The Female Reproductive Cycle

8/7/2019 The Female Reproductive Cycle

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Ovarian and Uterine Cycles

Objective

Inform the audience about the female reproductive

cycle

The Female Reproductive Cycle


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Overview

y Occurs in the menarche stage of puberty

y Average age 12 years old

y Cessation of menstrual cycle occurs during menopause

(average age 52)y 4 stages of menstruation


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Hormones

y Major player in the menstrual cycle

y Estrogen

y Promotes the development and maintenance of female

reproductive structures (especially the endometrial lining of theuterus)

y Assists in the control of fluid and electrolyte balance within the

body.

y Prepares the follicle for the release of an egg.

Estrogen also has many other functions.


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Progesterone:

y Secreted at ovulation

y Helps to prepare the endometrium (womb lining) for the

implantation of an egg

yPrepares mammary galnds for milk production

y Primarily concerned with the procreation and survival of the

fetus.


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FSH Follicle StimulatingHormone

y Stimulates the follicles

y a follicle is a balloon shaped structure which is filled with fluid

and contains an egg, follicles are found in the ovaries)

y

Ripens several eggsy At the same time the ovaries release oestrogen.


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LHLutenising hormone:

y Further develops the follicles

y Triggers ovualtion and stimulates production of other

hormones necessary for the post ovulatory stage of the

menstrual cycle.y The secretion of hormones is a complex affair.Various parts

of the body become involved in a myriad of chemical

transactions.


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6 phases of menstruation

Name of phaseAverage start day

assuming a 28-day cycleAverage end day

menstrual phase

(menstruation)1 4

Preovulatory phase 5 13

ovulatory phase (ovulation) 13 16

Postovulatory phase 16 28

http://en.wikipedia.org/wiki/Menstrual_cycle


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Menstrual phasey Day 1 to 4

y Events in the ovaries:

y FSH causes several primordial follicles to develop into primaryand secondary follicles

y Follicles can take months to develop

y Events in the uterus

y Menstrual flow 50-150mL of blood, tissue fluid, mucus, andepithelial cells

yOccurs due to declining levels of progesterone and estrogensstimulate release of prostaglandins that cause uterine spiralarterioles to constrict

y Flow passes from the uterine cavity though cervix and vaginainto external environment


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Preovulatory phasey Day 5 to 13

y Variable in length accounts for most differences in cyclelength

y Events in the ovaries:

y Some secondary follicles in ovaries begin to secrete estrogensand inhibins

y Estrogens and inhibins secreted by the dominant follicledecrease secretion ofFSH.y

Causes other less developed follicles to stop growingy Fun fact non-identical twins or triplets result when two or

three secondary follicles become co dominant and are ovulatedand fertilised at same time

http://www.youtube.com/watch?v=8_rfZ_qj1z4&f

eature=related


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Preovulatory phase cont.y Normally, the one dominant secondary follicle becomes the mature

follicley Continues to enlarge until it is more than 20mm in diameter and ready for

ovulation

y Forms blisterlike bulge due to the swelling antrum on surface of ovary

y During final maturation follicle continues to increase production of estrogens

y Events in the uterus

y Estrogens in blood stimulate repair of the endometrium

y Cells of the stratum basalis undergo mitosis and produce a new stratumfunctionalis

y As endometrium thickens, the short, straight endometrial glandsdevelop, and the arterioles coil and lengthen as they penetrate thestratum functionalis

y Thickness of the endometrium approximately doubles to about 4-10mm


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Postovulatory phasey Day 16-28

y Most constant part of reproductive cycle

y Mature follicle collapses

y

Basement membrane between granulosa cells and thecainterna breaks down

y Blood clot forms from mminor bleeding of ruptured follicle

y Follicle becomes corpus hemorrhagicum

y Hemo = blood

y Rrhagic = bursting forth

y LH influences theca interna cells to mix with granulosa cells

y Transforms into corpus luteum cells


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Postovulatory phase cont.y Futher events depend on fertilization or non fertilization:

y Non fertilisation

y corpus luteum has a life span of only 14 days

y Then its secretory activity declines, degenerates to corpus albicans

y As this occurs rise of GnRH, LH and FSH occurs due to the loss ofnegative feedback suppression by ovarian hormones. Folliculargrowth resumes and a new cycle begins

y Fertilisation

y corpus luteum lives beyond two weeks

y Human Chorionic Gonadotropin (hCG) prevents its degenerationy hCG is produced by the chorion of the embryo about 8 days after

fertilization

y hCG is the indicator in pregnancy tests


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Postovulatory phase cont.y Events in the Uterus

y progesterone and estrogens produced by the corpus luteum promote growth

and coiling of the endometrial glands

y Vascularisation of the superficial endometrium and thickening of the

endometrum


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Documents

The Female Reproductive Cycle