Chapter 28



Chapter 28The Reproductive SystemAn Introduction to the Reproductive SystemLearning Outcomes28-1List the basic structures of the human reproductive system, and summarize the functions of each.28-2Describe the structures of the male reproductive system and the roles played by the reproductive tract and accessory glands in producing spermatozoa; specify the composition of semen; and summarize the hormonal mechanisms that regulate male reproductive functions.An Introduction to the Reproductive SystemLearning Outcomes28-3 Describe the structures of the female reproductive system and the ovarian roles in oogenesis; explain the complete ovarian and uterine cycles; outline the histology, anatomy, and functions of the vagina; and summarize all aspects of the female reproductive cycle.28-4Discuss the physiology of sexual intercourse in males and females.An Introduction to the Reproductive SystemLearning Outcomes28-5Describe the reproductive system changes that occur with aging.28-6 Give examples of interactions between the reproductive system and each of the other organ systems.An Introduction to the Reproductive SystemThe Reproductive System Is the only system that is not essential to the life of the individualDoes affect other systemsThe male and female reproductive organs Produce and store specialized reproductive cells that combine to form new individualsReproductive organs Also secrete hormones that play major roles in the maintenance of normal sexual function28-1 Structures of the Reproductive SystemReproductive Structures Gonads are organs that produce gametes and hormonesDucts receive and transport gametesAccessory glands secrete fluids into ductsPerineal structures collectively known as external genitalia28-1 Structures of the Reproductive SystemThe Reproductive Tract Includes all chambers and passageways that connect ducts to the exterior of the bodyMale and Female Reproductive Systems Are functionally differentFemale produces one gamete per monthRetains and nurtures zygoteMale produces large quantities of gametesProduces 1/2 billion sperm per day28-1 Structures of the Reproductive SystemThe Male Reproductive System Testes or male gonadsSecrete male sex hormones (androgens)Produce male gametes (spermatozoa or sperm)28-1 Structures of the Reproductive SystemThe Female Reproductive System Ovaries or female gonadsRelease one immature gamete (oocyte) per monthProduce hormonesUterine tubes Carry oocytes to uterus – if sperm reaches oocyte, fertilization is initiated and oocyte matures into ovum UterusEncloses and supports developing embryo VaginaConnects uterus with exterior28-2 Male Reproductive FunctionsPathway of Spermatozoa TestisEpididymisDuctus deferens (vas deferens)Ejaculatory ductUrethra 28-2 Male Reproductive FunctionsAccessory Organs Secrete fluids into ejaculatory ducts and urethraSeminal glands (vesicles)Prostate glandBulbourethral glands28-2 Male Reproductive FunctionsExternal Genitalia Scrotum Encloses testesPenisErectile organContains distal portion of urethra28-2 Male Reproductive FunctionsThe TestesEgg shaped5 cm long, 3 cm wide, 2.5 cm thick (2 in. × 1.2 in. × 1 in.)Each weighs 10–15 g (0.35–0.53 oz)Hang in scrotum28-2 Male Reproductive FunctionsThe Scrotum Is a fleshy pouch Suspended inferior to perineumAnterior to anusPosterior to base of penis28-2 Male Reproductive FunctionsDescent of the TestesTestes form inside body cavity adjacent to kidneysGubernaculum testisIs a bundle of connective tissue fibersExtends from testis to pockets of peritoneumLocks testes in position (near anterior abdominal wall) as fetus grows28-2 Male Reproductive FunctionsDescent of the Testes During seventh monthFetus grows rapidlyCirculating hormonesStimulate contraction of gubernaculum testisEach testis:Moves through abdominal musculatureIs accompanied by pockets of peritoneal cavity28-2 Male Reproductive FunctionsAccessory Structures Accompany testis during descentForm body of spermatic cordDuctus deferensTesticular blood vessels, nerves, and lymphatic vessels28-2 Male Reproductive FunctionsThe Spermatic Cords Extend between abdominopelvic cavity and testesConsist of layers of fascia and muscleEnclose ductus deferens, blood vessels, nerves, and lymphatic vessels of testesPass through inguinal canalAre passageways through abdominal musculatureForm during development as testes descend into scrotumDescend into scrotum28-2 Male Reproductive FunctionsBlood Vessels of Testes Deferential arteryTesticular arteryPampiniform plexus of testicular veinNerves of TestesBranches of genitofemoral nerveFrom lumbar plexus28-2 Male Reproductive FunctionsMale Inguinal Hernias Are protrusions of visceral tissues into inguinal canalSpermatic cord (in closed inguinal canal)Causes weak point in abdominal wall Female Inguinal CanalsAre very smallContain ilioinguinal nerves and round ligaments of uterus28-2 Male Reproductive FunctionsThe Scrotum and the Position of the TestesIs divided into two chambers, or scrotal cavitiesEach testis lies in a separate scrotal chamberRapheIs a raised thickening in scrotal surfaceMarks partition of two scrotal chambers28-2 Male Reproductive FunctionsTunica Vaginalis Is a serous membraneLines scrotal cavityReduces friction between opposing surfacesParietal (scrotal)Visceral (testicular)28-2 Male Reproductive FunctionsThe Dartos Muscle Is a layer of smooth muscle in dermis of scrotumCauses characteristic wrinkling of scrotal surfaceThe Cremaster MuscleIs a layer of skeletal muscle deep to dermisTenses scrotum and pulls testes closer to body (temperature regulation)28-2 Male Reproductive FunctionsTemperature Regulation Normal sperm development in testesRequires temperatures 1.1C (2F) lower than body temperature Muscles relax or contractTo move testes away or toward bodyTo maintain acceptable testicular temperatures28-2 Male Reproductive FunctionsStructure of the TestesTunica AlbugineaIs deep to tunica vaginalis A dense layer of connective tissue rich in collagen fibersContinuous