Human Reproduction

1. Human Reproduction

2. Battle of the sexes!!! • Are males and females all that different? • Well….. • Yes • And • No!

3. Anatomy Male Female

4. Similarities • 2 pouches • Testicles • Ovaries • Start out inside body • Testicles “descend” before birth • Fetus begins with “starter parts” that could develop into either gender.

5. Around 7th Week… • Baby’s body is “told” by DNA to become either male or female. • “Unused” parts disintegrate • “Used” parts continue development • (see overhead)

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

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

8. 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)

10. 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

11. 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

12. 28-Day Cycle (average) • Three Stages • Tear Down • Rebuild • Extra nutrients/blood for potential baby • No Baby? • Back to #1

13. Chemicals (hormones) • Regulate events in the body • Estrogen • Progesterone • LH (leuteinizing hormone) • FSH (follicle stimulating hormone) • Many others

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

15. ~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

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

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

19. Birth Control Pills • “Trick” body into thinking it’s pregnant • Extra hormones • No ovulation occurs • No ovulation = no egg = no fertilization = no baby! • No hormones taken for 7 days = menstruation

20. 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 • Vasectomy • Cut/tie off tube – sperm can’t get out!

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

22. What is sperm? • Then… • Used to think it was a tiny human inside each cell • Spermists vs. Ovists

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

24. Prostate Gland • Adds non-sperm stuff to semen • pH buffers • Nourishment • Cancer very common • Slower-growing (usually) • Surgery for removal

25. Bulbourethral gland • Adds lubricant to aid travel of semen through the urethra

26. Conception/Fertilization

27. 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

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

29. Zygote begins development Time Lapse Development

30. Implants in uterine lining • Endometrium= outer lining of uterus • Becomes placenta • Uses mother’s nutrients • Continues development

31. 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

33. 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

35. Ancient beliefs • Wak Wak tree

36. 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

37. 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

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

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

40. 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

41. 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.