Human Reproduction

1. Human Reproduction

2. QOD:1. What is the name of the process by which homologous pairs of chromosomes temporarily join to form tetrads during metaphase one of meiosis?2. What is the name of the process by which homologous pairs of chromosomes separate during anaphase one of meiosis?3. What makes a pair of chromosomes homologous?4. How many sperm are produced when one primary spermatocyte undergoes spermatogenesis?5. How many eggs (ova) are produced when one primary oocyte undergoes oogenesis?

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

5. Male Reproductive Organs

6. Sperm Structure • Parts: • Head • Chemical to dissolve egg outer coating • Dad’s genetic information (DNA) • Mitochondria • Energy • Tail • Swimming

7. Female Reproductive Organs

8. Similarities b/w Males and Females • 2 pouches • Testicles • Ovaries • Start out inside body • Testicles “descend” before birth • Fetus begins with “starter parts” that could develop into either gender.

9. Around 7th Week… • Baby’s body is “told” by DNA to become either male or female.

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

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

12. 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)

13. Menstrual Cycle • Complex combination of 10-12 chemicals (hormones) • Usually one egg once a month • Four Stages: • Follicle Stage • Ovulation • Corpus Luteum • Menstruation • Estrogen • Progesterone • LH (leuteinizing hormone) • FSH (follicle stimulating hormone) • Many others

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

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

17. 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

18. 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!

19. 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)

20. 3 Glands aid in the success of sperm reaching their destination:- Prostate Gland- fluid and nourishment -Bulbourethral gland- lubricant- Seminal vesicle- buffers

21. Conception/Fertilization

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

23. Zygote (undergoes rapid mitotic division called (Cleavage)Morula (solid ball of identical cells)Blastula (hollow ball of cells…implants in lining of uterus)Embryonic stage (8 weeks) Gastrulation (4 weeks) Three cell layers develop: Endoderm- becomes liver, pancreas, digestive liningMesoderm- muscle, skeleton, circ, excre, repro systemEctoderm- epidermis, hair, mouth, nostrils, anusNeurulation/organogenesis (4 weeks) All systems and organs form Fetal stage (week 8 until birth) Time of growth and maturationBirth

24. 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

25. 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

28. 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

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

30. 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

31. 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.

33. Parthenogenesis: a form of reproduction that occurs w/o fertilization. The ovum becomes a new individual who is sterile ex. Female bee- produce a male drone. ****other examples- insects, rotifers, snakes, fish, some species of lizards, rare in plants Sterile animals, like the mule, is due to the fact that they lack a sex chromosome Internal vs. External fertilization Define: Examples: Advantage or disadvantage????