Structure of the area membranacea ventriculi IV. In the chick
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In the stage “4 days 12 hrs”, the thin neuroepithelial layer appears to be a direct continuation of the germinal zone pseudostratified epithelium with a gradual mode of transition. Overlapping of cytoplasmic processes, binding the system of cells on the ventricular surface, renders the a.m. epithelium a specialized modification of the internal limiting membrane system.
The neuroepithelial layer possesses, in the central region, a labyrinthine structure with large intercellular spaces. Scanty mesenchymal elements of the intermediate layer are characterized by very long processes. The ectodermal layer consists of flat, relatively dense cells.
The labyrinthine arrangement of neuroectodermal cells, the thin mesenchymal layer, the existence of fine granular material within the intercellular spaces of both neuroectodermal and mesenchymal elements, and the presence of numerous vesicles on the inner surface of the ectodermal cells, indicates the possibility of electrolyte transport between the encephalic and amniotic fluids.
At the stage of 6 days the continuous layer of neuroectodermal cells is interrupted, and a system of intercellular pores appears, establishing a direct communication of the ventricular system with the pericerebral mesenchyme of the future subarachnoid space.
Close correlations between our findings and embryophysiological observations are pointed out and a hypothesis of a regulatory function of the highly specialized structure of the membranous area is assumed.
KeywordsAmniotic Fluid Granular Material Chick Embryo Intercellular Space Cytoplasmic Process
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