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Female reproductive Female reproductive physiologyphysiology

Tianjin Medical University General HospitalTianjin Medical University General Hospital

Obstetrics and Gynecology DepartmentObstetrics and Gynecology Department

Bai XiaohongBai Xiaohong

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Fetal period Neonatal period Childhood Adolescence(puberty) Sexual maturity (Child –bearing period) menstrual cycle pregnancy Perimenopause Senility

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Puberty menopause Child –bearing period

menstruation pregnancy

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After birth, the gonads are quiescent until they are activated by gonadotropins from pituitary to bring about the final maturation of the reproductive system.

This period of final maturation is known as puberty.

Puberty is the period when the endocrine and gametogenic function of the gonads first develop to the point where reproduction is possible.

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Menopause : The human ovary gradually becomes unresponsive to gonadotropins with advancing age , and its function decline, so that sexual cycles and menstruation disappear.

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Menstrual cycle: The reproductive system of adult women shows regualr cyclic changes .

Periodic preparation for fertilization and pregnancy.

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Menstrual cycleMenstrual cycle Hypothalamic-Pituitary Axis Hypothalamic-Pituitary Axis Ovarian Cycle Ovarian Cycle Histophysiology of the Endometrium Histophysiology of the Endometrium Spermatogenesis, Sperm, CapacitationSpermatogenesis, Sperm, Capacitation and Fertilizationand Fertilization Cleavage, Morula, BlastocystCleavage, Morula, Blastocyst

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PURPOSE & REQUIREMENTPURPOSE & REQUIREMENT

1.1. MasterMaster the follicle development and the follicle development and

steroid hormone secretory patternssteroid hormone secretory patterns

2.2. KnowKnow cyclic changes in the ovary and cyclic changes in the ovary and

endometriumendometrium

3.3. KnowKnow the regulation of the menstrual the regulation of the menstrual

cyclecycle

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menses

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Normal pattern of menses

1. 75% menstrual blood is of arterial ,only 25% is of venous origin.

2. It contains tissue debris, prostaglandins,and fibrinolysins.

3. Mean interval is 28 days +/- 7 days.

4. Mean duration is 3~5 days (1~8 days).

5. Average blood loss with menstruation is 35-50 ml. More than 80 ml is abnormal.

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Each menstrual cycle represents a complex Each menstrual cycle represents a complex interaction between the interaction between the hypothalamus, hypothalamus, pituitary gland, ovaries pituitary gland, ovaries and and endometrium.endometrium.

Cyclic changes in Cyclic changes in gonadotropingonadotropin and and steroid steroid hormoneshormones induce functional as well as induce functional as well as morphologic in the ovary, resulting in morphologic in the ovary, resulting in follicular maturation,ovulation, and corpus follicular maturation,ovulation, and corpus luteum formation.luteum formation.

Similar changes at the level of the Similar changes at the level of the endometriumendometrium allow for successful allow for successful implantation of the development embryo.implantation of the development embryo.

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HypothalamusHypothalamus

PituitaryPituitary

OvaryOvary endometriumendometrium

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Hypothalamic- Pituitary AxisHypothalamic- Pituitary Axis

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The The pituitary glandpituitary gland lies below the lies below the

hypothalamus at the base of the brain within hypothalamus at the base of the brain within

a bony cavity and is separated from the a bony cavity and is separated from the

cranial cavity by a condensation of dura cranial cavity by a condensation of dura

mater overlying the sella turcica.mater overlying the sella turcica.

The pituitary gland is divided into two The pituitary gland is divided into two

portions:portions:neurohypophysisneurohypophysis and and

adenohypophysisadenohypophysis

Pituitary glandPituitary gland

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Pituitary HormonesPituitary Hormones Ovarian secretion depends on the action Ovarian secretion depends on the action

of hormones secreted by the anterior of hormones secreted by the anterior pituitary. pituitary.

The anterior pituitary contains different The anterior pituitary contains different cell types that produce 6 established cell types that produce 6 established protein hormones: protein hormones: FSH, LHFSH, LH, TSH, , TSH, prolactin,prolactin, GH, ACTH. GH, ACTH.

