Menstrual cycle
Lecture 2
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Objectives
• To list the phases of the menstrual cycle
• To describe the hormonal changes during
each phase
• To describe the hormonal changes behind
ovulation
• To point the source and control of the
hormones involved in the menstrual cycle
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What is a menstrual cycle?
• The menstrual cycle is the series of changes a
woman's body goes through to prepare for a
pregnancy.
• About once a month, the uterus grows a new
lining (endometrium) to get ready for a
fertilized egg.
• When there is no fertilized egg to start a
pregnancy, the uterus sheds its lining.
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What is a menstrual cycle?
• This is the monthly menstrual bleeding (also
called menstrual period) that women have
from their early teen years until menopause,
around age 50.
• The menstrual cycle is from Day 1 of bleeding
to Day 1 of the next time of bleeding.
Although the average cycle is 28 days, it is
normal to have a cycle that is shorter or
longer.
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NORMAL MENSTRUAL CYCLE
What is the mean duration of the MC?
Mean 28 days (only 15% of ♀)
Range 21-36
What is the average duration of menses?
3-7days
What is the normal estimated blood loss?
Approximately 20 – 80 ml
When does ovulation occur?
Usually day 14
10 -- 12 hrs after the onset of mid-cycle LH surge.
How many have women menstrual cycle with life time?
300—400
How many oocyte at birth female has?
2 million
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What controls the menstrual cycle?
• Hypothalamus and pituitary gland send hormone
signals back and forth with your ovaries. These
signals get the ovaries and uterus ready for a
pregnancy.
• The hormones estrogen and progesterone play
the biggest roles in how the uterus changes
during each cycle.
• Estrogen builds up the lining of the uterus.
• Progesterone increases after an ovary releases an
egg (ovulation)
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Symptoms of painful periods
1.
2.
3.
4.
5.
6.
Pains in the abdomen
Pain in the vagina
Feeling nauseous and generally unwell
Diarrhoea
Sweating
Fatigue
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Related Terms
• Oligomenorrhoea : Irregular, infrequent periods
• Menarche: is the age of the first menstrual cycle
and culminates at the age of Puberty.
• Dysmenorrhea - painful menstruation
– Possible cause - prostaglandins
• Amenorrhea - absence of menstruation
– Primary amenorrhea - when girl has not.
• Mittelschmerz - middle pain; cramping in lower
abdomen that occurs during ovulation.
• Menopause is cessation of regular menstrual cycle.
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Factors effect of menarche starts
1.
2.
3.
4.
5.
Genetics
Geographical location.
Nutrition
Weight
Psychological factors
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Menstrual Cycle Consists of:
1. Ovarian Cycle
2. Endometrial Cycle
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The Phases of the Menstrual Cycle
The overian cycle has 4 phases:
1. Follicular phase - proliferative phase or
Pre ovulatory phase
2. Ovulation
3. Luteal phase - secretory phase or postovulatory phase
4. Menstruation
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The Phases of the ovarian Cycle
1. Follicular phase :
•
high levels of FSH secreted
– Function is to stimulate follicles in the ovaries
One follicle begins to mature and brings an egg
to maturity 1- 14day
– Follicle secretes estrogen
– Increase level of estrogen secreted by maturating follicle that
effect on the endometrial proliferation.
2. Ovulation phase
• Follicle ruptures open and releases the mature egg 14 day promoted by
LH surge
• Decrease level of estrogen
• Life span of ovum is 24 hrs.
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The Phases of the Menstrual Cycle
3. Luteal phase
after releasing an egg, the follicle turns into the corpus
luteum15 -28day
• The corpus luteum secrets progesterone to Prepare
endometruim for implantation and to secret glycogen and
mucus.
• The absence of fertilization the corpus luteum begins to
degenerate that will lead Estrogen and Progesterone
decrease.
4. Menstruation - shedding of the inner lining of the
uterus 28 day.
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Endometrial cycle
1.Proliferative phase
• Start in day 5
• Start endometrial proliferates in response of estrogen
• Increase thickness dramatically from 0.5 – 5mm.
• Cervical mucus becomes thin and clear and more
alkaline
2. Secretory phase :
• begins at ovulation
• progesterone secreted by the corpus luteum stimulates
the glands of the endometrium to start secreting the
nourishing substances preparation of implantation.
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Endometrial cycle
3. Ischemic phase
• If fertilization does not occur, the ischemic phase
begins.
• Estrogens and progesterone level drop
• Corpus luteum degenerate.
• Spasm of arterioles and lead of shedding of the
endometrium.
4. menstrual phase :
• Rupture of spiral arteries
• The beginning of menstrual flow marks the end of one
menstrual cycle
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Changes in the Uterus:
Stage 1- Day 1-5
menstruation
Stage 2 Day 5- 13 preovulatory stage
Stage 4 Day 15-28 postovulatory stage
Stage 3 Day 14
Ovulation
Ovarian Hormones
Days 1-14
Pituitary
Gland
Produces
FSH
Follicle Stimulating Hormone
Triggers formation of the
Follicle
Within the ovary
Produces
Estrogen & Ovum
Triggers uterine lining thickening
Days 14 - 28
Pituitary
Gland
Produces
LH
Lutinizing Hormone
Triggers Ovulation
and the formation of the
Corpus Lutium
Within the ovary
Produces
Progesterone
Continues uterine lining thickening
Fluctuations in Mood
• Premenstrual syndrome - PMS
• PMS is a combination of severe physical
and psychological symptoms, such as depression
and irritability, occurring just before
menstruation
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Fluctuations in Performance
• Research on intellectual or athletic
performance generally shows no fluctuations
over the cycle
• Research on academic performance,
problem solving, memory, or creative
thinking shows no fluctuations over the
cycle
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What Causes the Fluctuations in Mood
• Biological factors
– Fluctuations in levels of hormones
• Environmental factors
– Menstrual taboos and cultural expectations
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What is Menopause?
• 12 months of amenorrhea (no menses)
• Average age 51
• Derived from the Greek words “men” (month) and
“pausis” (cessation)
• Primary ovarian function stops
• Marks the permanent end of fertility
Menopausal Symptoms
•
•
•
•
•
•
•
•
•
Hot flashes
Sleep disturbances
Vaginal dryness
Mood changes
Difficulty concentrating
Memory impairment
Bladder irritability/urgency
Changes in balance
Decreased interest in sex, possibly decreased response to
sexual stimulation
Other Causes to Consider
•
•
•
•
•
Thyroid disorders
Pheochromocytoma
Leukemia
Cancer
Infection
References
• http://www.ux1.eiu.edu/~cfjcd/Menstrual_Cy
cle.
• http://members.optushome.com.au/medstuff
/Menstrual%20cycle.pdf
• http://www.drugs.com/cg/menstruation.html
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