Figure 1. The location of the hypothalamus in the ventral forebrain is illustrated in midsagittal and ventral exposures of the human brain. (a) The midsagittal exposure reveals the hypothalamus (marked with an asterisk) immediately in front of the midbrain flexure. This same exposure is shown at higher magnification in Figure 2a. (b) The ventral exposure reveals the three major superficial landmarks that mark the position of the hypothalamus in the ventral diencephalon. The most rostral portion is marked by the optic chiasm (OC), which is formed by the convergence of the optic nerves and gives rise to the optic tracts. The pituitary stalk (PS) lies immediately behind the chiasm in the tuberal hypothalamus. The pituitary has been removed from this specimen, revealing the central lumen, which is continuous with the third ventricle. The bilaterally paired mammillary bodies (MB) mark the caudal-most extent of the hypothalamus.

Figure 2. (a) The rostrocaudal extent of the hypothalamus, defined by the optic chiasm (OC) and mammillary body (MB), is shown in midsagittal exposure. (b) The internal structure of hypothalamus as revealed in a myelin-stained transverse section passing through the level of the pituitary stalk. The homogeneous tissue on either side of the third ventricle (V3) constitutes the bilaterally paired cell masses that form the hypothalamus. The relative position of periventricular (P), medial (M) and lateral (L) columns are defined on the left side of the hypothalamus. OT, optic tract: F, fornix.