into four groups.
1. Ovarian changes
2. Uterine changes
3. Vaginal changes
4. Cervical changes

6. PHASES OF MENSTRUAL CYCLE
Menstrual phase (days 1-5)
Proliferative/ Preovulatory phase (Days 6-14)
Secretory/ Postovulatory phase (Days 15-28)

8. MENSTRAL PHASE (DAYS 1-5)
In this menstruation phase, the uterus sheds all but
the deepest part of its endometrium.
The thick hormone dependent functional layer of the
endometrium detaches from the uterine wall, a
process that is accompanied by bleeding for 3-5
days.
The detached tissue and blood pass out through the
vagina as the menstrual flow.
At the beginning of this stage ovarian hormones are
at their lowest normal levels and FSH levels begin to
rise.

9. PROLIFERATIVE PHASE (DAYS 6-14)
Under the influence of rising blood levels of
estrogens, the basal layer of endometrium generates
a new functional layer.
Once again the endometrium becomes velvety, thick
and well vascularized.
Normally cervical mucus is thick and sticky, but rising
estrogen levels cause it to thin and become
crystalline, forming channels that facilitate the
passage of sperm into the uterus.

10. PROLIFERATIVE PHASE (DAYS 6-14)
Ovulation which takes <5 minutes, occurs in the
ovary at the end of the proliferative stage in response
to sudden release of LH.
LH also converts the ruptured follicle to a corpus
luteum.

11. SECRETORY PHASE (DAYS 15-28)
During the secretory phase the endometrium
prepares for implantation of an embryo.
Rising levels of progesterone from corpus luteum act
on the estrogen primed endometrium, causing the
arteries to elaborate.
The uterine glands enlarge, coil and begin secreting
nutrients glycogen in to the uterine cavity, these
nutrients sustain the embryo until it has implanted in
the blood rich endometrium lining.

12. SECRETORY PHASE (DAYS 15-28)
If fertilization has not occurred, the corpus luteum
begins to degenerate toward the end of secretory
phase, as LH level decline.
Progesterone levels fall, depriving the endometrium
of hormonal support, and endometrial cells die,
setting the stage for menstruation to begin on day 28.