i. ectoderm. 60 x 1.neural tube3. somite 5. yolk sac 7. aorta 2.amniotic cavity 4. nephrogenic cord...
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BASIC EMBRYONIC BODY PLAN
I. Ectoderm
60- hourchick
embryo15x
60 X
Neural crest development
Neural crest again
Mesoderm
1. Neural tube 3. somite 5. yolk sac 7. aorta2. Amniotic cavity 4. nephrogenic cord 6. notochord 8.
embryonic coelom
Development of the Heart
Splanchnic mesoderm : an area of the endoderm induces development of the cardiogenic mesoderm ; BMP, FGF
Heart and great vessels form from bilaterally paired tubes that fuse in the midline beneath the foregut to produce a single tube
See p. 118, Figure 6-15 Layers of the single tube:
endocardial lining “cardiac jelly” Myocardium Epicardium
The straight tubular heart
Endocardial tubes fuse one tube
Common cardinal veins flow into R and L sinus venosus
Sinus venosus leads to atrium Atrium leads to ventricle Outflow tract = truncus arteriosus
D-loop-- S-shape
See p. 117, Figure 6-14.
Blood and Blood Vessels
Blood islands form in mesodermal wall of yolk sac ( note: extraembryonic )
Blood islands contain hemangioblasts Inducer may be signaling molecule Indian
hedgehog Central part of blood islands
hemocytoblasts Peripheral cells endothelial cells lining the
vessels.
Development of the Endoderm
See Figure 6-20, p. 122 Three divisions: Foregut, Midgut, Hindgut FGF-4 influences devel. of the hindgut Hox genes + retinoic acid regulates
regional development along the digestive tract
1) Flat intraembryonic sheet of endoderm 2) Lateral body folds form that sheet into
a tubular structure 3) Head and Tail folds form foregut,
hindgut
Hox genes determine the form, number, and evolution of repeating parts, such as the number and type of vertebrae in animals with
backbones. In the developing chick (left), the Hoxc-6 gene controls the pattern of the seven thoracic vertebrae (highlighted in
purple), all of which develop ribs. In the garter snake (right), the region controlled by the Hoxc-6 gene (purple) is expanded
dramatically forward to the head and rearward to the cloaca.