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Human Reproduction

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Reproductive Systems Many similarities between species Most similar within order Basics of initial sperm & egg production, copulation, fertilization the same.

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Male Reproductive Anatomy TestesSperm & testosterone Seminiferous tubules Sperm production EpididymisSperm storage & maturing Vas deferensMoves sperm from dpididymis UrethraMoves sperm & urine outside of body ScrotumSkin sac that contains testes PenisMale copulatory organ

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Male Reproductive Anatomy Seminal vesiclesNutrient fluid Prostate glandAlkaline fluid, prolongs sperm lifespan in female Bulbourethral glands Lubricating fluid Semencombination of sperm & glandular fluids

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Spermatogenesis Begins at 12-14 years old Continues through entire life Under hormonal control Gonadotropin-releasing hormone (GnRH)stimulates other hormones to be released; produced by hypothalamus Follicle-stimulating hormone (FSH)enhances spermatogenesis, not fully understood; anterior pituitary Lutenizing hormone (LH)controls testosterone release; anterior pituitary TestosteroneSexual characteristics & behavior, sperm production InhibinReleased when high sperm count, suppresses other hormones, therefore sperm production.

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Spermatogenesis Occurs in seminiferous tubules in testes Spermatogonia cells Leydig cellsrelease testosterone Germ cells undergo meiosis 1 diploid (2n) 4 haploid (n) cells Sertoli cellsrelease inhibin

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Spermatogenesis Most flagellated (including some plants) Nematodesamoeboid Head Nucleuscontains genetic material Acrosomeenzymes to penetrate egg Midpiece Mitochondria Tail

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Female Reproductive Anatomy Ovariesproduce ovum, reproductive hormones Oviducts (Fallopian tubes)moves ovary to uterus, fertilization Uterushouses embryo Endometriumlining of uterus, supports developing fetus Cervixopening to uterus Vaginabirth canal, copulatory organ

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Oogenesis Begins before birth Continues until menopause Eggs develop to primary oocyte, stopping in prophase I At puberty, oocyte develops into primary follicle Develops to metaphase II and stops (secondary oocyte) Secondary oocyte released during ovulation Remaining follicle becomes corpus luteum, secretes progesterone Secondary oocyte only develops further if fertilized

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Oogenesis Numerous hormones! GnRHtriggers release of LH and FSH; hypothalamus FSHstimulates primary oocytes to develop to next stage; anterior pituitary LHstimulates ovulation, estrogen production; anterior pituitary Estrogenfemale reproductive tract development, sex characteristics; ovary, corpus luteum Progesteronemaintains endometrium; corpus luteum

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Menstrual Cycle MestruationDay 1-5 Low estrogen & progesterone Follicular PhaseDay 6-13 Estrogen increases Endometrium thickens OvulationDay 14 LH & FSH released just prior Mature egg released Luteal PhaseDay 15-28 Corpus luteum increases progesterone Endometrium thickness doubles If no pregnancy, CL degenerates

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Fertilization 150-350 million sperm deposited Only a few hundred reach oviduct Acrosome dissolves outer coating of egg (zona pellucida) Sperm penetrates to egg cell membrane Sperm nucleus enters egg

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Fertilization Once sperm penetrates zona pellucida, cortical granules are released, and move into zona pellucida Zona pellucida hardens, becoming impermeable to any more sperm

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Embryo Development ConceptusFirst 2 weeks Embryo3 rd through 8 th weeks FetusAfter 8 weeks Gestation averages 38 weeks (266 days) Rabbits31 days Dogs & Cats63 days Horses335-340 days Bottlenose Dolphins364-378 days Elephants630-660 days (22 months)

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Embryo Development Zygotefertilized egg, diploid Undergoes cleavage (mitosis) multiple times Travels down oviduct Morulasolid ball of cells

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Embryo Development Morula develops into blastula Blastocoelfluid-filled center Implants in endometrium in later stages Some cells of blastula migrate inside This is where embryo will form Is now a gastrula Ectoderm, endoderm, mesoderm form

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Embryo Development Week 4 Notochord forms Primitive heart tube forms Week 5 Heart develops, begins to beat Limb buds form Earliest stages of organs Week 6 Blood begins flowing Hands and feet developing Week 8 Nipples & hair follicles form Limb movements noticeable

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Fetal Development Weeks 10-13 Face well formed Tooth buds appear Fetus able to make a fist Genitals well differentiated Weeks 14-17 Sucking motions with mouth Lanugo (fine hair) begins to form Week 20 Eyebrows, eyelashes, nails develop Fetal heartbeat heard with stethoscope Mother feels fetus move Lanugo hair covers body

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Fetal Development Week 24 All eye structures developed Fingerprints forming Alveoli forming Responds to sounds Week 28 Respiratory system can exchange gasses Brain growing rapidly Nervous system controlling body functions Premature birth high risk, but possible Opens & closes eyes Week 32 Rhythmic breathing Thalamic connections in brain Bones fully developed

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Fetal Development Weeks 37-40 Considered full term

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