DBLecture4posted

DBLecture4posted - Gastrulation The goal is to form three...

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Gastrulation The goal is to form three GERM LAYERS (starting from a hollow ball of cells) Ectoderm: Outside skin, nerves Mesoderm: Blood, Muscle, some organs Endoderm: Inside skin- -gut lining, inside layers of skin
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Gastrulation involves changes in cell shape and changes in cell adhesion
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Cytoskeletal events drive cell shape changes Contraction of the adhesion belt drives apical constriction (see Alberts Fig 20-26 )
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21_24_Adherens_junct.jpg Alberts Fig. 20-25
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21_21_cell_cell_junction.jpg E-cadherin Alberts Fig. 20-22
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Types of Movement in Gastrulation Local inward buckling of an epithelium Inward movement of a cell layer around a point or edge Movement of individual cells or small groups from an epithelium into a cavity Spread of an outside cell layer (as a unit ) to envelop a yolk mass or deeper layer Splitting layers of cells (sometimes used to describe coordinated ingression) Migration Movement of individual cells over other cells or matrix Fig. 5.4 Groups of cells Individual cells
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More complex changes in cell shape can drive elongation or shortening of a flat sheet of cells 15 cells 4 cells Cell intercalation Narrowed and lengthened sheet of cells 30 cells 2 cells Convergent Extension”
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Sea urchin gastrulation Our “simple” model blastocoel Fig. 5.14
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Sea urchin gastrulation Our “simple” model
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Step 1: Primary mesenchyme cells ingress Mesenchyme cells- cells that are unconnected to one another and operate as independent units See also Figure 5.16 Outside (apical) Inside
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Primary mesenchyme ingression is driven by changes in cell adhesion Figure 5.16
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Changes in cell adhesion drive the first step of gastrulation basal lamina and extracellular matrix
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Invaginating primary mesenchyme cells beginning to migrate on the extracellular matrix lining the blastocoel
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Primary mesenchyme cells migrate along the extracellular matrix using filopodia to detect chemical cues
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Primary mesenchyme cells eventually fuse and form the spicules (skeletal rods) Figure 5.17 Figure 5.15
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This note was uploaded on 05/26/2011 for the course BIO 205 taught by Professor Reed during the Spring '11 term at UNC.

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DBLecture4posted - Gastrulation The goal is to form three...

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