How we Hear?

Structure of Ear

The ear is broken down into 3 parts:

1. Outer ear

2. Middle ear

3. Inner ear

The outer ear collects the sound waves.

The middle ear conveys the sound to the inner year.

The inner ear interprets vibrations to perceive balance and sound.

Outer Ear

It is made up of two parts, pinna and ear canal.

Pinna is like a flap like cartilaginous structure situated outside the head.

It collects sound waves and focuses them on the ear drum.

The ear canal, also called the auditory canal conveys sound waves to the eardrum.

Eardrum is also known as tympanic membrane. It separates the outer ear from the middle ear.

The tympanic membrane is a circular membrane that vibrates when sound waves strike it and transmits them to the middle ear.

Middle Ear

The middle ear contains a chain of 3 small bones, collectively called the ossicles and the eustachian tube.

The ear ossicles are three small bones:

They are named in such a way because they resemble these objects.

The malles is connected to the eardrum and the stirrup is connected to the inner ear.

These are the smallest bones in the human body.

The eustachian tube connects the middle ear to the pharynx.

It helps to equalize air pressure between the middle ear and atmosphere.

The reason there are bones in the ears and not cartilages is sound travels better in solids.

Inner Ear

The inner ear is also called the membranous labyrinth.

It is set in a very dense bone called the bony labyrinth.

It comprises of the cochlea and semicircular canals.

The cochlea is a spiral shaped fluid filled bony tube.

It contains sensory receptors for perceiving sound.

There are three semicircular canals which are placed at right angles to each other in different planes.

This gives us an understanding in all three dimensions.

One end of each canal is swollen to form an ampulla.

The canals are filled with fluid and contains sensory neurons connected to the auditory nerve.

The semicircular canals are responsible for perceiving balance of the body, when body is in motion.

The static balance is perceived by the utriculus and sacculus.

These are sac-like structures present in the short stem which joins the cochlea with the semicircular canals.