Hypothalamus

The hypothalamus is a subdivision of the diencephalon, located ventrally to the thalamus and medially to the subthalamus. It forms the wall and floor of the third ventricle, dorsally bounded by the hypothalamic sulcus. On its ventral surface, it includes the optic chiasma and optic tract anteriorly, the tuber cinereum and the pituitary gland (hypophysis) in the intermediate position, and the mammillary bodies, separated from the ventricle by the inframammillary recess, posteriorly. Anteriorly, it is bounded by the gray terminal lamina.

The hypothalamus plays a central role in homeostatic control (body temperature, water balance, food intake, circadian rhythms), in endocrine regulation through its connection with the pituitary, as well as in the control of the autonomic nervous system and affective behaviors.

The ventral surface of the hypothalamus is relatively narrow and small in Equids, compared to Ruminants, Carnivores, and Humans. In the latter, the ventral surface is much wider than it is long.