The head process (H.P.) is seen as a fairly well defined clump of cells in the middle part of the embryonic plate. There is some body mesoderm which blends with the extra-embryonic layer above the lateral border of the umbilical vesicle. Section 426.
Fig. 23. Heuser et al., 1945.
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Keywords: embryonic plate, head process, mesoderm, umbilical vesicle
Source: The Virtual Human Embryo.