Sound reaches the brain through the ear and we get
to her. But the process of hearing is more complex than this statement. The ear
can be divided into four major sections according to the function each of them
plays in the furthering the process of hearing.
hearing process center in the brain
All these four sections need to work in tandem in
order to direct the external sounds happening outside the head and enable them
to reach the brain
which effectively processes it to make us ‘hear’. Given below is a brief
description of the anatomy of the ear and how the parts help in hearing.
The external ear is divided into two parts:
– This is the outer portion that is visible on both sides of the head.
auditory meatus – This is the ear canal that begins from the pinna and
joins the tympanic membrane which is commonly known as the eardrum.
The pinna is built with skin and
cartilage supported by some muscular attachments to the back of the head. Pinna
acts as a funnel in collecting and directing the sounds and helps them travel
down the ear canal. There are certain twists and folds in the pinna which
increase the frequency sounds and helps us to gauge the source and direction of
the sound source. This also helps us to focus on the source and reduces the
background noise. This further explains that if we cup our hands around our
ears, the sound gets further amplified.
The external auditory meatus is shaped as a twisting
tunnel and 2.5 cm is length and its diameter is as big as a pencil eraser. The
walls of this canal are extremely sensitive to touch because of a cranial nerve
branch passing beneath surface of the back canal wall. Two-thirds of this canal
is bordered by cartilage and houses the glands that produce ear wax or cerumen.
The inner one-third part is encased with bone.
The canal has a natural resonance feature that help in the boosting of the
The middle ear constitutes of air-filled space
between the ear drum and inner ear. It has three tiny bones called ossicles
that form the linkage along with some tiny ligaments and muscles that act as
supportive feature. They also help in adjusting the tension of the bone chain.
The tympanic membrane has a concave shape which vibrates when sound travels
down the ear canal. The ossicles transfer these vibrations to the inner ear or
first bone that is attached to the inner surface of the membrane is called
malleus or hammer
second bone is known as incus or anvil
bone or innermost bone is called stapes or stirrup.
As the footplate of the stapes vibrates, it reaches
the cochlea through an oval-shaped opening. The sound energy is now transferred
through the fluids in this section.
The middle ear space is connected to the throat by
the Eustachian tube and that is why a ‘pop’ is heard when there is a change in
the pressure balance.
There are two sections here: vestibular or the
balancing part and cochlea. The vestibular portion senses the head position
with respect gravity. The cochlea is shaped as a coiled canal encased within dense
bone tissue inside the skull. It houses three membranous canals filled with
fluid. There is a specialized group of cells called Organ of Corti which passes
the vibratory energy. This follows by a shearing action on the celia on the
upper surface of the cells. This generates an electro-chemical signal that
passes through the auditory nervous pathway to the brainstem into the temporal
lobes of the brain, and we finally get to ‘hear’.