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Fertilization

Fertilization. Fertilization. Joining of sperm & egg sperm head enters egg. Cleavage. Repeated mitotic divisions of zygote 1st step to becoming multicellular unequal divisions establishes body plan

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Fertilization

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  1. Fertilization

  2. Fertilization • Joining of sperm & egg • sperm head enters egg

  3. Cleavage • Repeated mitotic divisions of zygote • 1st step to becoming multicellular • unequal divisions establishes body plan • different cells receive different portions of egg cytoplasm & therefore different regulatory signals

  4. Cleavage • zygote  morula  blastula • establishes future development

  5. Organogenesis Umbilical blood vessels Mammalian embryo Chorion Bird embryo Amnion Yolk sac Allantois Fetal blood vessels Placenta Maternal blood vessels

  6. Placenta • Materials exchange across membranes

  7. Human fetal development 4 weeks 7 weeks

  8. Sex determination Zygote Sperm Develop in early embryo Y Testes XY Ovum X SRY Seminiferous tubules Indifferent gonads Leydig cells No SRY X Ovaries Ovum XX (Follicles do not develop until third trimester) X Sperm Zygote

  9. Human fetal development 10 weeks

  10. Human fetal development 12 weeks 20 weeks

  11. Human fetal development • The fetus just spends much of the 2nd & 3rd trimesters just growing …and doing various flip-turns & kicks inside amniotic fluid Week 20

  12. Human fetal development 24 weeks (6 months; 2nd trimester) fetus is covered with fine, downy hair called lanugo. Its skin is protected by a waxy material called vernix

  13. Human fetal development 30 weeks (7.5 months) umbilical cord

  14. Getting crowded in there!! 32 weeks (8 months) The fetus sleeps 90-95% of the day & sometimes experiences REM sleep, an indication of dreaming

  15. Hormone induction Birth positive feedback

  16. Birth (after 36 weeks) Intestine Placenta Umbilical cord Wall of uterus Bladder Cervix Vagina

  17. The end of the journey!

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