Embryogenesis of the chicks -------------اجنة 10

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

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Images from: http://www.uoguelph.ca/zoology/devobio/210labs/gastrulation1.html

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

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