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Pregnancy & Human Development

Pregnancy & Human Development. Ex. 44. Fertilization: It’s all in the timing!. Oocyte is only viable for ~ 24 hours. Sperm is viable for 12 – 24 hours (some “super sperm” may be viable for up to 72 so be careful!)

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Pregnancy & Human Development

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  1. Pregnancy & Human Development Ex. 44

  2. Fertilization: It’s all in the timing! • Oocyte is only viable for ~ 24 hours. • Sperm is viable for 12 – 24 hours (some “super sperm” may be viable for up to 72 so be careful!) • Therefore, usually, coitus must occur within a 24 hour window on either side of ovulation.

  3. Barriers to fertilization • Low vaginal pH • Getting lost (50/50 chance of getting the right uterine tube) • Numerous defective sperm • Uterine contractions • Phagocytes • By the time they get to the oocyte, there are only a few dozen to a couple hundred

  4. Penetration Secondaryoocyte Head of sperm 1650X

  5. No Polyspermy!

  6. Fertilization&First cleavage

  7. What’s this thing called, Love? • Zygote – a the single cell after fusion of the pronuclei of the oocyte & the sperm. • Conceptus – covers the period of develop following first cleavage and differentiation of cells into an embryo. • Morula – the conceptus as a solid ball of 16 cells (about day 3). • Blastocyst – a hollow ball of cells, from day 4. “Hatching” occurs at this stage, when the blastocyst emerges from the zona pellucida.

  8. Development from zygote to implantation.

  9. Then what ? • The blastocyst differentiates into: • the trophoblast, the outer ball of cells that eventually becomes the placenta and “extraembryonic” membranes. • the inner cell mass (ICM) becomes the embryo. • The above occurs over the course of the second week following conception. • Implantation – occurs on about day 6 or so, as the blastocyst burrows into the endometrium.

  10. Implantation – Day 6

  11. Implantation – Day 7

  12. Hormone levels in early pregnancy

  13. Placental hormones

  14. Implantation

  15. Placentation

  16. Fetus & placenta: 13 weeks

  17. Embryonic Development Differentiation of the three primary germ layers

  18. Germ layer formation, Part II

  19. Neurulation: Part I

  20. Neurulation: Part II

  21. Gastrulation Formation of the primitive gut

  22. Gasturlationpart II

  23. Organogenisisin a 5 week embryo

  24. Differentiation of Mesoderm

  25. Differentiation of Mesoderm continued

  26. The Primary Germ Layers ECTODERM MESODERM ENDODERM

  27. Fetal circulation

  28. Pregnancy from the mother’s perspective

  29. Hey Ma! It’s getting crowded in here!

  30. Labor:the beginning of the end

  31. The “let-down” reflexor, more fun with oxytocin

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