The gonadotropins, The gonadotropins, FSH and LH,FSH and LH, are are synthesized and stored in cells in anterior synthesized and stored in cells in anterior pituitary, called gonadotrophspituitary, called gonadotrophs

FSH:FSH: follicle-stimulating hormone follicle-stimulating hormone LH:LH: luteinizing hormone luteinizing hormone

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Pituitary hormones

FSHFSH LHLH TSHTSH ProlactinProlactin GHGH ACTHACTH

gonadotropins

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FSH ,LH, and TSH are glycoproteins, FSH ,LH, and TSH are glycoproteins, consisting of consisting of and and subunits. subunits.

The The subunits of FSH, LH,and TSH are subunits of FSH, LH,and TSH are identical. The same identical. The same subunits is also subunits is also present in human chorionic present in human chorionic gonadotropin(hCG).gonadotropin(hCG).

The The subunits are individual for each subunits are individual for each hormone.hormone.

Gonadotropins

Ganodotropin secretory Ganodotropin secretory patternpattern

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Follicular phaseFollicular phase begins with the begins with the onset of menses onset of menses and culminates in and culminates in the preovulatory the preovulatory surge of LH.surge of LH.

Luteal phaseLuteal phase begins with the begins with the onset of the onset of the preovulatory surge preovulatory surge of LH and ends of LH and ends with the first day of with the first day of menses.menses.

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Decreasing levels of estradiol and progesteroneDecreasing levels of estradiol and progesterone from the regressing corpus luteum of the from the regressing corpus luteum of the preceding cycle preceding cycle initiate a rise of FSHinitiate a rise of FSH by a by a negative feedback mechanismnegative feedback mechanism, which stimulates , which stimulates follicular growth and estradiol secretion. follicular growth and estradiol secretion.

Negative feedback

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At At lower levels of estradiollower levels of estradiol there is a there is a negative negative effecteffect on the ready-release form of LH from the on the ready-release form of LH from the pool of Gonadotropins in the pituitary pool of Gonadotropins in the pituitary gonadotrophs.gonadotrophs. As estradiol levels rise later in the follicular As estradiol levels rise later in the follicular phase, there is a phase, there is a positive feedbackpositive feedback on the on the release of storage gonadotropins, resulting in release of storage gonadotropins, resulting in the LH surge and ovulation.the LH surge and ovulation.

negative effect

positive feedback

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positive feedback

negative effect

negative effect

During the luteal phase, both LH and FSH During the luteal phase, both LH and FSH are significantly are significantly suppressedsuppressed through the through the negative feedbacknegative feedback effect of elevated effect of elevated circulating estradiol and progesterone circulating estradiol and progesterone levels.levels.

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positive feedback

negative effect

negative effect

This inhibition persists until progesterone and This inhibition persists until progesterone and estradiol level decline near the end of the luteal estradiol level decline near the end of the luteal phase as a result of corpus luteal regression, phase as a result of corpus luteal regression, should pregnancy fail to occur.should pregnancy fail to occur.The net effect is a rise in serum FSH, which The net effect is a rise in serum FSH, which initiates follicular growth for the next cycle.initiates follicular growth for the next cycle.The duration of the corpus luteum’s functional The duration of the corpus luteum’s functional regression is such that menstruation generally regression is such that menstruation generally occurs 14days after the LH surge in the absence of occurs 14days after the LH surge in the absence of pregnancy.pregnancy.

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prolactin Prolactin is secreted by lactotrophs. Serum prolactin levels do not change

strikingly during the normal menstrual cycle.

Prolactin may participate in control of ovarian steroidgenesis.

The physiologic role of prolactin during the normal menstrual cycle has not been established.

Hyperprolactinemia may alter gonadotropin secretion.

HypothalamusHypothalamus

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The secretion of the anterior pituitary The secretion of the anterior pituitary hormones is regulated by the hypothalamic hormones is regulated by the hypothalamic hypophysiotropic hormones.hypophysiotropic hormones.

