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Female Reproductive Physiology

Dr.Mohammed Sharique Ahmed QuadriAssistant professor physiology

Al Maarefa College

بسم الله الرحمن الرحيم

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Objectives • Describe oogenesis and the stages of follicle development through

ovulation and the formation of a corpus luteum.• Explain the hormonal interactions involved in the control of

ovulation. • Describe the changes in the secretion of ovarian sex steroids during a

nonfertile cycle and explain the function and fate of the corpus luteum.

• Explain how the secretion of FSH and LH is controlled through negative and positive feedback mechanisms during a menstrual cycle.

• Describe the cyclic changes that occur in the endometrium and the hormonal mechanisms that cause these changes.

• Graphically illustrate the timing of changes in blood levels of FSH, LH, estradiol, progesterone, and correlate these with structural changes in the endometrium and the ovary seen during the menstrual cycle.

Female Reproductive Physiology

• Characterized by complex cycling

• Ovaries– Primary female reproductive organs

• Produce ova (oogenesis)• Secrete female sex hormones

– Estrogen – progesterone

Female Sex Hormones–These are steroid hormone –Estrogen

» Maturation and maintenance of entire female reproductive system .

» Essential for ova maturation and release

» Establishment of female secondary sexual characteristics

» Essential for transport of sperm from vagina to fertilization site in oviduct

» Contributes to breast development in anticipation of lactation

– In general action of estrogen is important in preconception events

Female Sex Hormones

–Progesterone » Important in preparing suitable environment for

nourishing a developing embryo/fetus» Contributes to breasts’ ability to produce milk

– In general progesterone is important in post conception events

OOGENESIS [GAMETOGENENSIS]

• Formation of Primary oocytes from oogonium is completed before birth – 7 million. Soon Atresia starts and the number starts reducing.

• After birth the number is reduced to 2 million. At puberty – 300, 000.During reproductive age only 400 mature and ovulate .

• The first meiotic division of primary oocyte begins during embryonic life but is arrested at prophase and is completed only at ovulation [Release of ovum from ovary].

• At ovulation it forms Secondary Oocyte which contains half the Chromosomes (22+x) and 1st polar body which undergoes degeneration.

• The secondary oocyte then undergoes the 2nd meiotic division but is arrested at metaphase, and completed during fertilization.

• It form the mature ovum (22+x) and the 2nd polar body.

• The second polar body too undergoes degeneration

Oogenesis

Oogenesis • Identical steps of

chromosome replication and division during gamete production in both sexes– Timing and end result are

very different

Spermatogenesis Oogenesis

Accomplished within two months

Take anywhere from 12 to 50 years to complete on cyclic basis from onset of puberty until menopause

Postpubertal male can produce several hundred million sperm each day

Female born with limited, largely nonrenewable supply of germ cells

Each primary spermatocyte yields four equally viable spermatozoa

Each primary oocyte yields only one cytoplasm-rich ovum and three cytoplasm-poor polar bodies that disintegrate

Ovarian Cycle

• Average ovarian cycle lasts 28 days• Normally interrupted only by pregnancy• Finally terminated by menopause• Consists of two alternating phases

– Follicular phase(1-14 days )• Dominated by presence of maturing follicles

– Luteal phase(15-28 days)• Characterized by presence of corpus luteum

Ovarian Cycle-Follicular phase– Granulosa cells of some primary follicles

proliferate

– Theca cells proliferate (estrogen secreting cells)

– Under the effect of FSH some of the follicles grows rapidly forming secondary or antral follicle capable of secreting estrogen

– Oocyte inside each follicle enlarges

Ovarian Cycle-Follicular phase

– One follicle usually grows more rapidly and mature (graafian follicle) about 14 days after onset of follicular development

– Graafian follicle bulges on ovarian surface -ruptures to release oocyte from ovary (ovulation)- facilitated by burst in LH secretion

– Released oocyte enters oviduct where it may or may not be fertilized

Development of the Follicle, Ovulation, and Formation and Degeneration of the Corpus Luteum

Ovarian Cycle-Luteal phase

• Last 14 days of ovarian cycle

– The remnants of the ruptured graafian follicle develop into Corpus luteum under influence of LH (leuteinization)

– The granulosa cells are filled with yellowish lipid- lutein.