with fibers surrounding epididymisFibers extend into substance of testis and form fibrous partitions, or septa, that converge near entrance to epididymisSupports blood and lymphatic vessels of testis and efferent ductules28-2 Male Reproductive FunctionsHistology of the TestesSepta subdivide testis into lobulesLobules contain about 800 slender and tightly coiled seminiferous tubules Produce spermEach is about 80 cm (32 in.) longTestis contains about 1/2 mile of tightly coiled seminiferous tubulesForm a loop connected to rete testis, a network of passageways28-2 Male Reproductive FunctionsEfferent Ductules 15–20 large efferent ductulesConnect rete testis to epididymis28-2 Male Reproductive FunctionsConnective Tissue Capsules Surround tubulesAreolar tissue fills spaces between tubulesWithin those spaces, there are:Blood vesselsLarge interstitial cells (Leydig cells)Produce androgens, dominant male sex hormonesTestosterone is the most important androgen28-2 Male Reproductive FunctionsSpermatogenesis Is the process of sperm productionBegins at outermost cell layer in seminiferous tubulesProceeds toward lumen28-2 Male Reproductive FunctionsCells of Spermatogenesis Spermatogonia (stem cells) divide by mitosis to produce two daughter cellsOne remains as spermatogoniumSecond differentiates into primary spermatocytePrimary spermatocytes begin meiosis and form secondary spermatocytes 28-2 Male Reproductive FunctionsCells of Spermatogenesis Secondary spermatocytes differentiate into spermatids (immature gametes)SpermatidsDifferentiate into spermatozoaSpermatozoaLose contact with wall of seminiferous tubuleEnter fluid in lumen28-2 Male Reproductive FunctionsContents of Seminiferous Tubules SpermatogoniaSpermatocytes at various stages of meiosisSpermatidsSpermatozoaLarge nurse cells (also called sustentacular cells or Sertoli cells)Are attached to tubular capsuleExtend to lumen between other types of cells28-2 Male Reproductive FunctionsSpermatogenesis Involves three integrated processesMitosisMeiosisSpermiogenesis28-2 Male Reproductive FunctionsMitosis Is part of somatic cell divisionProduces two diploid (2n) daughter cellsBoth have identical pairs of chromosomes28-2 Male Reproductive FunctionsMeiosis Is a special form of cell division involved only in production of gametesSpermatozoa in malesOocytes in femalesGametes contain 23 chromosomes, half the normal amount Fusion of male and female gametes produces zygote with 46 chromosomes In seminiferous tubules:Begins with primary spermatocytesProduces spermatids (undifferentiated male gametes)28-2 Male Reproductive FunctionsSpermiogenesis Begins with spermatidsSmall, relatively unspecialized cellsInvolves major structural changesSpermatids differentiate into mature spermatozoaHighly specialized cells28-2 Male Reproductive FunctionsMitosis and MeiosisMeiosis I and meiosis IIProduce four haploid cells, each with 23 chromosomes (n)28-2 Male Reproductive FunctionsMitosis and MeiosisProphase IChromosomes condense Each chromosome has two chromatidsSynapsisMaternal and paternal chromosomes come togetherFour matched chromatids form tetradCrossing over: exchange of genetic material that increases genetic variation among offspring28-2 Male Reproductive FunctionsMitosis and MeiosisMetaphase ITetrads line up along metaphase plateIndependent assortment As each tetrad splits:Maternal and paternal components are randomly distributed 28-2 Male Reproductive FunctionsMitosis and MeiosisAnaphase IMaternal and paternal chromosomes separateEach daughter cell receives whole chromosomeMaternal or paternal28-2 Male Reproductive FunctionsMitosis and Meiosis Telophase I endsWith formation of two daughter cellsWith unique combinations of chromosomesBoth cells contain 23 chromosomes with two chromatids each (reductional division)28-2 Male Reproductive FunctionsMitosis and Meiosis InterphaseSeparates meiosis I and meiosis IIIs very briefDNA is not replicated28-2 Male Reproductive FunctionsMitosis and Meiosis Meiosis IIProceeds through prophase II and metaphase IIAnaphase IIDuplicate chromatids separateTelophase IIYields four cells, each containing 23 chromosomes (equational division)28-2 Male Reproductive FunctionsSpermiogenesis Is the last step of spermatogenesisEach spermatid matures into one spermatozoon (sperm)Attached to cytoplasm of nurse cells28-2 Male Reproductive FunctionsSpermiation At spermiation, a spermatozoon:Loses attachment to nurse cellEnters lumen of seminiferous tubuleSpermatogonial division to spermiationTakes about nine weeks28-2 Male Reproductive FunctionsNurse Cells Affect:MitosisMeiosisSpermiogenesis in seminiferous tubules28-2 Male Reproductive FunctionsSix Major Functions of Nurse Cells Maintain blood–testis barrier Support mitosis and meiosis Support spermiogenesis Secrete inhibin Secrete androgen-binding protein (ABP) Secrete Müllerian-inhibiting factor (MIF)28-2 Male Reproductive FunctionsMaintenance of Blood–Testis Barrier Blood–testis barrier isolates seminiferous tubulesNurse cells are joined by tight junctions that divide seminiferous tubule into compartmentsOuter basal compartment contains spermatogoniaInner luminal compartment is where meiosis and spermiogenesis occur28-2 Male Reproductive FunctionsSupport of Mitosis and Meiosis Nurse cells are stimulated by:Follicle-stimulating hormone (FSH)TestosteroneStimulated nurse cells promote:Division of spermatogoniaMeiotic divisions of spermatocytes28-2 Male Reproductive FunctionsSupport of Spermiogenesis Nurse cellsSurround and enfold spermatidsProvide nutrients and chemical stimuli for developmentPhagocytize cytoplasm shed by developing spermatids28-2 Male Reproductive FunctionsSecretion of Inhibin Inhibin Is a peptide hormone secreted by nurse cells in response to factors released by spermatozoaDepresses:Pituitary production of FSHHypothalamic secretion of GnRHRegulation of FSH and GnRH by inhibin: Gives nurse cells feedback control of spermatogenesisAfter division, increases inhibin production28-2 