Five peptides or biogenic amines that affect Five peptides or biogenic amines that affect the reproductive cycle have been isolated the reproductive cycle have been isolated from the hypothalamus: from the hypothalamus:

GnRHGnRH gonadotropin-releasing hormonegonadotropin-releasing hormone

PIFPIF prolactin release-inhibiting factorprolactin release-inhibiting factor

TRH TRH thyrotropin-releasing hormonethyrotropin-releasing hormone

SRIF SRIF somatotropin release-inhibiting factorsomatotropin release-inhibiting factor

CRFCRF corticotropin-releasing factorcorticotropin-releasing factor

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GnRH(gonadotropin-releasing hormone)gonadotropin-releasing hormone)

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GnRH is a decapeptide that is synthesized GnRH is a decapeptide that is synthesized primarily in the primarily in the arcuate nucleusarcuate nucleus. It is . It is responsible for the synthesis and release of responsible for the synthesis and release of both LH and FSHboth LH and FSH..

It usually causes the release of more LH It usually causes the release of more LH than FSH, it is commonly called LH-releasing than FSH, it is commonly called LH-releasing hormone(LH-RH) or LH- releasing hormone(LH-RH) or LH- releasing factor(LRF) factor(LRF)

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Both FSH and LH appear to be present in two different forms within the pituitary gonadotrophs--releasable form and storage form.

GnRH reaches the anterior pituitary via the hypophyseal portal vessels and stimulates the synthesis of both FSH and LH, which are stored within gonadotrophs.

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Subsequently, GnRH activates and transforms these molecules into releasable forms.

GnRH can also induce immediate release of both LH and FSH into the circulation.

GnRH may have a direct effect on ovarian function as well.

GnRH is secreted in a pulsatile fashion GnRH is secreted in a pulsatile fashion throughout the menstrual cycle.throughout the menstrual cycle.

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Several mechanisms control the Several mechanisms control the secretion of GnRHsecretion of GnRH

EstradiolEstradiol appears to appears to enhance enhance hypothalamic release of GnRH and may hypothalamic release of GnRH and may help induce the midcycle LH surge by help induce the midcycle LH surge by increasing GnRH release or by enhancing increasing GnRH release or by enhancing pituitary responsiveness to the GnRH.pituitary responsiveness to the GnRH.

GonadotropinsGonadotropins have an have an inhibitory effectinhibitory effect on GnRH release.on GnRH release.

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The hypothalamus produces PIF, which exerts chronic inhibition of prolactin release from the lactotrophs.

A number of pharmacologic agents that affect dopaminergic mechanism influence prolactin release. Dopamine itself inhibits prolactin release directly within the adenohypophysis. Based on these observations, it has been proposed that hypothalamic dopamine may be the major PIF.

PIF

Ovarian cycleOvarian cycle

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Steroid hormoneSteroid hormone

estrogens estrogens

progestinsprogestins

androgensandrogens

Follicle development Follicle development

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EstrogensEstrogens

During early follicular development, During early follicular development, circulating estradiol levels are circulating estradiol levels are relatively relatively lowlow..

About 1 week before ovulation, levels About 1 week before ovulation, levels begin begin to increaseto increase, at first slowly, then , at first slowly, then rapidly. The levels generally rapidly. The levels generally reach a reach a maximummaximum 1 day before ovulation. 1 day before ovulation.

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EstrogensEstrogens After this peak and before ovulation, there After this peak and before ovulation, there

is a marked and precipitous fall.is a marked and precipitous fall. During the luteal phase, estradiol rises to During the luteal phase, estradiol rises to

a maximum 5 to 7 days after ovulation and a maximum 5 to 7 days after ovulation and returns to baseline shortly before returns to baseline shortly before menstruation.menstruation.

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EstrogensEstrogens

The naturally occuring estrogens are 17The naturally occuring estrogens are 17ββ--estradiol, estrone, and estriol.estradiol, estrone, and estriol.

They are secreted primarily by the They are secreted primarily by the granulosa and the thecal cells of the granulosa and the thecal cells of the ovarian follicle,the corpus luteum,and the ovarian follicle,the corpus luteum,and the placenta. placenta.

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Effects on female genitalia Ovary :facilitate the growth of the

ovarian follicles Uterine:increase blood flow increase muscle amount myometrium more active endometrium proliferation tubes : increase the motility cervix: mucus thinner and more

alkaline Vaginal :epithelium becomes

cornfied

Estrogens

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Cervix mucus

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ProgestinsProgestins

During follicular development, the ovary During follicular development, the ovary secrets only very small amounts of secrets only very small amounts of progesterone and 17-hydroxyprogesterone.progesterone and 17-hydroxyprogesterone.

