Question

Which part is not included in the cochlear duct?
A. Tectorial membrane
B. Macula of utricle
C. Scala media
D. Reissner's membrane

Answer 1

Hint:- Human ear consists of three parts namely- the external ear, middle ear and inner ear. The external ear is also called the pinna, its major function is to collect the sound waves and transmit them through the external auditory canal towards the middle ear.
In the middle ear, there are presently three small bones called ear ossicles. These ossicles undergo vibration when the sound wave strikes them and the further these waves are transmitted to the inner ear.

Complete answer:-
The inner ear consists of two major types of apparatus responsible for both hearing and balancing of the body.
For the hearing of sound waves, a structure called the organ of Corti is present and for maintaining the equilibrium of the body vestibular apparatus is present.
A rounded coiled duct is present in the inner ear called a cochlear duct. The organ of Corti is present in this cochlear duct.
A transverse section of cochlea shows three compartments called scala vestibuli, scala media and scala tympani. Scala vestibuli is separated from scala media by a membrane called reissner's membrane while scala media is separated from the scala tympani by a membrane called basilar's membrane.
The organ of Corti is present on the basilar membrane. It contains several sensory hair cells. These hair cells have stereocilia and kinocilia present on them that rubs against a membrane over them called a tectorial membrane.
Vestibular apparatus is responsible for the balancing of the body. It is made up of three semicircular canals, saccule and utricle. These canals have a swelling on their base called the ampulla. The characteristic bag-like structures present in the vestibular apparatus is called the macula. It is responsible for the dynamic balance of the body.

Thus the correct answer is option (B), Macula of the utricle.

Note:- When the sound waves enter the inner ear, the fluid present in the cochlear duct (endolymph) starts vibrating. This vibration leads to vibration of the organ of Corti. The hairs cells present on the organ of Corti also start vibrating and ultimately vibration of the tectorial membrane takes place. This vibration will lead to depolarization of hair cells and an action potential is generated which is carried by the vestibulocochlear nerve to the brain. This sound wave is heard due to the presence of an organ of Corti.