Date post: | 01-Nov-2014 |
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Embryogenesis of the ChickThe First 72 h
Many of the embryonic images will be from: http://www.uoguelph.ca/zoology/devobio/dbindex.htm
Topics• Diapause• Gastrulation• Primitive Streak• Embryo @ 24 h• Embryo @48 h• Embryo @ 72 h• Hamburger-Hamilton Stages of
Development
Diapause
• Period of time between oviposition and incubation
• Physical Egg Conditions, – Embryo & Cell Division
– Storage Conditions
– Turkey Eggs
Gastrulation in a Microlecithal Egg
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Images from: http://www.uoguelph.ca/zoology/devobio/210labs/gastrulation1.html
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blue=Ectoderm red=Mesoderm yellow=Endoderm
AP=Animal Pole; VP=vegetal
Gastrulation in the Chicken
Gastrulation in the Chicken, cont.
Gastrulation in the Chicken, cont.
a. All embryonic layers originate from Epiblast
b. At gastrulation, cells from Epiblast migrate down between Epiblast & Hypoblast
c. Presumptive Mesodermal cells remain between Epiblast & Hypoblast
d. Presumptive Endoderm formed by cells migrating down into Hypoblast
Primary Germ layer Completion
Gastrulation in the Chicken, cont.
Epiblast gives rise to all 3 Germ Layers
Where do Cells on the Surface of the Blastoderm end up (in Germ Layers)
Presumptive areas studied by;
1. Marking with Dye
a. India Ink injectiondye picked up by cells
b. Radioisotope labeling of an embryo
c. Transplantation of labeled blastoderm
Primary Embryonic Tissue Layers
• What types of tissues and organs result from the formation of the Ectoderm; Mesoderm; and Ento/Endoderm?
24 h Embryo
33 h Developments• Erythrocytes form in extraembryonic mesoderm,
• Appear in patches, blood islets/islands (BI)
• BI’s caudal to the embryo
• Peripheral cells of BI aggregates form endothelium that constitute walls of the blood vessel
• Blood vessels constitute vitelline blood supply, extra vascular blood supply
• Heart formation is occurring
33 h Embryo
48 h Embryo
72 h Embryo
1 = Telencephalon
2 = Diencephalon
3 = Mesencephalon
4 = Metencephalon
5 = Myelencephalon
* = Otic capsule
^ = Olfactory pit
Staging Embryos,
Hamburger Hamilton Stages