Question

Iter is
a) Part of alimentary canal
b) Connection between third and fourth ventricle
c) Lateral ventricle in cerebrum
d) Ear canal

Answer 1

Hint:It is a connection between two hollow spaces that contain a fluid known as CSF (Cerebrospinal fluid).

Complete answer:
The brain consists of four hollow spaces filled with fluid. These are known as ventricles. CSF (Cerebrospinal spinal fluid) circulates through these ventricles. This fluid helps in maintaining the buoyancy of the brain so that the weight of the brain is not felt. It also acts as a shock absorber. CSF contains glucose, protein, chloride and water.

The four ventricles are connected with each other so that CSF can flow easily. The below diagram shows the four ventricles and connection between them.

The two lateral ventricles are present in the cerebrum. These are also known as Paracoel. Each lateral ventricle lies in one cerebral hemisphere. The two lateral ventricles are separated by septum. Thus the CSF from the two lateral ventricles do not mix with each other. The two lateral ventricles are connected to the third ventricle. This is also known as Diocoel. This lies in the Diencephalon. The connection between lateral and third ventricles is Foramen of Monro or Interventricular foramen. The third ventricle further connects with the fourth ventricle by cerebral aqueduct or aqueduct of Sylvius or Iter. This lies in the midbrain. The fourth ventricle lies in the pons or medulla. The fourth ventricle has three openings through which the CSF circulates in the brain. It is also connected with the central canal of the spinal cord and thus fluid enters the spinal cord also.The CSF is secreted by Choroid plexus present lining the ventricles.

Thus, the answer is, connection between third and fourth ventricle , option C.

Note:A condition known as aqueductal stenosis causes narrowing of this duct. This causes obstruction of the CSF. It is mainly due to tumors. It is congenital in some also.