The menstrual cycle involves changes in the ovaries and uterus driven by hormones. It begins at menarche and typically repeats every 21-35 days until menopause. Each cycle can be divided into the follicular phase, ovulation, and luteal phase. During the follicular phase, FSH stimulates follicle growth and estrogen production. Ovulation occurs when an LH surge causes an egg to be released. In the luteal phase, the corpus luteum produces progesterone to thicken the uterine lining if implantation occurs. If not, progesterone levels drop and menstruation begins, restarting the cycle.

1. Menstrual Cycle
- By- Shabana Godme

2. Introduction
• The first period usually begins between twelve and fifteen years of
age, a point in time known as menarche.
• The typical length of time between the first day of one period and
the first day of the next is 21 to 45 days in young women and 21 to 35
days in adults (an average of 28 days). Menstruation stops occurring
after menopause which usually occurs between 45 and 55 years of
age. Bleeding usually lasts around 3 to 7 days.
• The menstrual cycle is governed by hormonal changes. These changes
can be altered by using hormonal birth control to prevent pregnancy.

3. • Each cycle can be divided into three
phases based on events in the ovary
(ovarian cycle) or in the uterus (uterine
cycle).
• The Ovarian Cycle consists of the
• the Uterine Cycle is divided into
follicular
phase
ovulation
luteal
phase
menstruation
proliferative
phase
secretory
phase

4. The Cycle-
Menstruation
• The menstrual cycle starts with the menstrual phase, when menstrual
flow occurs and it lasts for 3-5 days.
• The average blood loss during menstruation is 35 milliliters with 10–
80 ml considered normal.
• It results due to the breakdown of endometrial lining o the uterus and
its blood vessels which forms liquid that comes out through vagina.
• The flow of menses normally serves as a sign that a woman has not
become pregnant. (However, this cannot be taken as certainty, as a
number of factors can cause bleeding during pregnancy).
• On Day 1 of the menstrual cycle, estrogen and progesterone levels are
low. Low levels of estrogen and progesterone signal the pituitary
gland to produce Follicle Stimulating Hormone (FSH). FSH begins the
process of maturing a follicle (fluid-filled sac in the ovary containing
an egg).

5. You may have period symptoms like these:
• cramps
• tender breasts
• bloating
• mood swings
• irritability
• headaches
• tiredness
• low back pain

6. Follicular phase
At birth
• The process of formation of a mature female gamete is called Oogenesis.
• It is initiated during the embryonic development stage when a couple of
million gamete mother cells ( oogonia) are formed within each fetal ovary; no
more oogonia are formed and added after birth.
• These cells start division and enter Prophase 1 of the meiotic division and get
temporarily arrested at that stage, called primary oocytes.
• Each primary oocyte then gets surrounded by a layer of granulosa cells and
then called the primary follicle.
• A large number of these follicles degenerate during the phase from birth to
puberty and at puberty only 60,000 - 80,000 primary follicles are left in each
ovary.

7. At puberty
• The primary follicles get surrounded by more layers of granulosa cells and a new theca and
called secondary follicles.
• The secondary follicle soon transforms into tertiary follicle which is characterised by a fluid
filled cavity called antrum. The theca layer is organised into an inner theca interna and an
outer theca externa.
At this stage, the primary oocyte within the tertiary follicle grows in size and completes its
first meiotic division. It is an unequal division resulting in the formation of a large haploid
secondary oocyte and a tiny first polar body.
• The tertiary follicle further changes into the mature
follicle or Graafian follicle.
• The secondary oocyte forms a new membrane
called Zona Pellucida surrounding it.

8. • It starts when the hypothalamus sends a signal to your pituitary gland to release
follicle-stimulating hormone (FSH). This hormone stimulates your ovaries to
produce around 5 to 20 small sacs called follicles. Each follicle contains an
immature egg.
• Only the healthiest egg will eventually mature. (On rare occasions, a woman may
have two eggs mature.) The rest of the follicles will be reabsorbed into your body.
• The maturing follicle sets off a surge in estrogen that thickens the lining of your
uterus. This creates a nutrient-rich environment for an embryo to grow.
• The average follicular phase lasts for about 16 days. It can range from 11 to 27
days, depending on your cycle.

9. Proliferative Phase
• The changes in the ovary and the
uterus are induced by changes in
the levels of pituitary (FSH, LH) and
ovarian hormones (estrogen,
progesterone).
• The uterine lining is regenerated in
preparation for receiving a fertilised
egg (should fertilisation occur). The
regrowth of the lining each month
is needed to create an environment
suitable for development of a
fertilised egg.

10. • Both LH and FSH attain a peak level.
• The spiral arteries elongate.

11. Ovulation
• Rapid secretion of LH leads to its maximum level
during the mid-cycle called the LH surge induces
rupture of the Graafian follicle and thereby releasing
the ovum into the fallopian tubes, where the egg
begins its winding journey towards the uterus.
• Usually only 1 egg is released in this ovulation
proccess. Rarely a woman will develop and release
two or more eggs, and this is when multiple
pregnancy occurs (e.g. triplets, depending on the
number of eggs released).
• ovulation usually occurs 14 days before the
beginning of the next menstrual period.
• An ovum lives for 12-24 hours.
• 6 days to getting pregnant.

12. Luteal Phase
• The luteal phase is the final phase of
the ovarian cycle and it corresponds to
the secretory phase of the uterine
cycle. During the luteal phase, the
pituitary hormones FSH and LH cause
the remaining part of the Graafian
follicle to transform into Corpus
Luteum.
• The Corpus Luteum secretes large
amounts of progesterone which is
essential for maintenance of the
endometrium.
• Such an endometrium is necessary for
implantation of the fertilized ovum and
other events of pregnancy.
• The luteal phase lasts for 11 to 17 days.
The average length is 14 days.

13. Secretory Phase
• During the secretory phase, the corpus luteum produces progesterone, which
plays a vital role in making the endometrium receptive to implantation of the
blastocyst and supportive of the early pregnancy, by increasing blood flow
and uterine secretions and reducing the contractility of the smooth muscle in
the uterus; it also has the side effect of raising the woman's basal body
temperature.
• Estrogen and Progesterone are at at their peak level during the secretory
phase, and they prepare the endometrium to secrete the nutrients necessary
to nourish a conceptus if a fertilized egg were to implant in it.

16. If the egg isn't fertilized
• The Corpus Luteum degenerates and forms Corpus Albicans.
• If conception and implantation do not occur, the pituitary gland will
reduce LH and FSH production. Without the presence of LH, the
corpus luteum deteriorates and, subsequently, the estrogen and
progesterone levels drop rapidly. The drop in estrogen and
progesterone levels then triggers the endometrium to shed, causing
menstruation to begin and allowing the cycle to start over again at
the menstrual phase.

17. If the egg gets Fertilized
• Once released from the ovaries an egg may be fertilised by male
sperm, in which case it will be nourished by the uterine lining and
establish a pregnancy. Pregnancy changes the woman’s hormonal
balance and interrupts the menstrual and ovarian cycles.
• Upon fertilization Corpus Luteum continues to secreate progesterone.
• Progesterone inhibits maturation of any other follicle in ovaries and
ovulation.
• your body will produce human chorionic gonadotropin (hCG). This is
the hormone pregnancy tests detect. It helps maintain the corpus
luteum and keeps the uterine lining thick.