Male Reproductive FunctionsSecretion of Androgen-Binding Protein (ABP) Androgen-Binding Protein (ABP) Binds androgens (primarily testosterone)In seminiferous tubule fluidIs important in:Elevating androgen in seminiferous tubulesStimulating spermiogenesisProduction of ABP is stimulated by FSH28-2 Male Reproductive FunctionsSecretion of Müllerian-Inhibiting Factor (MIF) Müllerian-Inhibiting Factor (MIF) Is secreted by nurse cells in developing testesCauses regression of fetal Müllerian (paramesonephric) ductsHelp form uterine tubes and uterus in femalesIn males, inadequate MIF production leads to:Retention of ductsFailure of testes to descend into scrotum28-2 Male Reproductive FunctionsThe Anatomy of a SpermatozoonHeadNeck (attaches head to middle piece)Middle piece Tail28-2 Male Reproductive FunctionsThe Anatomy of a Spermatozoon HeadA flattened ellipse that contains nucleus and chromosomes Acrosome A cap-like compartment at tip of head A membranous compartment that contains enzymes essential to fertilizationMade of fused saccules of spermatid’s Golgi apparatus28-2 Male Reproductive FunctionsThe Anatomy of a Spermatozoon Middle pieceAttached to head by short neck Contains mitochondriaIn spiral around microtubulesActivity provides ATP to move tail28-2 Male Reproductive FunctionsThe Anatomy of a Spermatozoon TailIs the only flagellum in the human bodyIs a whiplike organelleMoves cell from one place to anotherHas complex, corkscrew motion28-2 Male Reproductive FunctionsMature Spermatozoon Lacks:Endoplasmic reticulumGolgi apparatusLysosomes and peroxisomesInclusions and other intracellular structuresLoss of these organelles reduces sperm size and massSperm must absorb nutrients (fructose) from surrounding fluid 28-2 Male Reproductive FunctionsThe Male Reproductive TractSperm maturation Testes produce physically mature spermatozoa that CANNOT fertilize an oocyteOther parts of reproductive system are responsible for:Functional maturation, nourishment, storage, and transport28-2 Male Reproductive FunctionsThe Male Reproductive TractSperm maturation SpermatozoaDetach from nurse cellsAre free in lumen of seminiferous tubuleAre functionally immature Are incapable of locomotion or fertilizationAre moved by cilia lining efferent ductules into the epididymis28-2 Male Reproductive FunctionsThe Epididymis Is the start of male reproductive tractIs a coiled tube almost 7 m (23 ft) longBound to posterior border of testisHas a head, a body, and a tail28-2 Male Reproductive FunctionsEpididymis Head Is proximal to the testisReceives spermatozoa from efferent ductulesEpididymis BodyFrom last efferent ductule to posterior margin of testis Epididymis TailBegins near inferior border of testis where number of coils decreasesRe-curves and ascends to connection with ductus deferensPrimary storage location of spermatozoa28-2 Male Reproductive FunctionsThree Functions of the Epididymis Monitors and adjusts fluid produced by seminiferous tubules Recycles damaged spermatozoa Stores and protects spermatozoaFacilitates functional maturation28-2 Male Reproductive FunctionsSpermatozoa Leaving Epididymis Are mature, but remain immobileTo become motile (actively swimming) and functional:Spermatozoa undergo capacitation28-2 Male Reproductive FunctionsTwo Steps in Capacitation Spermatozoa become motileWhen mixed with secretions of seminal glandsSpermatozoa become capable of fertilizationWhen exposed to female reproductive tract28-2 Male Reproductive FunctionsThe Ductus Deferens (Vas Deferens)Is 40–45 cm (16–18 in.) longBegins at tail of the epididymis and, as part of spermatic cord, ascends through inguinal canalCurves inferiorly along urinary bladderToward prostate gland and seminal glandsLumen enlarges into ampulla Wall contains thick layer of smooth muscle28-2 Male Reproductive FunctionsThe Ductus Deferens Is lined by ciliated epitheliumPeristaltic contractions propel spermatozoa and fluid Can store spermatozoa for several monthsIn state of suspended animation (low metabolic rates)28-2 Male Reproductive FunctionsThe Ejaculatory Duct Is a short passageway (2 cm; less than 1 in.)At junction of ampulla and seminal gland duct Penetrates wall of prostate glandEmpties into urethra28-2 Male Reproductive FunctionsThe Urethra Is used by urinary and reproductive systemsExtends 18–20 cm (7–8 in.) from urinary bladder to tip of penisIs divided into three regions Prostatic Membranous Spongy28-2 Male Reproductive FunctionsThe Accessory GlandsProduce semen, which is a mixture of secretions from many glandsEach with distinctive biochemical characteristicsImportant glands include: Seminal glands Prostate gland Bulbourethral glands28-2 Male Reproductive FunctionsFour Major Functions of Male Glands Activating spermatozoaProviding nutrients spermatozoa need for motilityPropelling spermatozoa and fluids along reproductive tractMainly by peristaltic contractionsProducing buffersTo counteract acidity of urethral and vaginal environments28-2 Male Reproductive FunctionsThe Seminal Glands (Seminal Vesicles)Each gland is about 15 cm (6 in.) long with short side branches from body Are tubular glands coiled and folded into 5 cm by 2.5 cm (2 in. × 1 in.) massAre extremely active secretory glands Produce about 60 percent of semen volume 28-2 Male Reproductive FunctionsSeminal Fluid Has same osmotic concentration as blood plasma but different compositionHigh concentrations of fructose easily metabolized by spermatozoaProstaglandins stimulate smooth muscle contractions (male and female)Fibrinogen forms temporary clot in vaginaIs slightly alkalineTo neutralize acids in prostate gland and vagina28-2 Male Reproductive FunctionsSeminal Fluid Initiates first step in capacitationSpermatozoa begin beating flagella, become highly motileIs discharged into ejaculatory duct at emissionWhen peristaltic contractions are under way Contractions are controlled by sympathetic nervous system28-2 Male Reproductive FunctionsThe Prostate Gland Is a small, muscular organ, about 