Menstrual Cycle

NORMAL MENSTRUAL CYCLE mean duration of the MC Mean 28 days (only 15% of ) Range 21-35

average duration of menses 3-8 days

normal estimated blood loss Approximately 30 ml

ovulation occur Usually day 14 36 hrs after the onset of mid-cycle LH surge

NORMAL MENSTRUAL CYCLE the phases of the MC & ovulation regulates by: Interaction between hypothalamus, pituitary & ovaries

mean age of menarche & menopause are: Menarche 12.7 Menopause 51.4

The CycleStrongly linked to the endocrine system (hormone based and paracrine based)Typically takes 28 days to cycle through 4 phasesFollicularOvulationLutealMenstruationHormones raise and fall

Ovulation

FollicularBegins when estrogen levels are lowAnterior pituitary secretes FSH and LH, stimulation follicle to developCells around egg enlarge, releasing estrogenThis causes this uterine lining to thicken

OvulationLH and FSH still being released, for another 3-4 daysFollicle ruptures, releasing ova into the Fallopian tubes

LutealNow empty follicle changes to a yellow colour, becomes corpus luteumContinues to secrete estrogen, but now beings to release progesteroneProgesterone further develops uterine liningIf pregnant, embryo will release hormones to preserve corpus luteum

MenstruationMenstruationIf no embryo, the corpus luteum begins to disintegrateProgesterone levels drop, uterine lining detaches, menstruation can beginTissue, blood, unfertilized egg all dischargedCan take from 3-7 days

*prof. aj

prof. aj

PHYSIOLOGYOF THE MENSTRUAL CYCLE Ovulation divides the MC into two phases:

1-FOLLICULAR PHASE -Begins with menses on day 1 of the menstrual cycle & ends with ovulation

FOLLICULAR PHASEMATURATION OF THE FOLLICLE (FOLLICULOGENESIS)

FSH primordial follicle Primary follicle Secondary follicle tertiary or antral follicle

OVULATION The dominant follicle protrudes from the ovarian cortex Gentle release of the oocyteMechanism of follicular rupture 1- Follicular pressure2-Enzymatic rupture of the follicular wall

ENDOMETRIAL CHANGES DURING THE MENSTRUAL CYCLE1-Basal layer of the endometrium -Adjacent to the myometrium -Unresponsive to hormonal stimulation -Remains intact throughout the menstrual cycle

2-Functional layer of the endometrium

MENSTRUATIONPeriodic desquamation of the endometriumJust before menses the endometrium is infiltrated with leucocytesProstaglandins are maximal in the endometrium just before menses Prostaglandins constriction of the spiral arterioles ischemia & desquamation Followed by arteriolar relaxation, bleeding & tissue breakdown

HYPOTHALAMIC ROLE IN THE MENSTRUAL CYCLEThe hypothalamus secretes GnRHGnRH activity is first evident at pubertyRelease of GnRH is modulated by ve feedback by: steroids gonadotropins

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