Subdivisions of the Hypothalamus

For convenience of description the hypothalamus may be subdivided, roughly, into a number of regions (Figs. 13.16, 13.17). Some authorities divide it (from medial to lateral side) into three zones which are as follows.

a) Periventricular zone.

b) Intermediate zone.

c) Lateral zone.

The periventricular and intermediate zones are often described collectively as the medial zone and we will follow this practice here. The column of the fornix lies between the medial and lateral zones. (The mamillothalamic tract and the fasciculus retroflexus also lie in this plane).

The hypothalamus is also subdivided anteroposteriorly into four regions. These are as follows.

a) Thepreoptic regionadjoins the lamina terminalis.

b) The supraoptic (or chiasmatic) region lies above the optic chiasma.

c) The tuberal (or infundibulotuberal) region includes the infundibulum, the tuber cinereum and the region above it.

d) The mamillary (or posterior) region consists of the mamillary body and the region above it.

The preoptic region differs from the rest of the hypothalamus in being a derivative of the telencephalon. (The lamina terminalis also belongs to the telencephalon).