Y khoa, y dược - The reproductive system: Part B

27 The Reproductive System: Part BHormonal Regulation of Male Reproductive FunctionA sequence of hormonal regulatory events involving the hypothalamus, anterior pituitary gland, and the testes The hypothalamic-pituitary-gonadal (HPG) axisHPG AxisHypothalamus releases gonadotropin-releasing hormone (GnRH) GnRH stimulates the anterior pituitary to secrete FSH and LHFSH causes sustentacular cells to release androgen-binding protein (ABP), which makes spermatogenic cell receptive to testosteroneLH stimulates interstitial cells to release testosteroneHPG AxisTestosterone is the final trigger for spermatogenesis Feedback inhibition on the hypothalamus and pituitary results fromRising levels of testosteroneInhibin (released when sperm count is high)Figure 27.9AnteriorpituitaryInhibinGnRHTestosteroneVia portalbloodInterstitialcellsSustentacularcellSpermatogeniccellsSeminiferoustubuleSomatic andpsychologicaleffects atother bodysitesLHFSH122345678 Stimulates InhibitsMechanism and Effects of Testosterone ActivityTestosteroneSynthesized from cholesterolTransformed to exert its effects on some target cellsDihydrotestosterone (DHT) in the prostateEstrogen in some neurons in the brainMechanism and Effects of Testosterone ActivityPrompts spermatogenesisTargets all accessory organs; deficiency leads to atrophyHas multiple anabolic effects throughout the bodyIs the basis of the sex drive (libido) in malesMale Secondary Sex CharacteristicsFeatures induced in the nonreproductive organs by male sex hormones (mainly testosterone)Appearance of pubic, axillary, and facial hairEnhanced growth of the chest and deepening of the voiceSkin thickens and becomes oilyBones grow and increase in densitySkeletal muscles increase in size and massFemale Reproductive AnatomyOvaries: female gonadsProduce female gametes (ova)Secrete female sex hormones (estrogen and progesterone)Accessory ducts include Uterine tubesUterusVaginaFemale Reproductive AnatomyInternal genitaliaOvaries Uterine tubes UterusVagina External genitaliaThe external sex organsFigure 27.10PeritoneumInfundibulumUterine tubeOvaryUterusRound ligamentVesicouterine pouchUrinary bladderPubic symphysisMons pubisUrethraClitorisExternal urethralorificeHymenLabium minusLabium majusSuspensoryligament of ovaryUterosacralligamentPerimetriumRectouterinepouchRectumPosterior fornixCervixAnterior fornixVaginaAnusUrogenital diaphragmGreater vestibular(Bartholin’s) glandFimbriaeOvariesHeld in place by several ligamentsOvarian ligament: anchors ovary medially to the uterusSuspensory ligament: anchors ovary laterally to the pelvic wallMesovarium: suspends the ovary Broad ligament: supports the uterine tubes, uterus, and vagina; also contains the suspensory ligament and the mesovariumFigure 27.12aVaginaExternal osCervical canalInternal osWall of uterusPerimetriumMyometriumEndometriumRound ligament of uterusUterinetubeInfundibulumFimbriaeIsthmusAmpullaLumen (cavity)of uterusSuspensoryligament of ovary Uterine (fallopian) tubeOvarian bloodvesselsMesosalpinxMesovariumBroadligament MesometriumOvaryOvarian ligamentBody of uterusUreterUterine blood vesselsIsthmusUterosacral ligamentLateral cervical(cardinal) ligamentLateral fornixCervix(a)Fundusof uterusOvariesBlood supply: ovarian arteries and the ovarian branch of the uterine arterySurrounded by a fibrous tunica albugineaTwo poorly defined regions Cortex: ovarian follicles Medulla: large blood vessels and nervesOvariesFollicleImmature egg (oocyte) surrounded byFollicle cells (one cell layer thick) Granulosa cells (when more than one layer is present)FolliclesSeveral stages of developmentPrimordial follicle: squamouslike follicle cells + oocytePrimary follicle: cuboidal or columnar follicle cells + oocyteSecondary follicle: two or more layers of granulosa cells + oocyte Late secondary follicle: contains fluid-filled space between granulosa cells; coalesces to form a central antrumOvariesVesicular (Graafian) follicleFluid-filled antrum forms; follicle bulges from ovary surfaceOvulationEjection of the oocyte from the ripening follicleCorpus luteum develops from ruptured follicle after ovulationFigure 27.11aMedullaTunicaalbugineaGerminalepitheliumCortexOocyteGranulosa cellsLate secondary follicleAntrumPrimaryfolliclesOocyteZonapellucidaThecafolliculiOvulatedoocyteMesovarium andblood vesselsVesicular(Graafian)follicleCoronaradiataDevelopingcorpus luteumCorpus luteumOvarianligamentDegenerating corpusluteum (corpus albicans)(a) Diagrammatic view of an ovary sectioned to reveal the follicles in its interiorFemale Duct SystemUterine (fallopian) tubes or oviductsUterus VaginaUterine TubesAmpulla Distal expansion with infundibulum near ovaryUsual site of fertilizationCiliated fibriae of infundibulum create currents to move oocyte into uterine tubeIsthmus: constricted region where tube joins uterusUterine TubesOocyte is carried along by peristalsis and ciliary actionNonciliated cells nourish the oocyte and the sperm Mesosalpinx: mesentery that supports the uterine tubesFigure 27.12aVaginaExternal osCervical canalInternal osWall of uterusPerimetriumMyometriumEndometriumRound ligament of uterusUterinetubeInfundibulumFimbriaeIsthmusAmpullaLumen (cavity)of uterusSuspensoryligament of ovary Uterine (fallopian) tubeOvarian bloodvesselsMesosalpinxMesovariumBroadligament MesometriumOvaryOvarian ligamentBody of uterusUreterUterine blood vesselsIsthmusUterosacral ligamentLateral cervical(cardinal) ligamentLateral fornixCervix(a)Fundusof uterusUterusBody: major portion Fundus: rounded superior region Isthmus: narrowed inferior regionUterusCervix: narrow neck, or outlet; projects into the vagina Cervical canal communicates with theVagina via the external osUterine body via the internal osCervical glands secrete mucus that blocks sperm entry except during midcycleSupports of the UterusMesometrium—lateral support: portion of the broad ligamentLateral cervical (cardinal) ligaments: from the cervix and superior part of the vagina to the walls of the pelvisUterosacral ligaments secure uterus to the sacrumRound ligaments bind to the anterior wall Figure 27.12aVaginaExternal osCervical canalInternal osWall of uterusPerimetriumMyometriumEndometriumRound ligament of uterusUterinetubeInfundibulumFimbriaeIsthmusAmpullaLumen (cavity)of uterusSuspensoryligament of ovary Uterine (fallopian) tubeOvarian bloodvesselsMesosalpinxMesovariumBroadligament MesometriumOvaryOvarian ligamentBody of uterusUreterUterine blood vesselsIsthmusUterosacral ligamentLateral cervical(cardinal) ligamentLateral fornixCervix(a)Fundusof uterusPeritoneal PouchesSacs of peritoneum exist around the uterusVesicouterine pouch is between bladder and uterusRectouterine pouch is between rectum and uterusUterine WallThree layersPerimetrium: serous layer (visceral peritoneum)Myometrium: interlacing layers of smooth muscle Endometrium: mucosal lining EndometriumStratum functionalis (functional layer)Changes in response to ovarian hormone cyclesIs shed during menstruationStratum basalis (basal layer)Forms new functionalis after menstruation Unresponsive to ovarian hormonesUterine Vascular SupplyUterine arteries: arise from internal iliacsArcuate arteries: in the myometrium Radial branches in the endometrium branch intoSpiral arteries  stratum functionalisStraight arteries  stratum basalisSpasms of spiral arteries leads to shedding of stratum functionalisFigure 