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Chapter 49

Chapter 49. Embryonic Development. Developmental stages of humans. Fertilization Zygote It is a fertilized egg Female pronuclei Male pronuclei Amphimixis. Developmental stages of humans. Zona pellucida Surrounds the zygote Disappears when the blastocyst reaches the uterine cavity

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Chapter 49

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  1. Chapter 49 Embryonic Development

  2. Developmental stages of humans • Fertilization • Zygote • It is a fertilized egg • Female pronuclei • Male pronuclei • Amphimixis

  3. Developmental stages of humans • Zonapellucida • Surrounds the zygote • Disappears when the blastocyst reaches the uterine cavity • Corona radiata • Granulosa cells surrounding the zonapellucicda • Disappears after fertilization

  4. Fertilization

  5. Developmental stages of humans • Cleavage • Stages of the Cleavage • Blastomere • Early cleavage • 4-cells stage… • Morula • 16-32 cells stage

  6. Developmental stages of humans • Blastula • Central cavity appears – blastocystic cavity • Blastocyst • Inner cell mass (ICM) – forms the embryo • Trophoblast – nourishes the developing embryo • Final product of cleavage

  7. Developmental stages of humans • Implantation • From day 7 to day 14 after the ovulation • The blastocyst will go from a floating stage to a complete implanted stage in the uterus • Deciduas basalis-part of the endometrium beneath the ICM. It will form the maternal portion of the placenta

  8. Developmental stages of humans • Deciduas capsularis – it is the rest of endometrium surrounding the blastocyst • Gastrulation • The ICM will develop into three primary germ layers • Ectoderm • Forms the epithelia and nervous system

  9. Developmental stages of humans • Mesoderm • Forms everything between the ectoderm and the endoderm • Endoderm • Forms the mucosa of the digestive and respiratory tract, etc

  10. Developmental stages

  11. Developmental stages of humans • Embryo • Until the 8th week • Fetus • From 8th week to birth • Trophoblast • Will develop villi • Will differentiate into the chorion that will form the fetal portion of the placenta

  12. Developmental stages of humans • Placenta • Chorionic villi + decidua basalis • Embryonic membranes (from the ICM) • Amnion • Encases the embryo • Amniotic cavity • Amniotic fluid

  13. Developmental stages

  14. Developmental stages of humans • Yolk sac • Mesoderm + endoderm • Originates the embryo’s first blood cells • Allantois • Endoderm + mesoderm = body stalk and later umbilical cord • Umbilical cord attaches the embryo to the placenta

  15. In uterus development • Placenta • Fetal side • Shine and smooth • Presence of large blood vessels • Maternal side • Spongy, torn-looking, rough

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