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MSU BIO 101 - Human Reproduction
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SimilaritiesA pair of gonads, the organs that produce gametesTesticlesOvariesStart out inside bodyTesticles descend before birthA system of ducts that store and deliver gametesFetus begins with “starter parts” that could develop into either gender.Male or Female?DNA determines baby’s genderIn some species of plants and animals, but not all speciesXX= human femaleXY= Human MaleDepends on which egg and sperm get togetherFather determines baby’s gender in humansAround 7th week…Baby’s body is told by DNA to become either male or femaleUnused pats disintegrateUsed parts continued Development.Human Male anatomyUrine and sperm are conveyed through a tube called the urethraThe penis contains erectile tissue that, when filled with blood, produces an erectionThe male gonad is the testis.The scrotum is an external sac that holds the testes and keeps them slightly cooler than body temperature.Within the testes, diploid cells divide via meiosis to produce haploid sperm cells (23 chromosomes).This is the process of spermatogenesis.Humans have 46 Chromosomes.Human Female anatomyThe ovary is the female gonad, where oocytes are produced and released.The uterus is the site of pregnancy where an embryo develops into a baby.The vagina, or birth canal, is where sperm enters and a baby exitsThe oviduct (fallopian tube) is the site where egg meets spermThe vulva is collective name for all the external female reproductive structures.Within the ovary during the process of oogenesis a mature haploid egg called an ovum develops (23 chromosomes).Formation of an oocyteOvaries2 pouchescontain ovaBorn with all of her eggs (400,000)Use up to 500OvulationTypically only one oocyte is released from ovary to oviduct (fallopian tube).Ovulation, the release of an oocyte cell from the ovaries may occur around day 14.This varies for many women.28-Day Cycle (average)Three Stages1. Tear down2. Rebuild3. Extra nutrients/blood for potential babyNo baby?Back to #1Hormones in the OvariesDay 1-7: Follicles enlarge due to increasing levels of follicle stimulating hormones (FSH)Day 8-13: Enlarging follicle secretes increasing amounts of estrogenDay 14: surge of leutinizing hormone (LH) induces ovulationDay 14-28: Corpus luteum secretes progesterone.After OvulationEgg pushed along the ciliaFew days travel time to arrive in uterusCervis— opening between uterus and vaginaNormally tinyAt birth— muscles pull open (dilation) cervix to allow baby to pass through = labor.Hormones in the UterusDay 0-7: Menstruation due to loss of progesteroneDay 7-14: Thickening of endometrium in response to estrogen.Day 14-28: continued endometrial development in response to progesterone.Mid cycleOvulation= oovum releasedTemp spikes slightlyMot fertile in next few days!Able to get pregnantEgg gets fertilized while traveling through oviduct.EndometriosisEndometriosis is a painful disorder in which the tissue that normally lines the inside of the uterus grows outside your uterus.Displaced endometrial tissue continues to act as normal—it thickens, breaks down, and bleeds with each menstrual cycle. But this broken down tissue has no way to exit the body.When endometriosis involves the ovaries, cysts may form. Surrounding tissue can become irritated, eventually developing scar tissue and adhesions (abnormal tissue that binds organs together). Fertility problems may also develop.MaleTestesProduce 2-4 million sperm every dayOutside body – why?Sperm like temps 1-2° cooler than body tempVas DeferensTube sperm travel throughVasectomyCut/tie off tube – sperm can’t get out!SemenContains300-500 million spermSperm foodpH buffersAllows sperm to survive for a couple of days inside female’s body (hostile environment)What is sperm?Then…Used to think it was a tiny human inside each cellSpermists vs. OvistsNowContains Several Parts:HeadChemical to dissolve egg gooDad’s genetic information (DNA)Body with MitochondriaEnergyTailSwimmingProstate GlandAdds necessary chemicals to support the lives of the sperm to semenpH buffersNourishment, proteins, carbohydratesCancer very commonSlower-growing (usually)Surgery for removalBulbourethral GlandAds lubricant to aid travel of semen through the urethra.Conception/FertilizationEjaculationRelease of 300-500 million spermEgg needs to be in oviductSperm to egg, not an easy taskGo wrong direction : 2 paths – only 1 leads to an eggGet attacked by female’s white blood cellsAcidic environmentCurrentMythIn the traditional model, the oovm passively waits for the sperm’s arrival, and the sperm breaks through the oovm’s protective coat through mechanical burrowing.Now we know both sperm and oovm play active rolesThe oovm :Binds and draws in the sperm as well as blocking out extra sperm.Oovm engulfs sperm by protrusion of cytoplasm.After a sperm makes it through, the egg hardens.The sperm:Tails are actually weak. Side to side motion of tails results in same motion in heads, but far more powerful. As a result, rather than forcefully overcoming the egg’s barrier, the head thrashes as if to move away. The egg holds the head in place.The oovm and sperm must “recognize” one another in order to proceed to fertilization. They have complimentary proteins on their cell surfaces.FertilizationDissolve protective goo surrounding eggOne gets through – enters eggInstant biochemical change in zygoteNo more sperm allowed inImplants in uterine LiningEndometrium is the lining of uterusUses mother’s nutrientsContinues developmentFetal DevelopmentAnmionMembrane surrounding babyContains amniotic fluidBreaks just before birth = “water broke”Amniotic FluidThe “water” – surrounding babyBuoyant cradle for babyProtectionFree movementUmbilical CordBlood vessels from placenta to babyMom’s & baby’s blood do not circulate together!Can have 2 different blood typesDiffusionBirthLabor – muscles used to open cervixBaby flips upside downHead first!Feet first = BreechCesarean Section (“C-section”) surgical removal of babyAfter baby is born mom delivers placenta (“afterbirth”) that detaches from uterusContraceptionMost contraception methods aim to prevent the egg and sperm from joining.For female anatomy, these include diaphragm, tubal ligationFor male anatomy, these include condom, vasectomyHow do Birth Control Pills work?Oral contraceptives contain synthetic hormones that prevent development of an egg in the ovaries.These synthetic hormones trick the ovary into thinking that it’s already released an


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