Summary
The unincubated chick blastoderm, which consists of a complete upper epithelial layer of one cell thickness (epiblast) and an incomplete lower layer (hypoblast), was examined with the electron microscope in order to define the types of cell contact present. The terminal contacts between the cells of the epiblast invariably involved several focal tight junctions, but only occasionally involved tight junctions. Desmosomes were not observed in these areas, but were encountered in various phases of development in the deeper contact regions between epiblast cells. This deeper region also showed sporadic focal tight junctions and frequent micropapillae. These micropapillae were also common on the surfaces of hypoblast cells. Intercellular spaces between epiblast and hypoblast cells and within the hypoblast were often wide, narrowing to occasional focal tight junctions. Tight junctions and desmosomes were not observed in association with hypoblast cells. Gap junctions were not observed in any region of the embryo.
These observations are discussed in relation to the morphogenetic movements occurring in the forming hypoblast and also the influence of this layer on the subsequent development of the embryo. Comparisons are drawn between the contact morphology in the unincubated blastoderm and that in later stages of development.
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Sanders, E.J. Intercellular contact in the unincubated chick embryo. Z.Zellforsch 141, 459–468 (1973). https://doi.org/10.1007/BF00307117
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DOI: https://doi.org/10.1007/BF00307117