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The First Three Weeks

The First Three Weeks. Thomas A. Marino, Ph.D. Department of Anatomy and Cell Biology Temple University School of Medicine. Introduction. The lecture will focus on the early development of the embryo We will cover the first three weeks after fertilization.

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The First Three Weeks

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  1. The First Three Weeks Thomas A. Marino, Ph.D. Department of Anatomy and Cell Biology Temple University School of Medicine

  2. Introduction • The lecture will focus on the early development of the embryo • We will cover the first three weeks after fertilization. • Will start with a fertilized egg.

  3. Week 1-3: Formation of: • Blastocyst • Bilaminar disc • Gastrulation • Trilaminar disc • Lateral body folding • Head and tail folding • Vertebrate body plan

  4. Week 1: 4 cell stage Late Day 2 Morula Day 3 2 cell stage Day 2 Blastocyst Day 5 Implantation Day 6 - 7 Fertilization Day 1

  5. Early Embryology http://www.infertilitydoctor.com/ivf/ivf_devel.htm PACIFIC FERTILITY CENTER

  6. Inner Cell Mass (embryoblast) Trophoblast Blastocele Week 1 • The blastocyst consists of :

  7. Uterine Artery Uterine Gland Epithelium of Uterus Inner Cell Mass Trophoblast Blastsocele Week 1

  8. Week 2Day 7.5 Inner Cell Mass Blastocyst Cavity Cytotrophoblast Syncytiotrophoblast

  9. Cytotrophoblast Amniotic Cavity Amnioblasts Epiblast Hypoblast Primary Yolk Sac Exocoelomic Membrane Week 2: Early Development Inner Cell Mass:

  10. Human Developmental Anatomy Center - 9 days of Gestation

  11. Syncytiotrophoblast Amniotic Cavity Epiblast Hypoblast Primary yolk sac Exocoelomic membrane Cytotrophoblast Extraembryonic mesoderm Early Development - Week 2Day 10

  12. Week 2: Early Development Lacunae Amniotic Cavity Epiblast Hypoblast Primary yolk sac Exocoelomic membrane Cytotrophoblast Extraembryonic mesoderm

  13. Human Developmental Anatomy Center - 9 days of Gestation

  14. Week 2: Early Development Connecting stalk Cytotrophoblast Epiblast Hypoblast Amniotic Cavity Extraembryonic somatopleuric mesoderm Primary Yolk Sac Extraembryonic splanchnopleuric mesoderm Extraembryonic Coelom

  15. Third Week Extraembryonic Somatopleuric Mesoderm cytotrophoblast Extraembryonic Splanchnopleuric Mesoderm Epiblast Hypoblast Primitive Yolk Sac Extraembryonic Coelom

  16. Human Developmental Anatomy Center

  17. Third Week Bilaminar Disc

  18. Gastrulation Amnion Epiblast Hypoblast Primary Yolk Sac Extraembryonic splanchnic mesoderm

  19. UNSW Embryology 17 – 19 days of gestation

  20. Primitive Node Gastrulation Primitive Streak

  21. Notochord Gastrulation Neural Plate

  22. Gastrulation

  23. Gastrulation Amniotic Cavity Epiblast Primary Yolk Sac Hypoblast

  24. Gastrulation Primitive Node Primitive Pit

  25. Connecting Stalk Gastrulation Notochord Oral Plate Primitive Node Pre(noto)chordal plate Primitive Streak

  26. Gastrulation

  27. Gastrulation Primitive Pit Primitive Node Notochordal Process

  28. Gastrulation

  29. Gastrulation mesoderm ectoderm notochordal canal endoderm notochordal process

  30. Gastrulation Neurenteric Canal Notochordal plate

  31. Gastrulation Notochordal Plate

  32. Gastrulation

  33. Gastrulation Ectoderm Amniotic Cavity Paraxial mesoderm Intermediate mesoderm Lateral plate mesoderm Yolk Sac Notochord Endoderm

  34. Formation of the Body AxisThe cranial end of the embryo • Anterior visceral endoderm (AVE) • OTX, LIM1, HESX1 transcription factors • secreted factor ceberus

  35. Formation of the Body Axis BMP-4 FGF BMP-4 FGF Lateralize Mesoderm: Intermediate and Lateral Plate mesoderm BMP-4 – bone morphogenetic protein-4 with FGF – Fibroblast growth factor

  36. Formation of the Body Axis • Cranial Mesoderm • Notochord • Somites • Somitomeres Goosecoid, chordin Noggin and follistatin Dorsalize mesoderm into Notochord and Paraxial Mesoderm

  37. Formation of the Body Axis Nodal HNF-3b Brachyury (T) gene Forebrain Midbrain Mid and caudal midline mesoderm development

  38. Formation of the Body AxisLeft – Right Sidedness FGF8 Nodal Lefty PITX2

  39. Cilia in Left – Right sidedness • Situs inversus • 20% (Kartagener syndrome) • Dysfunctional cilia • Respiratory problems • Male fertility problems

  40. UNSW Embryology 20 days of gestation

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