Menstrual & Ovulatory Cycle

7/27/2019 Menstrual & Ovulatory Cycle

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Female Reproductive organs

Primary female

reproductive organsare ovaries whileaccessory are theducts like uterine

tubes, uterus, andvagina


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The Ovaries


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The Ovaries

The ovaries on the outer sideare surrounded by a layer ofepithelial cells called the

germinal epithelium. Embedded in their cortex are

ovarian follicles in variousstages of development.

The remains of rupturedfollicle after ovulation is calledcorpus luteum


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Uterine Tubes

Uterine tubes receive the

ovulated oocyte and provide

a site for fertilization. They

empty into the uterus. They expand distally around

the ovary forming the

ampulla which ends in the

funnel-shaped, ciliatedinfundibulum containing

fingerlike projections called

fimbriae.


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Uterine Tubes

The uterine tubes have nocontact with the ovaries andthe ovulated oocyte is

cast into the peritonealcavity. Beating cilia on thefimbriae create currents tocarry the oocyte into theuterine tube.

The oocyte is carriedtoward the uterus byperistalsis and ciliary actionof the lining ciliaryepithelium of the tube.


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Uterus

The uterus is a hollow,thick-walled organlocated in the pelvisanterior to the rectum andposterio superior to the

urinary bladder. Its partsare

Fundus rounded regionsuperior to the entrance ofthe uterine tubes

Body major portion ofthe uterus

Isthmus narrowedregion between the bodyand cervix


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Uterus

Cervix narrow neck whichprojects into the vaginainferiorly

Cervical canal

cavity ofthe cervix thatcommunicates with: The vagina via the external os

The uterine body via theinternal os

Cervical glands secretemucus that covers theexternal os and blockssperm entry except duringmidcycle


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Ovarian Cycle

Monthly series of events occurring

in ovaries associated with the

maturation of an egg is called an

ovarian cycle. It consists offollicularphase and luteal phase

Follicular phase period offollicle growth (days 114). During it

primordial follicle becomes primary,secondary and tertiary follicles and

follicular cells become granulosa

cells secreting estrogen.


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Ovarian Cycle

Follicular phase cont. The fullsized follicle (vesicular follicle)

bulges from the external surface ofthe ovary. The primary oocyte

completes meiosis I, and the stage

is set for ovulation.

Ovulationoccurs at the mid of thecycle and a twinge of pain is

sometimes felt in pelvis at ovulation

called Mittelschmerz


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Ovarian Cycle

Luteal phase A period ofcorpus luteum activity (days 14

28). After ovulation, the rupturedfollicle collapses, granulosa cells

enlarge, and along with internal

thecal cells, form the corpus

luteum The corpus luteum

secretes progesterone and

estrogen..


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Ovarian Cycle

Luteal phasecont.

If pregnancy does not occur, the

corpus luteum degenerates in 10

days, leaving a scar (corpus

albicans) in the ovary. If

pregnancy occurs, the corpus

luteum produces hormones until

the placenta takes over that role(at about 3 months of gestation)


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MENSTRUAL CYCLE

What actuallyhappens in

those 28 days?


14/27The ovarian and menstrual cycle of the human female


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Uterine (Endometrial) Cycle

Monthly cyclical changes in the

endometrium of uterus for prepration

of implantation (in the event of

fertilization) and for menstruation (in

the absence of fertilization) is calleduterine cycle.

The uterine endometrial cycle can be

divided into three phases:

the proliferative phase,

the secretary,

the menstrual phase.


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Proliferative Phase

The proliferative or follicular, phase,spans from the end of themenstruation until ovulation.

Under the influence of increasinglevels of estrogen secreted byovarian follicles all elements ofendometrium proliferate.

The raw surface of endometrium is

again covered with epitheliumwhich proliferates out from theremains of the stems of uterineglands. The stromal cells increase


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Proliferative Phase cont.

Endometrial glands elongate with

cells containing some glycogen.But it is not secreted during the

follicular phase.

Spiral arteries supplying blood

also elongate. Stratum

functionalis thus resumed

again.


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Secretary Phase

The luteal, or secretory phase,

begins at ovulation and lasts until

the menstrual phase of the nextcycle.

At the beginning of the luteal

phase, progesterone induces the

endometrial glands to secreteglycogen, mucus, and other

substances. These glands become

tortuous and have large lumens

due to increased secretary activity.


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Secretary Phase cont.

The spiral arteries extend into the

superficial layer of the

endometrium.

In the absence of fertilization by

day 23 of the cycle, the corpus

luteum begins to degenerate and

consequently ovarian hormonelevels decrease.


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Uterine (Endometrial Cycle)


As estrogen and progesterone

levels decrease, the

endometrium undergoes

involution.

Days 25-26 of the menstrual

cycle, endothelin and thromboxin

begin to mediate

vasoconstriction of the spiral

arteries. The resulting ischemia

may cause some early menstrual

cramps.


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Uterine (Endometrial Cycle)


By day 28 of the

menstrual cycle, intense

vasoconstriction andsubsequent ischemia

cause mass apoptosis of

the stratum functionalis.


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Menstrual Phase

The menstrual phase begins as the

spiral arteries rupture secondary to

ischemia, releasing blood into the

uterus, and the apoptosed

endometrium is sloughed off. It

usually lasts four days. During this

period, the stratum functionalis is

completely shed.

Arterial and venous blood, remnants of

endometrial stroma and glands,

leukocytes, and red blood cells are all

present in the menstrual flow.


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Hormonal control

1. Pituitary gland release

Follicle Stimulating Hormone

(FSH) that acts on the ovary.

2. Ovarian follicles grow and

mature under influence of

FSH, and produce

increasing quantities of

estrogen

3. When levels of estrogenreach a threshold level, a

feed back process

decreases the production of

FSH by the pituitary.


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Hormonal control

4. Increased estrogen levels

trigger the release of

Luteinizing Hormone (LH) from

the pituitary gland

5. Ovulation occurs, that is

release of an egg from the

follicle.

6. The empty follicle forms the

corpus luteum, which produces

progesterone which maintains

the endometrium in a state of

readiness to receive a fertilized

egg


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Hormonal control

7. If the fertilized egg does

not implant itself the

progesterone level fallsand mensturation

commences.


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Summary of Reproductive

Hormones in Females

Hypothalamus releases Gonadotropin Releasing Hormone (GRH)

which binds with receptors in Ant. Pituitary

Anterior Pituitary releases Follicle Stimulating Hormone (FSH) and

Luteinizing Hormone(LH) pass in blood to site of action FSH acts on receptors in ovaries to stimulate development of the egg

follicles

LH causes rupture of egg follicles.

Rupture of egg triggers production ofestrogens and progestogens

from remaining tissues of follicle,corpus luteum

These hormones travel in blood to the brain

Hypothalamus senses levels, then may decrease release of GRH


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At end of this study you are able to

Describe structure of ovary, uterine tubesand uterus

Discuss the cyclic changes in the femalegenital tract, which include: The ovarian cycle (phases and hormonal

control). The uterine cycle (phases and hormonal

control)

Menstrual & Ovulatory Cycle

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