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THE MENSTRUAL CYCLE
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DR. UTOO, B. TERKIMBI
(MB, BCh; FWACS, FMCOG)
Lecturer/Consultant Obstetrician &
Gynaecological SurgeonObstetrics/Gynaecology DepartmentCHS,BSU /BSUTH, MAKURDI.
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OUTLINE
Introduction
Embryology
Ovarian cycleEndometrial cycle
Mechanism of menstrualbleeding
Menstrual symptoms
Conclusion14/10/2014UTOO BT2
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INTRODUCTION
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.
Menstruation- It is the visible
manifestation of cyclical physiological
uterine bleeding due to shedding of theendometrium.
This follows invisible interplay ofhormones mainly through the
hypothalamo-pituitary-ovarian axis.
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Introduction cont.
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Menarche-11-15 years; mean=13years.
The period extending from the
beginning of a period to the beginning of
the next one is called menstrual cycle.
Menstrual cycles occur between
menarche and menopause.
Mean age of menopause is 51 years.
Cycle length-21 to 35 days, mean=28
days.
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Introduction cont.
The cycle is usually irregular just aftermenarche and one or two years before
menopause.
Duration of menstruation- 2 to 7 days. Amount of blood loss20 to 80 mls
AV.=35mls.
Menstrual discharge consist of; Darkaltered blood, mucus, vaginal epithelial
cells, fragments of endometrium, PGs,
enzymes and bacteria. 14/10/2014UTOO BT5
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Introduction cont.
The length of the menstrual cycle variesconsiderably among women and does not
remain constant in the same individual.
Emotional disturbances such as fear, chronic
debilitating disease, abrupt changes in climate
and other environmental factors could cause
menstrual irregularity.
Menstrual cycle is divided into two phases
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EMBRYOLOGY
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Germ Cells Migrates from endoderm of the york sac in the
region of the hindgut into the genital ridge.Telopheron directs this migration which is by
amoeboid activity or chemotactic mechanism. The germ cells undergo rapid mitotic division and
by 20 weeks the number reaches 7 million.
Some enter the prophase of the first meiotic
division and are called primary oocytes They become surrounded by flat cells from
stroma
( primordial follicles).
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Embryology cont.
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Primary oocytes are arrested in the diplotene stage ofprophase of first meiotic division, until ovulation.
Prophase; Leptotene,Zygotene,Pachytene andDiplotene).
At 20 weeks intrauterine life7million oocytes.
At birth- 2million.
At puberty-400,000.
Only 400 ovulates during entire reproductive period.
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Morphology of the oocyte
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Ovarian Cycle
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Development/maturation of a follicle
Ovulation
Formation of corpus luteum/degeneration.
The entire process last for about 4 weeks.
Recruitment (pre antral phase)
Takes 85 days and spread over 3 ovarian cycles
About 20 antral follicles(5-10/0vary) devevelop in
each cycle. This is controlled by FSH.
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Ovarian cycle cont.
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Selection of a dominant follicle and its maturation
DF appear 5-7 days of the cycle.
Its selection is determine by high E2, lowandrogen: E2
ratio, maximum FSH receptors.
The FSH induces LH receptors on the granulosacells of DF. This leads to LH surge in mid cyclewith consequent ovulation, luteinisation andsecretion of P4.
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Selection & maturation of
DF
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Ovarian cycle cont.
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Ovulation The mature follicle which measures 20mm, just
prior to ovulation reaches the surface of theovary.
The cumulus detached from the wall so that theovum floats. This eventually escape through astigma near the surface of the ovary.
This is made possible by LH surge, FSH rise
plasminogen activator plasminogenplasmin help lysis of the wall of the follicle.
A secondary oocyte in 2nd meiotic divisionarrested at metaphase is released.
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A mature graafian follicle
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Hormonal interplay in
normal ovulatory cycle
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Ovarian cycle cont.
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Corpus luteum formation/degeneration
Proliferation(immediate)
Vascularization(24 hours)
Maturation(7-8days) Regression(22-23 days)
If pregnancy occurs, between 23-28 days
hyperplasia occur due to chorionic gonadotropin .
The growth peaks at 8thweek. Regression occursdue to low levels of hCG most frequently at 6
months.
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Endometrial Cycle
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The endometrium is the lining epithelium of theuterine cavity above the level of the internal
cervical os.
It consist of surface epithelium, glands, stromal
and blood vessels.
Two distinct divisions exist-This are; basalzone(stratum basalis), superficial functional zone.
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Endometrial cycle cont.
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The functional zone is under the influence offluctuating cyclic ovarian hormones, E2 and P4.
The changes in the endometrium during ovulatory
cycles are divided into 4 phases.
These are;
Regenerative phase
Proliferative phase
Secretory phase
Menstruation.
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Mechanism of menstrual
bleeding
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Degenerative changes vascular in origin
Stasis of blood and spasm of arterioles
Leakage of blood through damaged vessels
Auto digestion of functional zone by proteolyticenzymes
Blood and superficial layer shed into uterinecavity
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Mechanism cont.
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Blood coagulates but soon liquefies by plasmin
Menstrual flow stops as a result of myometrialcontraction, vasoconstriction, local aggregation of
platelets, fibrin deposition
PGF2(particularly), PGE2and PGI2play variouscrucial roles.
Peptides e.g-inhibin, activin and follistatin andIGF modulate the action of FSH as well as LH.
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Menstrual symptoms
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Vaginal bleeding
Lower abdominal pains
Dysmenorrhea( incapacitating pains)
Pelvic discomfort, backache Fullness of breast or mastalgia
Headache, depression
PMS!!!!
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An ovular menstruation
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Follicular growth without selection of DF
Rising E2
GnRH suppression anovulation
Endometrium remains proliferative or hyperplastic
The fall of E2results in synchronous shedding ofendometrium and heavy menstruation.
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CONCLUSION
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Menstruation is the end result of interplay of
hormones through the Hypothalamo-pituitary-
ovarian axis and local PGs leading to
endometrial shedding through a patent outflowtract.
It is a physiological process of cyclical changesinvolving the ovaries, endometrium, cervix,
vaginal and other parts of the body in general.
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