Third Ventricle

Third Ventricle

Question 1. Describe the 3rd ventricle under the following headings:

1. Gross anatomy,
2. Boundaries,
3. Recesses and
4. Applied anatomy.
   

Answer.

The 3rd ventricle is a midline slit-like cavity of the diencephalon, which extends from the lamina terminalis anteriorly to the upper end of the cerebral aqueduct posteriorly. The 3rd ventricle communicates with the lateral ventricles through interventricular foramina (of Monro) and with the 4th ventricle through the cerebral aqueduct (of Sylvius).

3rd Ventricle Boundaries The 3rd ventricle presents an anterior wall, a posterior wall, a floor, a roof, and lateral walls.

• The anterior wall is formed from above downwards by:
  • Anterior column of the fornix
  • Anterior commissure
  • Lamina terminalis
• The posterior wall is formed from above downwards by:
  • Pineal gland
  • Posterior commissure
  • Commencement of the cerebral aqueduct
• The floor is formed from before backwards by:
  • Optic chiasma
  • Tuber cinereum
  • Infundibulum (stalk of the pituitary gland)
  • Mammillary bodies
  • Posterior perforated substance
  • Tegmentum of the midbrain
• The roof is formed by the ependyma stretching across the upper limits of the two thalami.
• The lateral wall is formed by:
  • The medial surface of the anterior two-thirds of the thalamus (forms the lateral wall above the hypothalamic sulcus)
  • The medial surface of the hypothalamus (forms the lower part of the lateral wall below the hypothalamic sulcus)

3rd Ventricle Recesses: These are extensions (pocket-like protrusions) of the cavity of the 3rd ventricle into the surrounding structures:

• Suprapineal recess: Above the stalk of the pineal gland
• Pineal recess: Between the superior and inferior laminae of the stalk of the pineal gland
• Infundibular recess: Into the stalk of the pituitary gland
• Anterior recess (also called the vulva of the ventricle): Between the diverging anterior columns of the fornix in front of the interventricular foramen and behind the anterior commissure

3rd Ventricle Applied Anatomy

• The obstruction of 3rd ventricle leads to the accumulation of excessive CSF in it and two lateral ventricles, which causes an increase in intracranial pressure in adults and hydrocephalus in infants.
• The ventriculography is often done to visualize the obstruction/dilatation of the 3rd ventricle.