27.13bLumen of uterusUterine glandsSmooth muscle fibersStraight arteryRadial arteryArcuate arteryUterine arteryEndometrial veinCapillariesVenous sinusoidsEpitheliumSpiral (coiled) arteryLamina propria ofconnective tissue(b)VaginaBirth canal and organ of copulation Extends between the bladder and the rectum from the cervix to the exterior Urethra embedded in the anterior wallVaginaLayers of wall Fibroelastic adventitiaSmooth muscle muscularisStratified squamous mucosa with rugaeMucosa near the vaginal orifice forms an incomplete partition called the hymenVaginal fornix: upper end of the vagina surrounding the cervixFigure 27.14aMonspubisPrepuceof clitorisClitoris(glans)VestibuleAnus(a)LabiamajoraLabiaminoraUrethralorificeHymen(ruptured)Opening of the ductof the greater vestibular glandVaginalorificeExternal Genitalia (Vulva or Pudendum)Mons pubis: fatty area overlying pubic symphysis Labia majora: hair-covered, fatty skin folds Labia minora: skin folds lying within labia majoraVestibule: recess between labia minoraExternal GenitaliaGreater vestibular glandsHomologous to the bulbourethral glandsRelease mucus into the vestibule for lubricationExternal GenitaliaClitorisErectile tissue hooded by a prepuceGlans clitoris: exposed portionPerineumDiamond-shaped region between the pubic arch and coccyx Bordered by the ischial tuberosities laterallyFigure 27.14bPubic symphysisLabia minoraClitorisLabia majoraAnusBody of clitoris,containing corporacavernosaClitoris (glans)Crus of clitorisUrethral orificeVaginal orificeGreatervestibularglandFourchetteBulb ofvestibuleInferior ramus of pubis(b)Mammary GlandsModified sweat glands consisting of 15–25 lobes Areola: pigmented skin surrounding the nippleSuspensory ligaments: attach the breast to underlying muscle Lobules within lobes contain glandular alveoli that produce milk Mammary GlandsMilk  lactiferous ducts  lactiferous sinuses  open to the outside at the nippleFigure 27.15Skin (cut)Pectoralis major muscleSuspensory ligamentAdipose tissueLobeAreolaNippleOpening oflactiferous duct Lactiferous sinusLactiferous ductHypodermis(superficial fascia)Intercostal musclesLobule containingalveoli (a)(b)First ribBreast CancerUsually arises from the epithelial cells of small ductsRisk factors include:Early onset of menstruation and late menopauseNo pregnancies or first pregnancy late in lifeFamily history of breast cancer 10% are due to hereditary defects, including mutations to the genes BRCA1 and BRCA2Breast Cancer: Detection and Treatment70% of women with breast cancer have no known risk factorsEarly detection via self-examination and mammographyTreatment depends upon the characteristics of the lesion:Radiation, chemotherapy, and surgery followed by irradiation and chemotherapyFigure 27.16(b) Film of normal breast(a) Mammogram procedure(c) Film of breast with tumorMalignancyOogenesisProduction of female gametesBegins in the fetal periodOogonia (2n ovarian stem cells) multiply by mitosis and store nutrientsPrimary oocytes develop in primordial follicles Primary oocytes begin meiosis but stall in prophase IOogenesisEach month after puberty, a few primary oocytes are activatedOne is selected each month to resume meiosis IResult is two haploid cells Secondary oocyteFirst polar bodyOogenesisThe secondary oocyte arrests in metaphase II and is ovulatedIf penetrated by sperm the second oocyte completes meiosis II, yieldingOvum (the functional gamete)Second polar bodyFigure 27.17Meiotic eventsFollicle developmentin ovaryBefore birthInfancy andchildhood(ovary inactive)Primary oocytePrimary oocyte (stillarrested in prophase I)Vesicular (Graafian)folliclePrimary folliclePrimordial folliclePrimordial follicleOocyteOvulated