Question

Helicotrema is
a. An aquatic mammal
b. An aperture in between the III and IV ventricle of brain
c. An aperture in between two scalae of cochlea of mammal
d. A disease of internal ear

Answer 1

The mammal ear consists of auricle, external auditory canal, tympanic membrane, middle ear contains incus and malleus, and the inner ear contains cochlea. The cochlea includes scala vestibuli, scala tympani and organ of corti. It helps to receive the vibrations and transfer it to the brain.

Complete answer:
The semilunar opening or the part of the cochlea is called a helicotrema which is present where the scala tympani and the scala vestibuli meet. It plays an important role in detecting low frequency sounds with the help of hair cells. Helicotrema is present at the apex of cochlea that is the end of the cochlea. Both the scales communicate through helicotrema as it is connected to the perilymph.

The perilymph-filled cavities in the inner ear of the human are called as tympanic duct or scala tympani. It extends from the round window to the helicotrema and separates from the cochlear duct by the basilar membrane and it continues as a vestibular duct. The vestibular membrane is also called Reissner's membrane.
The helicotrema is not the internal ear disease. It is present in the ear, not in the brain. It is not the name of an aquatic animal.

From the above information we have found that helicotrema is an aperture in between two scales of cochlea of mammals.
Hence, the correct answer is option (C).

Note: The inner ear contains a shell like structure called cochlea. It receives the sound in the form of vibrations, which causes the stereocilia to move. It converts the vibrations into the nerve impulse and transfers it to the brain to interpret the sound. Some of the internal ear diseases are acoustic neuroma, Otosclerosis, middle ear infection, blast injury, etc.