abnormal floor plate morphology enlarged floor plate 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 expanded floor plate increased floor plate size widened floor plate csmith MPheno.ontology MP:0012675 2014-03-19T09:26:32Z