The Fourth Ventricle

The Fourth Ventricle

Question 1. Define the 4th ventricle and discuss its boundaries, communications, and recesses.

Answer.

The 4th ventricle is a tent-like cavity of the hindbrain lined with ependyma. It lies behind the pons and medulla and in front of the cerebellum.

Fourth ventricle

4th Ventricle Boundaries

Lateral (on each side):

• Superolaterally by the superior cerebellar peduncle
• Inferiorly by the inferior cerebellar peduncle

Floor: It is formed by the posterior surfaces of the pons and the upper part of the medulla oblongata. It is rhomboidal in shape; hence, it is often called ‘rhomboid fossa’.

4th ventricle

Roof: It is formed by

• Superior medullary velum, in the upper part
• Inferior medullary velum, in the lower part

Communications Of the 4th Ventricle

It communicates above with the 3rd ventricle through the cerebral aqueduct (aqueduct of Sylvius) and below with the central canal of the spinal cord. Posterolaterally, it communicates with the subarachnoid space through three foramina in its roof (foramen of Magendie and foramina of Luschka).

Cerebral aqueduct

Recesses of the 4th Ventricle. There are five in number:

• Two lateral recesses
• Median dorsal recess
• Two lateral dorsal recesses