tuber ci·ne·re·um -si-'nir-ē-əm n an eminence of gray matter which lies on the lower surface of the brain between the optic tracts and in front of the mammillary bodies and of which the upper surface forms part of the floor of the third ventricle and the lower surface bears the infundibulum to which the pituitary gland is attached
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[TA] a layer of gray matter that is part of the hypothalamus; forming a part of the floor of the third ventricle, it lies in front of and between the corpora mammillaria and merges anteriorly into the infundibulum.Medical dictionary. 2011.