Brainstem components of the ventricular system are visible in this median view of a sheep brain. The third ventricle is indicated by yellow pics. A red pic marks the mesencephalic aqueduct and green indicates the fourth ventricle. Rostrally, the roof of the fourth ventricle (rostral medullary vellum) is thickened by decussating trochlear nerve fibers. The medial wall of the lateral ventricle is evident ventral to corpus callosum (1) in the telencephalon.
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