abnormal floor plate morphology enlarged floor plate 2014-03-19T09:26:32Z MP:0012675 MPheno.ontology csmith expanded floor plate increased floor plate size increased size of the specialized glial structure (non-neuronal cells) situated at the ventral midline of the embryonic neural tube; this structure spans the anteroposterior axis from the midbrain to the tail regions, separating the left and right basal plates of the developing neural tube, and serves as an organizer to ventralize tissues in the embryo as well as to guide neuronal positioning and differentiation along the dorsoventral axis of the neural tube widened floor plate