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ProgestinsProgestins Just before ovulation, the unruptured but Just before ovulation, the unruptured but

luteinzing graafian follicle begins to luteinzing graafian follicle begins to produce increasing amounts of produce increasing amounts of progesterone.progesterone.

At about this time, a marked increase also At about this time, a marked increase also occurs in serum 17-hydroxyprogesterone.occurs in serum 17-hydroxyprogesterone.

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As with estradiol, secretion of progestins As with estradiol, secretion of progestins by the corpus leteum reaches a maximum by the corpus leteum reaches a maximum 5 to 7 days after ovulation and returns to 5 to 7 days after ovulation and returns to baseline shortly before menstruation.baseline shortly before menstruation.

ProgestinsProgestins

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ProgestinsProgestins The elevation of basal body temperature The elevation of basal body temperature

(BBT)is temporally related to the central (BBT)is temporally related to the central effect of progesteroneeffect of progesterone..

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Should pregnancy occur, progesterone Should pregnancy occur, progesterone levels, and therefore basal body levels, and therefore basal body temperature, remain elevated.temperature, remain elevated.

ProgestinsProgestins

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Effects on female genitalia Uterine:inhibit uterine

contraction,

endometrium secretory cervix: mucus thick ,

tenacious.

Vaginal :secreted thick mucus ,epithelium proliferates

Progestins

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AndrogensAndrogens Both the ovary and the adrenal glands Both the ovary and the adrenal glands

secrete small amounts of testosterone, secrete small amounts of testosterone, but most of the testosterone is derived but most of the testosterone is derived from the metabolism of androstenedione, from the metabolism of androstenedione, which is also secreted by both the ovary which is also secreted by both the ovary and the adrenal gland.and the adrenal gland.

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AndrogensAndrogens Near midcycle, an increase occurs in Near midcycle, an increase occurs in

plasma androstenedione, which reflect plasma androstenedione, which reflect enhanced secretion from the follicle.enhanced secretion from the follicle.

During the luteal phase, a second rise During the luteal phase, a second rise occurs in androstenedione, which reflects occurs in androstenedione, which reflects enhanced secretion by the corpus luteum.enhanced secretion by the corpus luteum.

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Follicular development

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Primordial follicles undergo sequential development, differentiation, Primordial follicles undergo sequential development, differentiation, and maturation until a mature graafian follicle is produced. The follicle and maturation until a mature graafian follicle is produced. The follicle then ruptures, releasing the ovum. Subsequent luteinization of the then ruptures, releasing the ovum. Subsequent luteinization of the ruptured follicle produces the corpus luteum.ruptured follicle produces the corpus luteum.

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Primordial folliclePrimordial follicle At approximately 8 to 10 At approximately 8 to 10

weeks of fetal development, weeks of fetal development, oocytes become oocytes become progressively surrounded progressively surrounded by precursor granulosa by precursor granulosa cells , which then separate cells , which then separate themselves from the themselves from the underlying stroma and underlying stroma and oocyte by a basal lamina.oocyte by a basal lamina.

Primordial follicle

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Primary folliclePrimary follicle at between 20 and 24 at between 20 and 24

weeks’s gestationweeks’s gestation in response to in response to

gonadotropin and ovarian gonadotropin and ovarian steroidsteroid

the follicular cells become the follicular cells become cuboidal and the stromal cuboidal and the stromal cells around the follicle cells around the follicle become prominent. become prominent.

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Secondary follicleSecondary follicle

As granulosa cells As granulosa cells proliferate, a clear proliferate, a clear gelatinous material gelatinous material surrounds the ovum, surrounds the ovum, forming the zona forming the zona pellucida.pellucida.

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the innermost three or the innermost three or four layers of rapidly four layers of rapidly multiplying granulosa multiplying granulosa cells become cuboidal cells become cuboidal and adherent to the ovum and adherent to the ovum (cumulus oophorus)(cumulus oophorus)

a fluid-filled antrum forms a fluid-filled antrum forms among the granulosa cellamong the granulosa cell

primary oocyte migrates primary oocyte migrates eccentrically to the wall of eccentrically to the wall of the folliclethe follicle

Graafian follicleGraafian follicle

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The granulosa cells of the The granulosa cells of the

cumulus,which are in close cumulus,which are in close

contact with the pellucida contact with the pellucida

become elongated and form become elongated and form

the corona radiatathe corona radiata

Covering the granulosa cells is Covering the granulosa cells is

a thin membrane:the theca a thin membrane:the theca

interna and the theca externa.interna and the theca externa.

