Question

The iter lies
A. In the third ventricle
B. In the second ventricle
C. Between the third and the fourth ventricles
D. In the lateral ventricles

Answer 1

Hint: Our brain has a ventricular system of four cavities that are connected to each other. These cavities are known as ventricles. Within these cavities, cerebrospinal fluid (CSF) is circulated in a region called choroid plexus. CSF is circulated with the help of the central canal of the spinal cord. CSF helps in communication or passage of information.

Complete answer:
There are four ventricles present in this system, namely two lateral ventricles (right and left ventricle, one in each hemisphere), third ventricle, and fourth ventricle. The lateral ventricles are the largest one which is present in the cerebrum, third ventricle is present in the diencephalon region of the forebrain, and the fourth ventricle is present at the backside of pons. The main purpose of these ventricles is the production and circulation of CSF. These ventricles are connected through openings that act as channels between them. This opening connects lateral ventricles to the third ventricle and allows the flow of CSF between them.
Iter, also known as the aqueduct of Sylvius, is present between the third and fourth ventricle. It is found in the mesencephalon region (midbrain) and connects the third ventricle with the fourth ventricle to allow the flow of cerebrospinal fluid within the mesencephalon and metencephalon regions.

Thus, the correct option is (C) Between the third and the fourth ventricles.

Note:
We know that the CSF flows through the ventricles. If these ventricles get narrowed or blocked, this increases the pressure inside the lateral ventricles, and leads to hemorrhagic stroke. This is a serious medical condition for which endoscopic surgery is used for its treatment. Some other diseases of the ventricle system are infection or inflammation of its membrane causing brain hemorrhage.