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Human Reproduction

Human reproduction is a complex process involving the intricate roles of male and female reproductive systems. DNA determines a baby's gender, with XX for females and XY for males, meaning the father ultimately decides the gender. Males produce millions of sperm daily, while females release one egg monthly, requiring precise hormonal coordination. The menstrual cycle has three stages and prepares the uterus for possible fertilization each month. Birth, fetal development, and breastfeeding are crucial aspects of reproduction, affecting the baby's health and the mother-child bond.

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Human Reproduction

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  1. Human Reproduction

  2. Human Reproductive System Male Female

  3. Male or Female??? • DNA determines baby’s gender • XX = Female • XY = Male • Depends on which egg & sperm get together. • Father determines baby’s gender.

  4. Male Uncomplicated Produce sperm 2-4 MILLION every day Female Very Complicated! One egg Once a month Careful coordination of hormones & body Timing perfect!

  5. Females • Ovaries • 2 pouches • Contain ova • Born with all of her eggs (~ 400,000) • Use up ~500 • Won’t run out! • Ovulation • One egg released from ovary to oviduct (fallopian tube)

  6. After Ovulation • Egg pushed along by cilia • Few days travel time to arrive in uterus • Cervix – Opening between uterus & vagina • Normally tiny • At birth – muscles pull open (dilation) cervix to allow baby to pass through = Labor

  7. Menstrual Cycle • Complex combination of 10-12 chemicals (hormones) • Usually one egg once a month • All about timing!!! • Uterus must be ready when egg gets there in case it was fertilized • If no fertilization, tear down lining of uterus and rebuild for next month

  8. 28-Day Cycle (average) • Three Stages • Tear Down • Rebuild • Extra nutrients/blood for potential baby • No Baby? • Back to #1

  9. Chemicals (hormones) • Regulate events in the body • Estrogen • Progesterone • Many others

  10. Day 1 • First menstrual blood & tissue • No baby = breaks down lining of uterus • 5-7 days of blood/tissue exits body Pre-Ovulation

  11. ~Day 14 • Ovulation = Egg released • Temp spikes slightly • Most fertile in next few days! • Able to get pregnant • Egg gets fertilized while traveling through oviduct. Post-Ovulation

  12. If fertilized… • Zygote begins to divide as it travels through oviduct • Implants into lining of uterus

  13. If not fertilized… • Egg travels through oviduct to uterus • Exits body with blood and tissues during menstruation

  14. Birth Control Pills • “Trick” body into thinking it’s pregnant • Extra hormones • No ovulation occurs • No ovulation = no egg = no fertilization = no baby!

  15. Male • Testes • Produce 2-4 million sperm every day • Outside body – why? • Sperm like temps 1-2 cooler than body temp • Vas Deferens • Tube sperm travel through

  16. Semen • Contains • 300-500 million sperm • Sperm food • pH buffers • Allows sperm to survive for a couple of days inside female’s body

  17. Now… • Contains Several Parts: • Head • Chemical to dissolve egg goo • Dad’s genetic information (DNA) • Mitochondria • Energy • Tail • Swimming

  18. Prostate Gland • Adds stuff to semen • pH buffers • Nourishment

  19. Conception/Fertilization

  20. Conception/Fertilization • Ejaculation • Release of 300-500 million sperm • Egg needs to be in oviduct • Sperm to egg, not an easy task • Go wrong direction : 2 paths – only 1 leads to an egg • Get attacked by female’s white blood cells • Acidic environment • Current

  21. Once egg is located… • Dissolve protective goo surrounding egg • One gets through – enters egg • Instant biochemical change in zygote • No more sperm allowed in

  22. Gamete – Sex cell; sperm and ova • Zygote – Cell formed after male and female gametes join immediately following fertilization

  23. Zygote begins development

  24. Implants in uterine lining • Blastocyst implants in outer lining of uterus • Uses mother’s nutrients • Continues development

  25. Fetal Development • Anmion • Membrane surrounding baby • Contains amniotic fluid • Breaks just before birth = “water broke” • Amniotic Fluid • The “water” – surrounding baby • Buoyant cradle for baby • Protection • Free movement

  26. Fetal Dev (cont’d) • Umbilical Cord • Blood vessels from placenta to baby • Mom’s & baby’s blood do not circulate together! • Can have 2 different blood types • Diffusion

  27. Birth • Labor – muscles used to open cervix • Baby flips upside down • Head first! • Feet first = Breech (bad) • Cesarian Section (“C-section”) surgical removal of baby • After baby is born mom delivers placenta (“afterbirth”) that detaches from uterus

  28. Breastfeeding • Most nutritious option for baby • Milk changes as baby grows • Antibodies from mom create immunity for baby • Studies have shown correlation between breastfeeding and higher intelligence in baby. • Bond w/baby is stronger

  29. Twins/Multiple Births • Two types • Monozygotic • From one egg • Identical • Dizygotic • From two eggs • Fraternal • Not identical

  30. Identical twins • One zygote • Splits in 2 • No one knows why! • Completely random = does NOT run in families • Same exact DNA • Nature’s clones

  31. Fraternal Twins • 2 separate eggs get fertilized with 2 different sperm cells • More than one egg got released during ovulation • Siblings • Can be sisters • Brothers • Brother and sister • Tends to run in families

  32. Conjoined Twins • Used to be called “Siamese” twins • First well known case was in Siam • Identical twins that never completely separated during development • Sometimes can be separated, depending on what is shared.

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