BILD 2: Multicellular LifeLECTURE #23Website: http://www.biology.ucsd.edu/classes/bild2.WI11.1Instructor: Darwin K. Berg ([email protected])ANNOUNCEMENTS:1) Final Review Session: Wed, Mar 16, 5-8 pm, 3500 Pacific Hall.Building entrance code that day: 701181.2) Final Exam: Fri, Mar 18, 8-10:50 am, WLH 2001.3) Relevant Material for the Final Exam:a) A third devoted exclusively to the last third of the course.b) The remaining two-thirds: comprehensive (entire course).EpididymisSeminiferous tubuleTestisCross sectionof seminiferoustubuleSertoli cellnucleusPrimordial germ cell in embryoMitotic divisionsSpermatogonialstem cellMitotic divisionsMitotic divisionsSpermatogoniumPrimaryspermatocyteMeiosis IMeiosis IISecondary spermatocyteLumen ofseminiferous tubulePlasma membraneTailNeckMidpieceHeadMitochondriaNucleusAcrosomeSpermatids (attwo stages ofdifferentiation)EarlyspermatidDifferentiation(Sertoli cellsprovide nutrients)Sperm2n2n2nnnnn nnnnnnFig. 46-12: Human SpermatogenesisOvaryIn embryoPrimordial germ cellMitotic divisionsOogoniumMitotic divisionsPrimary oocyte(present at birth), arrestedin prophase of meiosis IFirstpolarbodyCompletion of meiosis Iand onset of meiosis IISecondary oocyte,arrested at metaphase ofmeiosis IIOvulation, sperm entryCompletion of meiosis IISecondpolarbodyFertilized eggPrimaryoocytewithinfollicleGrowingfollicleMature follicleRupturedfollicleOvulatedsecondary oocyteCorpus luteumDegeneratingcorpus luteum2n2nnnnnFig. 46-12: Human OogenesisHypothalamusGnRHFSHAnterior pituitarySertoli cellsLeydig cellsInhibinSpermatogenesisTestosteroneTestisLHNegative feedbackNegative feedback–––Fig. 46-13: Hormonal Control of the TestisFig. 46-15: Formation of the Zygote and Early Postfertilization EventsOvaryUterusEndometrium(a) From ovulation to implantation(b) Implantation of blastocystCleavageFertilizationOvulation Cleavagecontinues The blastocystimplantsTrophoblastInner cell massCavityBlastocystEndo-metrium12345Fig. 46-16: Placental CirculationPlacentaUterusUmbilical cordChorionicvillus,containing fetalcapillariesMaternal bloodpoolsMaternalarteriesMaternalveinsMaternalportionof placentaFetal arterioleFetal venuleUmbilical cordFetalportion ofplacenta(chorion)UmbilicalarteriesUmbilicalveinFig. 46-14: TheReproductive Cycle ofthe Human Female(a)Control by hypothalamusHypothalamusGnRHAnterior pituitary1Inhibited by combination ofestradiol and progesteroneStimulated by high levelsof estradiolInhibited by low levels ofestradiol2FSHLHPituitary gonadotropinsin blood(b)6FSHLHFSH and LH stimulatefollicle to growLH surge triggersovulation3Ovarian cycle8(c)7Growing follicleMaturingfollicleCorpusluteumDegeneratingcorpus luteumFollicular phaseOvulationLuteal phaseEstradiol secretedby growing follicle inincreasing amountsProgesterone andestradiol secretedby corpus luteum4Ovarian hormonesin bloodPeak causesLH surge(d)5EstradiolProgesterone910Estradiol levelvery lowProgesterone and estra-diol promote thickeningof endometriumUterine (menstrual) cycleEndometrium(e)Menstrual flow phase Proliferative phaseSecretory phaseDays051014 2025
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