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Gastrulation

Gastrulation. Gastrulation - The point in embryogenesis where the basic organization of the organism is established. A. Establishment of the three basic germ layers Ectoderm, Mesoderm, Endoderm

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Gastrulation

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  1. Gastrulation

  2. Gastrulation - The point in embryogenesis where the basic organization of the organism is established. A. Establishment of the three basic germ layers Ectoderm, Mesoderm, Endoderm B. Groups of cells that will give rise to specific organ systems and tissues are moved into the right position both externally and internally. C. Groups of cells that will influence each others differentiation are positioned so they can have an effect on each other.

  3. QUESTIONS? How are layers of tissue established? How do cells get to their proper positions for development? In part, this is accomplished by various types of Morphogenetic Movements.

  4. Morphogenetic Movements Epiboly

  5. Morphogenetic Movements Invagination, Evagination

  6. Involution Morphogenetic Movements Involution Epiboly over a fold

  7. Morphogenetic Movements Delamination

  8. Morphogenetic Movements Ingression

  9. Morphogenetic Movements Cell Migration Cell Migration

  10. Morphogenetic Movements “Intercalation: rows of cells move between one another, creating an array of cells that is longer (in one or more dimensions) but thinner.” “ConvergentExtension: rows of cells intercalate, but the intercalation is highly directional.” - involved in formation of the primitive streak in avian and mammalian embryos. http://biology.kenyon.edu/courses/biol114/Chap14/Chapter_14.html

  11. . . . . . . . . time . . . . . . . . . . . . . . . . . . . . . . . Morphogenetic Movements Differential Growth

  12. Starfish/Sea urchin gastrulation ingression - primary and secondary mesenchyme invagination - initial formation of the archenteron convergent extension - lengthening of the archenteron http://www.gastrulation.org/ http://www.uoguelph.ca/zoology/devobio/210labs/gastrulation1.html http://www.luc.edu/depts/biology/dev/urchgast.htm http://biology.kenyon.edu/courses/biol114/Chap14/Chapter_14.html

  13. Amphibian Gastrulation Urodele blastula (Urodeles, e.g. salamanders)

  14. Urodele 18 - 20 hr

  15. Urodele 18 - 20 hr

  16. Urodele 18 - 20 hr

  17. 28 hr

  18. 38 hr

  19. http://biology.kenyon.edu/courses/biol07/gastmovs.html

  20. 15 hr of time lapse, 48 min/sec http://www.gastrulation.org/

  21. Shell Shell membrane Thin albumin Blastodisk Yolk Chalazae Air pocket http://www.zoomwhales.com/subjects/birds/label/chickenegg/

  22. z The morphogenetic movement that results in elongation of the primitive streak is convergent extension.

  23. Chicken (Avian) Gastrulation Formation of the primitive streak Morphogenetic movement involved in the formation of the primitive streak is convergent extension.

  24. PRIMITIVE STREAK Actually, this is a human embryo. We have the same type of gastrulation as a chicken embryo, yet we do not have a large yolky egg. Why might this be? http://biology.kenyon.edu/courses/biol114/Chap14/Chapter_14A.html

  25. Establishing the Endoderm Extraembryonic endoderm Primary Hypoblast Secondary Hypoblast Embryonic endoderm Derived from cells that are originally in the epiblast that ingress through the primitive streak region and then migrate and insert into the hypoblast layer.

  26. Chicken (Avian) Gastrulation - primary and secondary hypoblast

  27. Yolk Yolk Yolk Yolk Yolk Yolk Yolk Yolk Chicken (Avian) Gastrulation Fate map as gastrulation is beginning

  28. Ingression during avian gastrulation Two regions of ingression: 1. Hensen’s Node 2. Primitive groove

  29. Later, * Hensen’s node will contribute to somites as well *Some cells from Hensen’s node will remain in the epiblast and contribute to neural plate Timing (waves) of ingression: Hensen’s node - initial waves • 1st wave - foregut endoderm (mostly as primitive • streak forms) 2nd wave - head mesoderm 3rd wave - chordamesoderm

  30. Ingression during avian gastrulation Primitive groove 1st wave - rest of embryonic endoderm (mostly as primitive streak forms) 2nd wave - mesoderm (embryonic & extraembryonic)

  31. Chicken (Avian) Gastrulation

  32. Embryonic ectoderm groove embryonic endoderm Chicken (Avian) Gastrulation

  33. Chicken (Avian) Gastrulation - embryonic endoderm

  34. Chicken (Avian) Gastrulation Establishment of the primary germ layers

  35. Chicken (Avian) Gastrulation See animation on digital lab manual

  36. Chicken (Avian) Gastrulation

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