4 cm (1.6 in.) in diameterEncircles proximal portion of urethraBelow urinary bladderConsists of 30–50 compound tubuloalveolar glandsSurrounded by smooth muscle fibers28-2 Male Reproductive FunctionsProstatic Fluid Is slightly acidicForms 20–30 percent of semen volumeContains antibiotic seminalplasminIs ejected into prostatic urethraBy peristalsis of prostate wall28-2 Male Reproductive FunctionsThe Bulbourethral Glands (Cowper’s Glands)Are compound, tubular mucous glands Round shaped, up to 10 mm (less than 0.5 in.) diameterLocated at base of penisCovered by fascia of urogenital diaphragm28-2 Male Reproductive FunctionsThe Bulbourethral Glands (Cowper’s Glands)Secrete thick, alkaline mucusHelps neutralize urinary acids in urethraLubricates the glans (penis tip)Duct of each gland travels alongside penile urethra and empties into urethral lumen28-2 Male Reproductive FunctionsSemen Typical ejaculation releases 2–5 mL Abnormally low volume may indicate problemsWith prostate gland or seminal glandsSperm countIs taken of semen collected after 36 hours of sexual abstinence Normal range 20–100 million spermatozoa/mL of ejaculate28-2 Male Reproductive FunctionsEjaculate Is the volume of fluid produced by ejaculationContains:SpermatozoaSeminal fluidEnzymesIncluding protease, seminalplasmin, prostatic enzyme, and fibrinolysin28-2 Male Reproductive FunctionsMale External GenitaliaThe penisIs a tubular organ through which distal portion of urethra passesConducts urine to exteriorIntroduces semen into female’s vagina28-2 Male Reproductive FunctionsThe Penis The rootIs the fixed portion that attaches penis to body wallAttachment occurs within urogenital triangle, inferior to pubic symphysisThe body (shaft)Is the tubular, movable portion of the penis Consists of three cylindrical columns of erectile tissueThe glansIs the expanded distal end of penis that surrounds external urethral orifice28-2 Male Reproductive FunctionsDermis of the Penis Contains a layer of smooth muscleA continuation of dartos muscle Underlying areolar tissueAllows skin to move freelySubcutaneous layerContains superficial arteries, veins, and lymphatic vessels28-2 Male Reproductive FunctionsThe Prepuce (Foreskin)Is a fold of skin surrounding tip of penisAttaches to neck and continues over glansPreputial glandsIn skin of neck and inner surface of prepuceSecrete waxy material (smegma) that can support bacteriaCircumcision can help prevent infection28-2 Male Reproductive FunctionsErectile Tissue In body of penis Located deep to areolar tissueIn dense network of elastic fibersThat encircles internal structures of penisConsists of network of vascular channelsIncompletely separated by partitions of elastic connective tissue and smooth muscle fibersIn resting state:Arterial branches are constrictedMuscular partitions are tenseBlood flow into erectile tissue is restricted28-2 Male Reproductive FunctionsThe Corpora Cavernosa Two cylindrical masses of erectile tissueUnder anterior surface of flaccid penis Separated by thin septumEncircled by dense collagenous sheathDiverge at their bases, forming the crura of penisEach crus is bound to ramus of ischium and pubisBy tough connective tissue ligamentsExtend to neck of penisErectile tissue surrounds a central artery28-2 Male Reproductive FunctionsThe Corpus Spongiosum Relatively slender erectile body that surrounds penile urethraExtends from urogenital diaphragm to tip of penis and expands to form the glansIs surrounded by a sheathWith more elastic fibers than corpora cavernosaErectile tissue contains a pair of small arteries 28-2 Male Reproductive FunctionsHormones and Male Reproductive FunctionAnterior lobe of the pituitary gland releases: Follicle-stimulating hormone (FSH)Luteinizing hormone (LH)In response to:Gonadotropin-releasing hormone (GnRH)28-2 Male Reproductive FunctionsGonadotropin-Releasing Hormone Is synthesized in hypothalamusCarried to pituitary by hypophyseal portal systemIs secreted in pulsesAt 60–90 minute intervalsControls rates of secretion of:FSH and LH Testosterone (released in response to LH)28-2 Male Reproductive FunctionsFSH and Testosterone Target nurse cells of seminiferous tubulesNurse cellsPromote spermatogenesis and spermiogenesisSecrete androgen-binding protein (ABP)28-2 Male Reproductive FunctionsNegative Feedback Spermatogenesis is regulated by: GnRH, FSH, and inhibinAs spermatogenesis accelerates:Inhibin secretion increases28-2 Male Reproductive FunctionsInhibin Inhibits FSH productionIn anterior lobe of the pituitary glandSuppresses secretion of GnRHAt hypothalamus28-2 Male Reproductive FunctionsInhibin and FSH Elevated FSH levelsIncrease inhibin productionUntil FSH returns to normalIf FSH declines:Inhibin production fallsFSH production increases28-2 Male Reproductive FunctionsLuteinizing Hormone Targets interstitial cells of testesInduces secretion of: TestosteroneOther androgens 28-2 Male Reproductive FunctionsTestosterone Is the most important androgenStimulates spermatogenesisPromoting functional maturation of spermatozoaAffects CNS functionLibido (sexual drive) and related behaviorsStimulates metabolismEspecially protein synthesisBlood cell formationMuscle growth28-2 Male Reproductive FunctionsTestosterone Establishes male secondary sex characteristicsDistribution of facial hairIncreased muscle mass and body sizeCharacteristic adipose tissue depositsMaintains accessory glands and organs of male reproductive tract28-2 Male Reproductive FunctionsTestosteroneFunctions like other steroid hormonesDiffuses across target cell membrane Binds to intracellular receptorHormone–receptor complexBinds to DNA in nucleusCirculating in bloodstreamBound to one of two types of transport proteinsGonadal steroid-binding globulin (GBG) carries 2/3 of circulating testosteroneAlbumins carry 1/3 of testosterone28-2 Male Reproductive FunctionsTestosterone and Development Production begins around seventh week of fetal development and reaches prenatal peak after six monthsSecretion of