10 



TuDulation ana Extension or tne Major Or^an-rormin^ 

 Areas: Development or Primitive Body Form 



Introduction 



1. Some of the developmental problems faced by the embryo after gastrulation 



a. Tabulation 



b. Increase in size and antero-posteriOr extension of the tubulated, major organ- 

 forming areas 



c. Regional modifications of the tubulated areas 



2. Common, vertebrate, embryonic body form 



3. Starting point for tubulation 



4. Developmental processes which accomplish tubulation 



a. Immediate processes 



b. Auxiliary processes 



5. Blastocoelic space and body-form development 



6. Primitive circulatory tubes or blood vessels 



7. Extra-embryonic membranes 



Tubulation of the neural, epidermal, entodermal, and mesodermal, organ-forming 

 areas in the vertebrate group 



1. Neuralization or the tubulation of the neural plate area 



a. Definition 



b. Neuralizative processes in the Vertehrata 



1) Thickened keel method 



2) Neural fold method 



c. Closure of the blastopore in rounded gastrulae, such as that of the frog 



d. Anterior and posterior neuropores; neurenteric canal 



2. Epidermal tubulation 



a. Development of the epidermal tube in Amphibia 



b. Tubulation of the epidermal area in flat blastoderms 



3. Formation of the primitive gut tube (enteric tubulation) 



a. Regions of primitive gut tube or early metenteron 



b. Formation of the primitive metenteron in the frog 



c. Formation of the tubular metenteron in flat blastoderms 



4. Tubulation (coelom formation) and other features involved in the early differen- 

 tiation of the mesodermal areas 



a. Early changes in the mesodermal areas 



1) Epimere; formation of the somites 



2) Mesomere 



3) Hypomere 



b. Tubulation of the mesodermal areas 



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