diencephalon morphology trait hypothalamus morphology trait Any measurable or observable characteristic related to the shape, structure, color, or pattern of the ventral part of the diencephalon extending from the region of the optic chiasm to the caudal border of the mammillary bodies and forming the inferior and lateral walls of the third ventricle; this region regulates the autonomic nervous system via hormone production and release. Trait.ontology VT:0000837 limbic system morphology trait