Müllerian-inhibiting factor by nurse cells leads to regression of Müllerian ductsEarly surge in testosterone levels stimulates differentiation of male duct system and accessory organs and affects CNS development28-2 Male Reproductive FunctionsTestosterone and Development Testosterone programs hypothalamic centers that control:GnRH, FSH, and LH secretionSexual behaviorsSexual drive28-2 Male Reproductive FunctionsEstradiol Is produced in relatively small amounts (2 ng/dL)70 percent is converted from circulating testosteroneBy enzyme aromatase30 percent is secreted by interstitial and nurse cells of testes28-3 The Female Reproductive SystemThe Female Reproductive System Produces sex hormones and functional gametesProtects and supports developing embryoNourishes newborn infant28-3 The Female Reproductive SystemOrgans of the Female Reproductive System OvariesUterine tubesUterusVaginaExternal genitalia28-3 The Female Reproductive SystemStructural Support Ovaries, uterine tubes, and uterus are enclosed in broad ligamentUterine tubesRun along broad ligamentOpen into pelvic cavity lateral to ovariesThe mesovariumStabilizes position of each ovary28-3 The Female Reproductive SystemOvaries Are small, almond-shaped organs near lateral walls of pelvic cavityThree main functionsProduction of immature female gametes (oocytes)Secretion of female sex hormones (estrogens, progestins)Secretion of inhibin, involved in feedback control of pituitary FSH28-3 The Female Reproductive SystemOvary Support Mesovarium Ovarian ligament extends from uterus to ovarySuspensory ligament extends from ovary to pelvic wallContains the ovarian artery and ovarian veinThese vessels connect to ovary at ovarian hilum, where ovary attaches to mesovarium28-3 The Female Reproductive SystemThe Visceral Peritoneum of the OvaryAlso called germinal epitheliumCovers surface of ovaryConsists of columnar epithelial cellsOverlies tunica albuginea28-3 The Female Reproductive SystemThe Stroma Are interior tissues of ovarySuperficial cortexDeeper medullaGametes are produced in cortex28-3 The Female Reproductive SystemOogenesis Also called ovum productionBegins before birthAccelerates at pubertyEnds at menopause28-3 The Female Reproductive SystemFetal Development Between third and seventh months:Primary oocytes prepare for meiosisStop at prophase of meiosis IAtresiaIs the degeneration of primordial follicles Ovaries have about 2 million primordial follicles at birthEach containing a primary oocyte By puberty:Number drops to about 400,00028-3 The Female Reproductive SystemProcess of Oogenesis Primary oocytes remain in suspended development until pubertyAt puberty:Rising FSH triggers start of ovarian cycleEach month thereafter:Some primary oocytes are stimulated to develop further28-3 The Female Reproductive SystemOogenesis: Two Characteristics of MeiosisCytoplasm of primary oocyte divides unevenlyProducing one ovum (with original cytoplasm)And two or three polar bodies (that disintegrate)Ovary releases secondary oocyte (not mature ovum)Suspended in metaphase of meiosis IIMeiosis is completed upon fertilization28-3 The Female Reproductive SystemThe Ovarian Cycle After sexual maturationA different group of primordial follicles is activated each monthIs divided into:Follicular phase (preovulatory phase)Luteal phase (postovulatory phase)28-3 The Female Reproductive SystemThe Ovarian CycleOvarian follicles Are specialized structures in cortex of ovariesWhere oocyte growth and meiosis I occurPrimary oocytesAre located in outer part of ovarian cortexNear tunica albugineaIn clusters called egg nests28-3 The Female Reproductive SystemPrimordial Follicle Each primary oocyte in an egg nestIs surrounded by follicle cellsPrimary oocyte and follicle cells form a primordial follicle28-3 The Female Reproductive SystemThe Uterine Tubes Also called Fallopian tubes or oviducts Are hollow, muscular tubes about 13 cm (5.2 in.) longTransport oocyte from ovary to uterus28-3 The Female Reproductive SystemThree Segments of the Uterine Tubes InfundibulumAn expanded funnel near ovaryWith fimbriae that extend into pelvic cavity Inner surfaces lined with cilia that beat toward middle segment AmpullaMiddle segment Smooth muscle layers in wall become thicker approaching uterus Isthmus A short segment between ampulla and uterine wall28-3 The Female Reproductive SystemHistology of the Uterine TubeEpithelium lining uterine tubeContains scattered mucin-secreting cellsMucosa is surrounded by concentric layers of smooth muscle28-3 The Female Reproductive SystemUterine Tube and Oocyte Transport Involves ciliary movement and peristaltic contractions in walls of uterine tubeA few hours before ovulation, nerves from hypogastric plexus:“Turn on” beating patternInitiate peristalsisFrom infundibulum to uterine cavityNormally takes three to four days28-3 The Female Reproductive SystemUterine Tube and Fertilization For fertilization to occur:Secondary oocyte must meet spermatozoa during first 12–24 hours Fertilization typically occurs:Near boundary between ampulla and isthmusUterine tube provides nutrient-rich environment by secretions from peg cellsContaining lipids and glycogen Nutrients supply spermatozoa and developing pre-embryo28-3 The Female Reproductive SystemThe Uterus Provides for developing embryo (weeks 1–8) and fetus (week 9 through delivery) Mechanical protectionNutritional supportWaste removal28-3 The Female Reproductive SystemThe Uterus Is pear-shaped7.5 cm long, 5 cm diameter (3 in. × 2 in.)Weighs 50–100 g (1.75–3.5 oz)Normally bends anteriorly near base (anteflexion)In retroflexion, uterus bends backward28-3 The Female Reproductive SystemSuspensory Ligaments of UterusUterosacral ligamentsPrevent inferior–anterior movementRound ligamentsRestrict posterior movementCardinal (lateral) ligamentsPrevent inferior movement28-3 The Female Reproductive SystemUterine Body Is largest portion of uterusEnds at isthmus FundusIs rounded portion of uterine bodySuperior to attachment of uterine