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During each cycle, a cohort of follicles is During each cycle, a cohort of follicles is recruited for development. Among the recruited for development. Among the many developing follicle, only one usually many developing follicle, only one usually continues differentiation and maturation continues differentiation and maturation into a follicle that ovulates.into a follicle that ovulates.

The remaining follicles undergo atresia.The remaining follicles undergo atresia.

?

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Follicular maturation is dependent on the local Follicular maturation is dependent on the local development of development of receptors for FSH and LH.receptors for FSH and LH.

FSH-R are present on granulosa cellsFSH-R are present on granulosa cells.. Under Under FSH stimulationFSH stimulation, granulosa cells , granulosa cells

proliferate and the number of FSH receptor proliferate and the number of FSH receptor increases.increases.

Estrogens, particularly Estrogens, particularly estradiol, enhanceestradiol, enhance the the induction of FSH receptors and act induction of FSH receptors and act synergistically with FSH to increase LH synergistically with FSH to increase LH receptors.receptors.

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During early stages of folliculogenesis, LH receptors are present only on the theca interna layer.

FSH also enhances the induction of LH receptors on the granulosa cells of the follicle that is destined to ovulate.

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The presence of greater numbers of FSH-R and granulosa cells and increased induction of aromatase enzyme and its receptors may differentiate between the follicle of the initial cohort that will develop normally and those that will undergo atresia.

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Growth factors such as insulin, insulin-like growth factor(IGF), fibroblast growth factor(FGF), and epidermal growth factor(EGF) may also play significant mitogenic roles in folliculogenesis , including enhanced responsiveness to FSH.

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ovulationovulation The ovulation occurs 36 to 44 hours The ovulation occurs 36 to 44 hours

after onset of the preovulatory surge after onset of the preovulatory surge of LH.of LH.

Follicle

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ovulationovulation

The preovulatory LH surge initiates a The preovulatory LH surge initiates a sequence of structural biochemical sequence of structural biochemical changes that culminate in ovulation.changes that culminate in ovulation.

Before ovulation, a general Before ovulation, a general dissolution of the entire follicular dissolution of the entire follicular wall occurs, particularly the portion wall occurs, particularly the portion that is on the surface of the ovary.that is on the surface of the ovary.

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With degeneration of the cells on the With degeneration of the cells on the surface, stigma forms, and the follicular surface, stigma forms, and the follicular basement membrane finally bulges basement membrane finally bulges through the stigma.through the stigma.

When this ruptures, the oocyte and corona When this ruptures, the oocyte and corona radiata are expelled into the peritoneal radiata are expelled into the peritoneal cavity, and ovulation takes place.cavity, and ovulation takes place.

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ovulationovulation

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Human oocyte-corona-cumulus complexHuman oocyte-corona-cumulus complex

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Ovulation is a gradual phenomenon, with the collapse of the follicle taking from several minutes to as long as an hour or more.

The oocyte adheres to the surface of the ovary, allowing an extended period during which the muscular contractions of the tube may bring it in contact with the tubal epithelium.

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Luteinization and corpus luteumLuteinization and corpus luteum After ovulation and under the influence of After ovulation and under the influence of

LH, the granulosa cells of the ruptured LH, the granulosa cells of the ruptured follicle undergo luteinization.follicle undergo luteinization.

Corpus lutuem: the luteinized granulosa the luteinized granulosa cells, plus the surrounding theca cells, cells, plus the surrounding theca cells, capillaries, and connective tissue.capillaries, and connective tissue.

Corpus lutuem produces copious amounts Corpus lutuem produces copious amounts of progesterone and some estradiol.of progesterone and some estradiol.

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The normal functional life span of the The normal functional life span of the corpus luteum is about 14 days.corpus luteum is about 14 days.

