Download Blastula – Structure and Fate Map

Blastula –
Structure and
Fate Map
V
1
D
A
First Steps
• “Bottle cells” form at the
vegetal most side of the
organizer by apical
constriction.
V
D
Vg
Apical constriction
and invagination of
Bottle Cells
Invagination:
“the infolding
of a sheet of
cells".
2
Organizer region
• The bottle cells invaginate
into the interior of the
embryo making a dimple.
A
Next Step
• Endodermal and marginal
dorsal cell layers start to
involute into the blastocoel.
V
D
Vg
Organizer region
Involution – of Endodermal and marginal dorsal cell
“A type of cell movement during gastrulation by which an
expanding epithelium turns over on itself and continues to
spread in the opposite direction along its basal margin".
1
3
2
Blastopore Formation
• The surface endodermal
cells and the deep
mesodermal cells continue
to involute and move
towards the animal side.
• At the site of entry an
opening forms – the
blastopore.
Extension and Archenteron Formation
• The involuting layers
elongate by convergent
extension.
4
Convergent Extension
“cell movement resulting in tissue elongation via
intercalation. Two or more rows of cells intercalate, but the
intercalation is highly directional. Cells converge by
intercalating perpendicular to the axis of extension, resulting
in the overall extension of the tissue in a preferred
direction” .
Extension and Archenteron Formation
• The involuting layers
elongate by convergent
extension.
• The archenteron forms
between the involuting
endoderm and the
vegetal inner endoderm.
5
Extension and Archenteron
Formation
• The involuting layers elongate
by convergent extension.
• The archenteron forms between
the involuting endoderm and the
vegetal inner endoderm.
• The animal cells extend to
cover the space left using
epiboly.
Epiboly - of the animal cells
“over the ball", usually the growth of epidermal ectoderm
to cover the surface of the embryo during gastrulation.
6
Blastopore Extension
• The blastopore extends laterally and ventrally.
Dorsal
blastopore lip
Fate Map at Onset of Gastrulation
7
Gastrulation Progression
Apical constriction
and invagination
Involution
Convergent
extension and epiboly
Gastrulation Progression
8
‫פתרון עבודת הכנה לתרגיל ‪Xenopus Gastrulation – 5‬‬
‫™‬
‫על סמך הניסוי של ‪ Vogt‬מהמאה ה ‪) 19‬עמוד ‪ 12‬במהדורה שביעית של ‪Gilbert‬‬
‫”‪ ( “Developmental Biology‬ובהתאם לתהליך תנועות התאים לאורך הגסטרולציה ב ‪,Xenopus‬‬
‫ציינו את מיקומם החדש של התאים השונים בסוף הגסטרולציה )‪.(B‬‬
‫‪Lateral view‬‬
‫‪Dorsal view‬‬
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‫‪D‬‬
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‫‪Dorsal lip‬‬
‫‪Mesoderm‬‬
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‫‪Anus‬‬
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‫‪Ectoderm‬‬
‫‪V‬‬
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‫‪2‬‬
‫‪D‬‬
‫‪Archenteron‬‬
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‫‪A‬‬
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‫‪Head‬‬
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‫‪Endoderm‬‬
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‫‪B‬‬
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