tubes28-3 The Female Reproductive SystemCervix Is inferior portion of uterusExtends from isthmus to vaginaDistal end projects about 1.25 cm (0.5 in.) into vaginaExternal osAlso called external orifice of uterusIs surrounded by distal end of cervixLeads into cervical canal28-3 The Female Reproductive SystemCervical Canal Is a constricted passageway opening to uterine cavity of bodyAt internal os (internal orifice)28-3 The Female Reproductive SystemBlood Supply of the Uterus Branches of uterine arteriesArising from branches of internal iliac arteriesOvarian arteriesArising from abdominal aorta Veins and lymphatic vessels28-3 The Female Reproductive SystemNerves of the Uterus Autonomic fibers from hypogastric plexus (sympathetic)Sacral segments S3 and S4 (parasympathetic)Segmental blocksAnesthetic procedure used during laborTarget spinal nerves T10–L128-3 The Female Reproductive SystemThe Uterine Wall Has a thick, outer, muscular myometrium Has a thin, inner, glandular endometrium (mucosa)The perimetrium Is an incomplete serous membraneContinuous with peritoneal lining Covers fundus and posterior surface of uterine body and isthmus28-3 The Female Reproductive SystemThe Myometrium The thickest portion of the uterine wallConstitutes almost 90 percent of the mass of the uterusArranged into longitudinal, circular, and oblique layersProvides force to move fetus out of uterus into vagina28-3 The Female Reproductive SystemThe Endometrium Contributes about 10 percent of uterine mass Glandular and vascular tissues support physiological demands of growing fetusUterine glandsOpen onto endometrial surfaceExtend deep into lamina propriaEstrogen Causes uterine glands, blood vessels, and epithelium to change with phases of monthly uterine cycle28-3 The Female Reproductive SystemTwo Divisions of Endometrium The functional zone Contains most of the uterine glandsContributes most of endometrial thicknessUndergoes dramatic changes in thickness and structure during menstrual cycleThe basilar zone Attaches endometrium to myometriumContains terminal branches of tubular endometrial glands28-3 The Female Reproductive SystemBlood Supply of Endometrium Arcuate arteriesEncircle endometriumRadial arteriesSupply straight arteries (to basilar zone)Supply spiral arteries (to functional zone)28-3 The Female Reproductive SystemCyclical Changes in Endometrium Basilar zone remains relatively constantFunctional zone undergoes cyclical changesIn response to sex hormone levelsProduce characteristic features of uterine cycle28-3 The Female Reproductive SystemThe Uterine Cycle (Menstrual Cycle) Is a repeating series of changes in endometriumLasts from 21 to 35 daysAverage 28 daysResponds to hormones of ovarian cycle Menses and proliferative phaseOccur during ovarian follicular phaseSecretory phaseOccurs during ovarian luteal phase28-3 The Female Reproductive SystemMenses Is the degeneration of functional zoneOccurs in patchesIs caused by constriction of spiral arteriesReducing blood flow, oxygen, and nutrientsWeakened arterial walls ruptureReleasing blood into connective tissues of functional zone28-3 The Female Reproductive SystemMenses Degenerating tissues break away, enter uterine lumenEntire functional zone is lostThrough external os and vaginaOnly functional zone is affectedDeeper, basilar zone is supplied by straight arteries28-3 The Female Reproductive SystemMenstruation Is the process of endometrial sloughingLasts one to seven daysSheds 35–50 mL (1.2–1.7 oz) blood 28-3 The Female Reproductive SystemThe Proliferative Phase Epithelial cells of uterine glandsMultiply and spread across endometrial surfaceRestore integrity of uterine epitheliumFurther growth and vascularizationCompletely restores functional zoneOccurs at same time as:Enlargement of primary and secondary follicles in ovary28-3 The Female Reproductive SystemThe Proliferative Phase Is stimulated and sustained by:Estrogens secreted by developing ovarian folliclesEntire functional zone is highly vascularizedSmall arteriesSpiral toward inner surfaceFrom larger arteries in myometrium28-3 The Female Reproductive SystemThe Secretory Phase Endometrial glands enlarge, increasing rate of secretionArteries of uterine wallElongate and spiral through functional zoneBegins at ovulation and persists as long as corpus luteum remains intactPeaks about 12 days after ovulationGlandular activity declinesGenerally lasts 14 daysEnds as corpus luteum stops producing stimulatory hormones28-3 The Female Reproductive SystemMenarche The first uterine cycleBegins at puberty (age 11–12)Menopause The termination of uterine cyclesAge 45–5528-3 The Female Reproductive SystemAmenorrhea Primary amenorrheaFailure to initiate mensesTransient secondary amenorrheaInterruption of six months or moreCaused by physical or emotional stresses28-3 The Female Reproductive SystemThe Vagina Is an elastic, muscular tubeExtends between cervix and vestibule7.5–9 cm (3–3.6 in.) longHighly distensible28-3 The Female Reproductive SystemThe Vagina Cervix projects into vaginal canalFornix is shallow recess surrounding cervical protrusionLies parallel to:Rectum, posteriorlyUrethra, anteriorly28-3 The Female Reproductive SystemBlood Supply of the Vagina Is through vaginal branches of internal iliac (uterine) arteries and veinsInnervation of the Vagina Hypogastric plexusSacral nervesBranches of pudendal nerve28-3 The Female Reproductive SystemThree Functions of the Vagina Passageway for elimination of menstrual fluidsReceives spermatozoa during sexual intercourseForms inferior portion of birth canal28-3 The Female Reproductive SystemAnatomy and Histology of the VaginaThe Vaginal Wall Contains a network of blood vessels and layers of smooth muscleIs moistened by:Secretions of cervical glandsWater movement across permeable epithelium28-3 The Female Reproductive SystemThe Hymen Is an elastic epithelial foldThat partially blocks entrance to vaginaUsually ruptured by sexual intercourse or tampon usage28-3 The Female Reproductive