Question

‘Foramen of Monro’ is present between -
a. Iter and spinocoel
b. Third and fourth ventricle
c. Lateral and third ventricle
d. Diocoel and iter

Answer 1

Hint: Human brain is interiorly formed by the ventricular system. The hollow chambers in the brain are called brain ventricles. These are majorly four in number. The two lateral ventricles ( 1st and 2nd ventricle ), a third ventricle and a fourth ventricle. These ventricles are connected with each other through foramina.

Complete answer:
- The two lateral ventricles are connected with the third ventricle by an interventricular foramen called Foramen of Monro.
- This foramen opens into the third ventricle and is present at the midline of the brain.
- This foramen is roughly semicircular in shape which often becomes round and increases in accordance with size of lateral ventricles.
- The internal walls of the foramen of monro are lined by ependymal epithelial cells and it is bounded anteriorly by structure called fornix and posteriorly by tubercle of thalamus.
- End branches of vessels like medial posterior choroidal artery, superior choroidal vein and septal veins pass through this foramen.
- There is a structure called choroid plexus found in the interior of this foramen that secretes Cerebrospinal fluid ( CSF ). The choroid plexus are the CSF secreting structures found in the ventricular system of the brain.
- The CSF from lateral ventricles enters to the third ventricle through this foramen of monro.

Hence, the correct answer is option (C).

Additional information:
There are another two types of foramina called foramen of luschka and foramen of magendie that connect the third ventricle with the fourth ventricle. The 3rd ventricle is a narrow space which can also easily be obstructed by local brain tumors and these obstructions lead to increased intracranial pressure in adults.

Note: There can be obstruction of this interventricular foramen of monro which can lead to unilateral dilatation of lateral ventricle of that side. Due to this blockage patients present with dementia, headache and can ultimately undergo in coma state.