After this time it regresses, and unless After this time it regresses, and unless pregnancy occurs, menstruation ensues pregnancy occurs, menstruation ensues and the corpus luteum is gradually replace and the corpus luteum is gradually replace by corpus albicans.by corpus albicans.

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Histophysiology of the Histophysiology of the EndometriumEndometrium

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EndometriumEndometrium

The endometrium is uniquely The endometrium is uniquely responsive to the circulating responsive to the circulating estrogens , progestins.estrogens , progestins.

It is this responsiveness that gives It is this responsiveness that gives rise to menstruation and makes rise to menstruation and makes implantation and pregnancy implantation and pregnancy possible.possible.

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The endometrium is divided into two The endometrium is divided into two zones:zones:

FunctionalisFunctionalis : undergoes cyclic : undergoes cyclic changes in morphology and function changes in morphology and function during the menstrual cycle and is during the menstrual cycle and is sloughed off at menstruation .sloughed off at menstruation .

BasalisBasalis : relatively unchange during : relatively unchange during each menstrual cycle and after each menstrual cycle and after menstruation provides stem cells for menstruation provides stem cells for the renewal of the functionalis.the renewal of the functionalis.

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Cyclic changes in histophysiologyCyclic changes in histophysiology

Menstrual phaseMenstrual phase Proliferative phaseProliferative phase Secretory phaseSecretory phase

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Menstrual phaseMenstrual phase The first Day of menstruation is taken as The first Day of menstruation is taken as

day 1 of the menstrual cycle.day 1 of the menstrual cycle. The first 4 days of cycle are defined as The first 4 days of cycle are defined as

the menstrual phase.the menstrual phase. During this phase, there is disruption and During this phase, there is disruption and

disintegration of the endometrial glands disintegration of the endometrial glands and stroma, leukocyte infiltration, and red and stroma, leukocyte infiltration, and red blood cell extravasation.blood cell extravasation.

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Despite these degenerative changes, early Despite these degenerative changes, early evidence of renewed tissue growth is evidence of renewed tissue growth is usually present at this time within the usually present at this time within the basalis of the endometrium.basalis of the endometrium.

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Proliferative phaseProliferative phase

The proliferative phase is The proliferative phase is characterized by endometrial characterized by endometrial proliferation or growth secondary to proliferation or growth secondary to estrogenic stimulation.estrogenic stimulation.

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The bases of the endomatrial glands lie deep within the basalis, these epithelial cells are not destroyed during menstruation.

As menstruation ends each month, they provide and migrate through the stroma to form a new epithelial lining of the endometrium and new endometrial glands.

Proliferative phaseProliferative phase

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During this phase of the cycle, the large During this phase of the cycle, the large increase in estrogen secretion causes increase in estrogen secretion causes marked cellular proliferation of the marked cellular proliferation of the epithelial lining, the endometrial glands, epithelial lining, the endometrial glands, and the connective tissue of the stroma. and the connective tissue of the stroma.

The endometrium increasea in The endometrium increasea in thickness,the glands are drawn out. .thickness,the glands are drawn out. .

Numerous mitoses are present in these Numerous mitoses are present in these tissues.tissues.

There is an increase in the length of the There is an increase in the length of the spiral arteries, which traverse almost the spiral arteries, which traverse almost the entire thickness of the endometrium. entire thickness of the endometrium.

Proliferative phaseProliferative phase

Endometrium of

proliferative phase

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Proliferative phaseProliferative phase By the end of this phase, cellular By the end of this phase, cellular

proliferation and endometrial growth have proliferation and endometrial growth have reached a maximum, the spiral arteries are reached a maximum, the spiral arteries are elongated and convoluted, and the elongated and convoluted, and the endometrial glands are straight, with endometrial glands are straight, with narrow lumens containing some glycogen.narrow lumens containing some glycogen.

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Secretory phaseSecretory phase Following ovulation, progesterone Following ovulation, progesterone

secretion by the corpus luteum stimulates secretion by the corpus luteum stimulates the glandular cells to secrete glycogen, the glandular cells to secrete glycogen, mucus, and other substances. The glands mucus, and other substances. The glands become tortuous and the lumens are become tortuous and the lumens are dilated and filled with these substances.dilated and filled with these substances.