SystemVaginal Muscles Two bulbospongiosus muscles extend along either side of vaginal entranceVestibular bulbsMasses of erectile tissue that lie beneath the musclesHave same embryological origins as corpus spongiosum of penis28-3 The Female Reproductive SystemThe Vaginal EpitheliumIs nonkeratinized, stratified, and squamous Forms folds (rugae)Changes with ovarian cycleVaginal Lamina Propria Is thick and elasticContains small blood vessels, nerves, and lymph nodes28-3 The Female Reproductive SystemThe Vaginal Mucosa Is surrounded by elastic muscularis layerLayers of smooth muscle fibersArranged in circular and longitudinal bundlesContinuous with uterine myometrium28-3 The Female Reproductive SystemVaginal Bacteria A population of harmless resident bacteriaSupported by nutrients in cervical mucusCreates acidic environmentRestricts growth of many pathogensA Vaginal Smear Is a sample of epithelial cells shed at surface of vaginaUsed to estimate stage in ovarian and uterine cycles28-3 The Female Reproductive SystemThe External GenitaliaVulva (or pudendum)Area containing female external genitalia VestibuleA central space bounded by small folds (labia minora)Covered with smooth, hairless skinUrethra opens into vestibuleAnterior to vaginal entrance28-3 The Female Reproductive SystemParaurethral Glands Also called Skene’s glandsDischarge into urethra near external openingThe Clitoris A small protuberance in vestibuleHas same embryonic structures as penis Extensions of labia minora form prepuce or hood28-3 The Female Reproductive SystemVestibular Glands Lesser vestibular glands Secrete onto exposed surface of vestibuleGreater vestibular glands (or Bartholin’s glands)Secrete into vestibule near vaginal entrance28-3 The Female Reproductive SystemMons Pubis and Labia Majora Form outer limits of vulvaProtect and cover inner structuresContain adipose tissueSebaceous glands and apocrine sweat glandsSecrete onto inner surface of labia majora28-3 The Female Reproductive SystemThe Mammary Glands Secrete milk to nourish an infant (lactation)Are specialized organs of integumentary systemAre controlled by hormones of reproductive system and the placentaLie in pectoral fat pads deep to skin of chestNipple on each breastContains ducts from mammary glands to surfaceAreolaReddish-brown skin around each nipple28-3 The Female Reproductive SystemMammary Glands Consist of lobesEach containing several secretory lobulesSeparated by dense connective tissue28-3 The Female Reproductive SystemSuspensory Ligaments of the Breast Bands of connective tissueOriginate in dermis of overlying skinAreolar tissue separates mammary gland complex from underlying pectoralis musclesBlood Supply of Mammary GlandsBranches of internal thoracic artery28-3 The Female Reproductive SystemMammary Gland Ducts Leave lobulesConvergeForm single lactiferous duct in each lobeLactiferous Duct EnlargesForms expanded chamber (lactiferous sinus)15–20 lactiferous sinuses open to each nipple28-3 The Female Reproductive SystemAn Active Mammary Gland Is a tubuloalveolar glandConsisting of multiple glandular tubesEnding in secretory alveoliDoes not complete development unless pregnancy occurs28-3 The Female Reproductive SystemHormones and the Female Reproductive CycleInvolve secretions of pituitary gland and gonadsForm a complex pattern that coordinates ovarian and uterine cyclesCirculating hormones Control female reproductive cycleCoordinate ovulation and uterus preparation28-3 The Female Reproductive SystemHormones and the Female Reproductive CycleGnRH from the hypothalamus regulates reproductive functionGnRH pulse frequency and amplitude change over course of ovarian cycleChanges in GnRH pulse frequency are controlled by: Estrogens that increase pulse frequencyProgestins that decrease pulse frequency28-3 The Female Reproductive SystemThe Endocrine Cells Of anterior lobe of the pituitary Each group of endocrine cells:Responds to different GnRH pulse frequenciesIs sensitive to some frequencies, insensitive to others28-3 The Female Reproductive SystemHormones and the Follicular PhaseBegins with FSH stimulationMonthlySome primordial follicles develop into primary folliclesAs follicles enlarge:Thecal cells produce androstenedione28-3 The Female Reproductive SystemAndrostenedione Is a steroid hormoneIs an intermediate in synthesis of estrogens and androgensIs absorbed by granulosa cells and converted to estrogens28-3 The Female Reproductive SystemInterstitial Cells Scattered throughout ovarian stromaAlso secrete small amounts of estrogensCirculating estrogens Are bound primarily to albuminsLesser amounts carried by gonadal steroid-binding globulin (GBG)Three types: estradiol, estrone, and estriol28-3 The Female Reproductive SystemEstradiolIs most abundant Has most pronounced effects on target tissues Is dominant hormone prior to ovulation28-3 The Female Reproductive SystemEstrogen Synthesis Androstenedione is converted to testosteroneEnzyme aromatase converts testosterone to estradiolEstrone and estriol are synthesized from androstenedione28-3 The Female Reproductive SystemFive Functions of Estrogen Stimulates bone and muscle growthMaintains female secondary sex characteristicsSuch as body hair distribution and adipose tissue depositsAffects central nervous system (CNS) activity Especially in the hypothalamus, where estrogens increase the sexual driveMaintains functional accessory reproductive glands and organsInitiates repair and growth of endometrium28-3 The Female Reproductive SystemSummary: Hormonal Regulation of the Female Reproductive Cycle Early in follicular phase of ovarian cycle:Estrogen levels are lowGnRH pulse frequency is 16–24/day (1 per 60–90 minutes)As tertiary follicles form, concentration of circulating estrogens rises steeply And GnRH pulse frequency increases to 36/day (1 per 30–60 minutes)28-3 The Female Reproductive SystemSummary: Hormonal Regulation of the Female Reproductive Cycle In follicular phase:Switchover occursWhen estrogen