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1. The layer of cells that develops on the surface of the yolk in an avian or reptilian egg and gives rise to the germinal disk from which the embryo develops.
2. The layer of cells formed by the cleavage of a fertilized mammalian egg. It later divides into the three germ layers from which the embryo develops.
blas′to·der·mat′ic (-dər-măt′ĭk), blas′to·der′mic adj.
nAlso called: blastodisc
1. (Biology) the layer of cells that surrounds the blastocoel of a blastula
2. (Biology) a flat disc of cells formed after cleavage in a heavily yolked egg, such as a bird's egg
1. the primitive layer of cells that results from the segmentation of the ovum.
2. the layer of cells forming the wall of the blastula and in most vertebrates enclosing a cavity or a yolk mass.