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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.