Download How Do We Hear


Hearing is one of the five senses.

It is a complex process of picking up
sound and attaching meaning to it.

The ability to hear is critical to
understanding the world around us.

The human ear is a fully developed part
of our bodies at birth and responds to
sounds, that are very faint as well as
sounds that are very loud.

Even before birth, infants respond to
sound.

So, how do we hear?
Parts of the ear
 Outer
ear
 Middle
ear
 Inner
ear
Three parts of the ear

The ear is made up of three
primary parts: the outer ear,
middle ear and inner ear.

Each section is composed
of structures that play
distinct roles in the process
of converting sound waves
into signals that go to the
brain
Outer ear

The outer ear is composed of the visible
part of the ear (pinna), the ear canal and
the eardrum.

The cup-shaped pinna gathers sound
waves from the environment and
directs them into the ear canal

When a sound wave strikes, the
eardrum vibrates.
Aurical
Aurical is the part we see outside
 It is cone shaped and attached either
side, at about 30 to 40 degree
 The deep portion in the center is
called Concha
 There is no bone in the auricles.
 It has blood and nerve supply.

External Auditory Canal
It is an S shaped tube open at the
pinna and closed at the ear drum.
 It measures about 25-40mm.
 The outer portion of the canal has
hairs on the skin.
 It also has Wax-Secreting
glands .
 Ear canal also has blood and nerve
supply

Middle Ear

The middle ear
consists of the
smallest bones in
your body and Ear
Drum.
 Malleus
 Incus
 Stapes

The middle ear is an air-filled cavity that
holds a chain of three bones: the
hammer, anvil and stirrup.

The middle ear is connected to the back
of your nose and upper part of your
throat by a narrow channel called the
auditory tube.

The tube opens and closes at the throatend to refresh the air in the middle ear,.

Equal pressure on both sides of the
eardrum is important for normal vibration
of the eardrum.
Bones of the middle ear

The middle ear contains three tiny bones,
including the:

Hammer (malleus),
which is attached to
eardrum.

Anvil (incus), which is in the middle of the
chain of bones.
Stirrup (stapes), which
is attached to the oval
window, the membranecovered opening to the
inner ear.


It is the smallest bone Its wt is2.5mg

The vibration of the eardrum triggers a
chain of vibrations through the bones.

Because of differences in the size, shape
and position of the three bones, the force
of the vibration increases by the time it
reaches the inner ear.

This increase in force is necessary to
transfer the energy of the sound wave to
the fluid of the inner ear.
Inner ear


The inner ear contains a group of
interconnected, fluid-filled chambers.
The snail-shaped
chamber, called the
cochlea plays a role
in hearing.

Sound vibrations from the bones of the
middle ear are transferred to the fluids of
the cochlea.

Tiny sensors (hair cells) line in the
cochlea convert the vibrations into
electrical impulses that are transmitted
along the auditory nerve to your brain.

The other fluid-filled chambers of the inner
ear include three tubes called the
semicircular canals (vestibular labyrinth).

Hair cells in the semicircular canals detect
the motion of the fluids when you move in
any direction.

They convert the motion into electrical
signals that are transmitted along the
vestibular nerve to the brain.

This sensory information enables you to
maintain your sense of balance.
Traveling to the brain


Electrical impulses travel along the auditory
nerve and pass through several
information-processing centers.
Signals from the right
ear travel to the Auditory
Cortex located in the
temporal lobe on the
left side of the brain.

Signals from the left ear travel to the right
auditory cortex.

The auditory cortex, process, interpret and file
information about the sound.

The comparison and analysis of the all the
signals that reach the brain enable you to
detect certain sounds and suppress other
sounds as background noise.
SO THAT’S HOW WE HEAR!!!
Any quesions or comments?