secondaryoocyteIn absence offertilization, ruptured follicle becomes a corpus luteum andultimately degenerates.Degenatingcorpus luteum Secondary folliclePrimary oocyte(arrested in prophase I;present at birth)Oogonium (stem cell)Each month frompuberty to menopauseMeiosis I (completed by one primary oocyte each month in response to LH surge)First polar bodyMitosisGrowthMeiosis II of polarbody (may or may not occur)Polar bodies(all polar bodiesdegenerate)OvumSecondpolar bodyMeiosis IIcompleted(only if spermpenetration occurs)SpermOvulationSecondary oocyte(arrested in metaphase II)Follicle cellsSpindleOvarian CycleMonthly series of events associated with the maturation of an eggTwo consecutive phases (in a 28-day cycle)Follicular phase: period of follicle growth (days 1–14)Ovulation occurs midcycleLuteal phase: period of corpus luteum activity (days 14–28)Follicular PhasePrimordial follicle becomes primary follicleThe primordial follicle is activatedSquamouslike cells become cuboidalFollicle enlarges to become a primary (1) follicleFigure 27.18 (1 of 7)Theca folliculiPrimary oocyteZona pellucidaAntrumSecondaryoocyte Secondary oocyteCorona radiata12345678Primordialfollicles 1Figure 27.18 (2 of 7)Theca folliculiPrimary oocyteZona pellucidaAntrumSecondaryoocyte Secondary oocyteCorona radiata12345678Primaryfollicle 2Follicular PhasePrimary follicle becomes a secondary follicle Stratified epithelium (granulosa cells) forms around oocyteGranulosa cells and oocyte guide one another’s developmentFollicular PhaseSecondary follicle becomes a late secondary follicleConnective tissue (theca folliculi) and granulosa cells cooperate to produce estrogensZona pellucida forms around the oocyteFluid begins to accumulateFigure 27.18 (3 of 7) Theca folliculiPrimary oocyteZona pellucidaAntrumSecondaryoocyte Secondary oocyteCorona radiata12345678Secondaryfollicle 3Figure 27.18 (4 of 7) Theca folliculiPrimary oocyteZona pellucidaAntrumSecondaryoocyte Secondary oocyteCorona radiata12345678Late secondaryfollicle 4Follicular PhaseLate secondary follicle becomes a vesicular follicleAntrum forms and expands to isolate the oocyte with its corona radiata on a stalkVesicular follicle bulges from the external surface of the ovaryThe primary oocyte completes meiosis IOvulationOvary wall ruptures and expels the secondary oocyte with its corona radiataMittelschmerz: twinge of pain sometimes felt at ovulation1–2% of ovulations release more than one secondary oocyte, which, if fertilized, results in fraternal twins Figure 27.18 (5 of 7)Theca folliculiPrimary oocyteZona pellucidaAntrumSecondaryoocyte Secondary oocyteCorona radiata12345678Mature vesicularfollicle carries out meiosis I; ready to be ovulated5Figure 27.18 (6 of 7)Theca folliculiPrimary oocyteZona pellucidaAntrumSecondaryoocyte Secondary oocyteCorona radiata12345678Follicle ruptures;secondary oocyte ovulated6Luteal PhaseRuptured follicle collapsesGranulosa cells and internal thecal cells form corpus luteumCorpus luteum secretes progesterone and estrogenLuteal PhaseIf no pregnancy, the corpus luteum degenerates into a corpus albicans in 10 daysIf pregnancy occurs, corpus luteum produces hormones until the placenta takes over at about 3 monthsFigure 27.18 (7 of 7)Theca folliculiPrimary oocyteZona pellucidaAntrumSecondaryoocyte Secondary oocyteCorona radiata12345678Corpus luteum(forms from ruptured follicle)7Establishing the Ovarian CycleDuring childhood, ovaries grow and secrete small amounts of estrogens that inhibit the hypothalamic release of GnRHAs puberty nears, GnRH is released; FSH and LH are released by the pituitary, and act on the ovariesThese events continue until an adult cyclic pattern is achieved and menarche occurs