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The stroma becomes edematous. Mitoses are rare. The spiral arteries continue to extend into

the superficial layer of endometrium and become convoluted.

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Secretory phaseSecretory phase By day 23, the corpus lutuem begins to By day 23, the corpus lutuem begins to

regress, secretion of progesterone and regress, secretion of progesterone and estradiol declines, and the endometrium estradiol declines, and the endometrium undergoes involution.undergoes involution.

About 1 day prior to the onset of About 1 day prior to the onset of menstruation, marked constriction of the menstruation, marked constriction of the spiral arterioles takes place, causing spiral arterioles takes place, causing ischemia of the endometrium followed by ischemia of the endometrium followed by leukocyte infiltration and red blood cell leukocyte infiltration and red blood cell extravasation.extravasation.

The resulting necrosis causes menstruation The resulting necrosis causes menstruation or sloughing of the endometrium.or sloughing of the endometrium.

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Spermatogenesis, sperm Spermatogenesis, sperm capacitation, and fertilizationcapacitation, and fertilization

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Fertilization normally takes place in the Fertilization normally takes place in the fallopian tube.fallopian tube.

Fertilization or conception is the union of Fertilization or conception is the union of male and female pronuclear elements. male and female pronuclear elements.

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Spermatogenesis requires about 74 days. Spermatogenesis requires about 74 days. Together with transportation, a total of Together with transportation, a total of about 3 months elapses before sperm are about 3 months elapses before sperm are ejaculated.ejaculated.

The sperm achieve motility during their The sperm achieve motility during their passage through the epididymis.passage through the epididymis.

Sperm capacitation occurs,which renders Sperm capacitation occurs,which renders them capable of fertilization in vivo, when them capable of fertilization in vivo, when they removed from the seminal plasma they removed from the seminal plasma after ejaculation.after ejaculation.

sperm

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The average ejaculate contains 2 to 8 ml of The average ejaculate contains 2 to 8 ml of semensemen

40 to 300 million sperm may be deposited in 40 to 300 million sperm may be deposited in vaginavagina

more than 50% of which are move forwardmore than 50% of which are move forward

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More than 15% of which should be morphologically normal. More than 15% of which should be morphologically normal.

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Fewer than 200 sperm achieve proximity Fewer than 200 sperm achieve proximity to the egg. Only one sperm fertilizes a to the egg. Only one sperm fertilizes a single egg released at ovulation. single egg released at ovulation.

Capacitation is the physiologic change Capacitation is the physiologic change that sperm must undergo in the female that sperm must undergo in the female reproductive tract before fertilization. reproductive tract before fertilization.

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sperm

oocyte

The The acrosomeacrosome, a modified lysosome, lies over the , a modified lysosome, lies over the sperm head as a kind of “chemical drill-bit” sperm head as a kind of “chemical drill-bit” designed to enable the sperm to burrow its way designed to enable the sperm to burrow its way into the oocyte.into the oocyte.

The The acrosome reactionacrosome reaction is one of the principal is one of the principal components of capacitationcomponents of capacitation

coronaFirst PB

ovumzona

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The overlying plasma membrane becomes unstable and eventually breaks down, releasing Hyaluronidase corona-dispersing enzyme.

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After traversing the zona, the postacrosomal region of the sperm head fuses with the oocytes membrane, and the sperm nucleus is incorporated into the ooplasm.

This process triggers the cortical reaction that results in changes in the oocyte membrane and zona . The cortical reaction prevent the entrance of further sperm into oocyte.

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Following penetration of the Following penetration of the oocyte, the sperm nucleus oocyte, the sperm nucleus decondenses to form the male decondenses to form the male pronucleus, which approaches pronucleus, which approaches and finally fuses with the female and finally fuses with the female pronucleus at syngamy to form pronucleus at syngamy to form the zygote.the zygote.

Fertilization restores the diploid Fertilization restores the diploid number of chromosomes and number of chromosomes and determines the sex of the determines the sex of the zygote.zygote.

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Intracytoplasmic sperm injection (ICSI)

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Cleavage, morula, blastocystCleavage, morula, blastocyst

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4-cell 8-cell

blastocyst

Implanted blastocyst

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THANKS FOR YOUR ATTENDANCETHANKS FOR YOUR ATTENDANCE