General Consideration

Hypothalamus is lower and anterior part of diencephalon. It is the anterior part of ventral diencephalon, posteriorly merging with subthalamus. Hypothalamic sulcus, extending from interventricular foramen of Monro to upper end of aqueduct of Sylvius demarcates hypothalamus from dorsal diencephalon above it.
Hypothalamus being very essential for life, is centrally placed in limbic system below thalamus and overhung by both cerebral hemispheres. Hypothalamus forms the lower part of lateral wall and also the floor of third ventricle of brain which is a central midline cleft.
Part of hypothalamus forming floor of third ventricle of brain forms the components of interpeduncular fossa of base of brain when seen from below.Anteroposteriorly these structures are:

  1. Optic chiasma
  2. Tuber cinereum with infundibulum of pituitary gland (not the gland itself) and
  3. Mammillary body.
How small is hypothalamus:
Hypothalamus is 10 gm in weight and it constitutes only 0.3% of total body mass.
How much important hypothalamus is functionally:
Hypothalamus is very essential for life because almost all the functions of body are controlled by it either directly or indirectly.
Broadly, functions of hypothalamus can be stated as:
  1. It controls activities of autonomic nervous system. Being the supreme center for regulation of autonomic nervous system, hypothalamus had been referred by Sherington as ‘head-ganglion’ of autonomic nervous system.
  2. It controls functions of endocrine system. Thus controlling both autonomic nervous system and endocrine system, hypothalamus maintains body homeostasis.
  3. Hypothalamus plays an important role in emotional activities through its influence on limbic system.
In coronal section, hypothalamus can be simulated with the capital letter ‘U’. Intermediate part of ‘U’ form the floor and, both the limbs form lower part of lateral wall of third ventricle.
So relations of four aspects of hypothalamus are following:
  • Superiorly: Thalamus, demarcated by hypothalamic sulcus.
  • Inferiorly: It is free and form components of interpeduncular fossa of base of the brain. It forms the floor of third ventricle.
  • Medially: Cavity of third ventricle of brain (lower part).
  • Laterally: Internal capsule of brain.

Source: Easy and Interesting Approach to Human Neuroanatomy (Clinically Oriented) (2014)