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Chapter 44

Chapter 44. Human Reproduction. Reproductive Systems. Many similarities between species Most similar within order Basics of initial sperm & egg production, copulation, fertilization the same. Male Reproductive Anatomy. Testes —Sperm & testosterone Seminiferous tubules —Sperm production

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Chapter 44

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  1. Chapter 44 Human Reproduction

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

  3. Male Reproductive Anatomy • Testes—Sperm & testosterone • Seminiferous tubules—Sperm production • Epididymis—Sperm storage & maturing • Vas deferens—Moves sperm from dpididymis • Urethra—Moves sperm & urine outside of body • Scrotum—Skin sac that contains testes • Penis—Male copulatory organ

  4. Male Reproductive Anatomy • Seminal vesicles—Nutrient fluid • Prostate gland—Alkaline fluid, prolongs sperm lifespan in female • Bulbourethral glands—Lubricating fluid • Semen—combination of sperm & glandular fluids

  5. 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 • Testosterone—Sexual characteristics & behavior, sperm production • Inhibin—Released when high sperm count, suppresses other hormones, therefore sperm production.

  6. Spermatogenesis • Occurs in seminiferous tubules in testes • Spermatogonia cells • Leydig cells—release testosterone • Germ cells undergo meiosis • 1 diploid (2n) 4 haploid (n) cells • Sertoli cells—release inhibin

  7. Spermatogenesis • Most flagellated (including some plants) • Nematodes—amoeboid • Head • Nucleus—contains genetic material • Acrosome—enzymes to penetrate egg • Midpiece • Mitochondria • Tail

  8. Female Reproductive Anatomy • Ovaries—produce ovum, reproductive hormones • Oviducts (Fallopian tubes)—moves ovary to uterus, fertilization • Uterus—houses embryo • Endometrium—lining of uterus, supports developing fetus • Cervix—opening to uterus • Vagina—birth canal, copulatory organ

  9. 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

  10. Oogenesis • Numerous hormones! • GnRH—triggers release of LH and FSH; hypothalamus • FSH—stimulates primary oocytes to develop to next stage; anterior pituitary • LH—stimulates ovulation, estrogen production; anterior pituitary • Estrogen—female reproductive tract development, sex characteristics; ovary, corpus luteum • Progesterone—maintains endometrium; corpus luteum

  11. Menstrual Cycle • Mestruation—Day 1-5 • Low estrogen & progesterone • Follicular Phase—Day 6-13 • Estrogen increases • Endometrium thickens • Ovulation—Day 14 • LH & FSH released just prior • Mature egg released • Luteal Phase—Day 15-28 • Corpus luteum increases progesterone • Endometrium thickness doubles • If no pregnancy, CL degenerates

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

  13. Fertilization • Once sperm penetrates zonapellucida, cortical granules are released, and move into zonapellucida • Zonapellucida hardens, becoming impermeable to any more sperm

  14. Embryo Development • Conceptus—First 2 weeks • Embryo—3rdthrough 8th weeks • Fetus—After 8 weeks • Gestation averages 38 weeks (266 days) • Rabbits—31 days • Dogs & Cats—63 days • Horses—335-340 days • Bottlenose Dolphins—364-378 days • Elephants—630-660 days (22 months)

  15. Embryo Development • Zygote—fertilized egg, diploid • Undergoes cleavage (mitosis) multiple times • Travels down oviduct • Morula—solid ball of cells

  16. Embryo Development • Morula develops into blastula • Blastocoel—fluid-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

  17. 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

  18. 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

  19. 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

  20. Fetal Development • Weeks 37-40 • Considered full term

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