– Becomes highly vascularized

Ovarian Cycle-Luteal phase

– Corpus Luteum has endocrine functions and it secretes progesterone & estrogen (more of progesterone). It remains for 14 days.

– If fertilization does not occurs it degenerates into Corpus Albicans.

– If fertilization takes place it persists until placenta is formed & secrete increase quantity of progesterone & estrogen (corpus luteum of pregnancy)

Ovarian Cycle

Regulation of Ovarian Cycle by hormonal interactions

1. During follicular phase, rise in FSH signals ovarian follicle to secrete more estrogen

2.Rise in estrogen feeds back to inhibit FHS secretion which declines as follicular phase proceeds

3.LH rises in follicular phase• As it peaks in mid-cycle, it triggers ovulation

4.Estrogen output decreases and mature follicle is converted to a corpus luteum

5.Corpus luteum secretes progesterone and estrogen during luteal phase

– Progesterone output inhibits release of FSH and LH• Low LH – corpus luteum degenerates• Progesterone levels decline

6.FSH can start to rise again, initiating new cycle

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Production of estrogen by ovarian follicle

Correlation Between

Hormonal Levels and

Cyclic Ovarian and Uterine

Changes

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Feedback control of FSH & LH during follicular phase

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Feedback control of FSH & LH during ovulation

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Feedback control of FSH & LH during luteal phase

Uterine Cycle

• Menstrual cycle• Reflects hormonal changes during ovarian cycle• Averages 28 days• Outward manifestation of cyclic changes in uterus

is menstrual bleeding once during each cycle• Consists of three phases

– Menstrual phase (1-5days)– Proliferative phase (6-14 days)– Secretory or progestational phase (15-28 days)

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• Estrogen stimulates growth of both endometrium and myometrium .

• It also induces synthesis of progesterone receptors in endometrium.

• Progesterone: make endometrial connective tissue loose and edematous

• Growth of endometrial blood vessels and glands to secrete glycogen

Uterine Cycle-Menstrual phase

– 1-5 days of cycle – Characterized by discharge of blood and

endometrial debris from vagina– First day of menstruation is considered start

of new cycle– Coincides with end of ovarian luteal phase

and onset of follicular phase

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Uterine Cycle-Menstrual phase – As corpus luteum degenerates the level of

progesterone & estrogen drops that results in -Release of uterine prostaglandin • Causes vasoconstriction of endometrial vessels

– Disrupts blood supply– Causes death of endometrium

• Stimulates mild rhythmic contractions of uterine myometrium

– Help expel blood and endometrial debris from uterine cavity out through vagina (menstrual flow)

• Bleeding lasts for 5-7 days 30-150 ml of blood is lost per cycle. Fibrinolysins are present which dissolves any clots.

Uterine Cycle• Proliferative phase (6-14days)

– Begins concurrent with last portion of ovarian follicular phase

• Endometrium starts to repair itself and proliferate under influence of estrogen from newly growing follicles

• Glands and arteries proliferate and there is increases thickness of endometrium

– Estrogen-dominant proliferative phase lasts from end of menstruation to ovulation

– Peak estrogen levels trigger LH surge responsible for ovulation

Uterine CycleSecretory or progestational phase(15-28day)

– Uterus enters this phase after ovulation when new corpus luteum is formed

– Corpus luteum secretes large amounts of progesterone and estrogen

• Under effect of Progesterone– The endometrium grows further in thickness with

increase in secretions of glands and arteries become more coiled

– The secretion are rich in electrolytes, enzymes and glycogen which provide nourishment to the developing embryo before implantation, if fertilization has taken place.

– If fertilization and implantation do not occur• Corpus luteum degenerates• New follicular phase and menstrual phase begin once again

Various factors can disrupt the menstrual cycle

• Weight loss/low body weight

• Disordered eating

• Vigorous physical activity

• Stress

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References

• Human physiology by Lauralee Sherwood, seventh edition

• Text book physiology by Guyton &Hall,11th edition

• Text book of physiology by Linda .s contanzo,third edition