levels exceed threshold value for about 36 hoursResulting in massive release of LH from the anterior lobe of the pituitary gland28-3 The Female Reproductive SystemSummary: Hormonal Regulation of the Female Reproductive Cycle In follicular phase:Sudden surge in LH concentration triggers:Completion of meiosis I by primary oocyteRupture of follicular wallOvulationOvulation occurs 34–38 hours after LH surge begins (nine hours after LH peak)28-3 The Female Reproductive SystemSummary: Hormonal Regulation of the Female Reproductive Cycle In luteal phase of ovarian cycle:High LH levels trigger ovulationPromote progesterone secretionTrigger formation of corpus luteumFrequency of GnRH pulses stimulates LH more than FSHLH maintains structure and secretory function of corpus luteum28-3 The Female Reproductive SystemSummary: Hormonal Regulation of the Female Reproductive Cycle Luteal phaseProgesterone levels remain high for one weekUnless pregnancy occurs, corpus luteum begins to degenerateProgesterone and estrogen levels dropGnRH pulse frequency increasesStimulating FSH secretion Ovarian cycle begins again28-3 The Female Reproductive SystemHormones and the Uterine Cycle Corpus luteum degenerates Progesterone and estrogen levels declineResulting in mensesEndometrial tissue sheds several daysUntil rising estrogen stimulates regeneration of functional zone28-3 The Female Reproductive SystemHormones and the Uterine Cycle Proliferative phase continuesUntil rising progesterone starts secretory phaseIncrease in estrogen and progesteroneCauses enlargement of endometrial glandsAnd increase in secretory activities28-3 The Female Reproductive SystemHormones and Body Temperature Monthly hormonal fluctuations affect core body temperatureDuring luteal phase, progesterone dominatesDuring follicular phase, estrogen dominates and basal body temperature decreases about 0.3C Upon ovulation, basal body temperature (BBT) declines noticeablyDay after ovulation, temperature rises28-4 Sexual FunctionAutonomic Function Controls the Reproductive SystemCoitus (Copulation) Sexual intercourseIntroduces semen into female reproductive tract28-4 Sexual FunctionMale Sexual Function Is coordinated by complex neural reflexesUsing sympathetic and parasympathetic divisions of ANSMale sexual arousalLeads to increase in parasympathetic outflow over pelvic nerves, which leads to erection28-4 Sexual FunctionMale Sexual Stimulation Initiates secretion of bulbourethral glandsLubricates penile urethra and surface of glansLeads to coordinated processes of emission and ejaculation28-4 Sexual FunctionEmission Occurs under sympathetic stimulationPeristaltic contractions of ampullaPush fluid and spermatozoa into prostatic urethraSeminal glands contractIncreasing in force and duration Peristaltic contractions in prostate glandMove seminal mixture into urethraSympathetic contraction of urinary bladder and internal urethral sphincterPrevents passage of semen into bladder28-4 Sexual FunctionEjaculation Occurs as powerful, rhythmic contractionsIn ischiocavernosus and bulbospongiosus musclesThat stiffen penisPush semen toward external urethral openingCauses pleasurable sensations (orgasm)Followed by subsidence of erectile tissue (detumescence)28-4 Sexual FunctionImpotence Also called male sexual dysfunctionIs an inability to achieve or maintain an erectionCaused by physical or psychological factors28-4 Sexual FunctionFemale Sexual FunctionParasympathetic activation leads to:Engorgement of erectile tissuesIncreased secretion of cervical mucous glands and greater vestibular glandsBlood vessels in vaginal walls fill with blood Fluid moves from underlying connective tissuesTo vaginal surfaces28-4 Sexual FunctionFemale Orgasm Is accompanied by:Peristaltic contractions of uterine and vaginal wallsRhythmic contractions of bulbospongiosus and ischiocavernosus muscles28-4 Sexual FunctionSexually Transmitted Diseases (STDs) Are transferred by sexual intercourseInclude bacterial, viral, and fungal infectionsPelvic inflammatory disease (PID)AIDSGonorrheaSyphilisHerpesGenital wartsChancroid28-5 Effects of Aging on the Reproductive SystemEffects of AgingFemale reproductive systemChanges associated with menopauseMale reproductive systemChanges associated with male climacteric (andropause) Occur gradually, over longer time period28-5 Effects of Aging on the Reproductive SystemMenopause Is the time that ovulation and menstruation ceaseTypically occurs around age 45–55Circulating concentrations of estrogens and progesterone declineProduction of GnRH, FSH, and LH rises sharply28-5 Effects of Aging on the Reproductive SystemPerimenopauseThe interval immediately preceding menopauseOvarian and uterine cycles become irregularDue to shortage of primordial folliclesEstrogen levels declineOvulation is not triggered28-5 Effects of Aging on the Reproductive SystemDecline in Estrogen Levels Leads to: Reduction in uterus and breast sizeThinning of urethral and vaginal epitheliaReduction in bone deposition (osteoporosis)28-5 Effects of Aging on the Reproductive SystemThe Male Climacteric (Andropause)Is the period of declining reproductive function Circulating testosterone begins to declineBetween ages 50 and 60Circulating FSH and LH increaseSperm production continuesSexual activity gradually decreasesWith declining testosterone levels28-6 Sex Hormones and HomeostasisMalesSperm count must be adequateSemen must have correct pH and nutrientsErection and ejaculation must function properly28-6 Sex Hormones and HomeostasisFemalesOvarian and uterine cycles must coordinate properlyOvulation and oocyte transport must occur normallyEnvironment of reproductive tract must support:Survival and movement of spermFertilization of oocyte28-6 Reproductive System IntegrationHuman Reproduction Requires normal function of multiple systemsReproductive systemDigestive systemEndocrine systemNervous systemCardiovascular systemUrinary system ................
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