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Fact File : The ear captures sound and helps you recall that sound throughout your life. The ear helps the body respond emotionally, according to thesound heard, like emotions of love on hearing the sound of a loved one, emotions of fear on hearing a threat or a gunshot!

Majority of the human population is born with fully developed external and internal ears. Even a fetus inside its mother's womb is able to hear all thesounds that are loud.

Parts and Functions of the earThe human ear is divided into five parts. These five parts of human ear, have specific functions that help in the process of hearin .

Parts of Human EarThe parts of the human ear include:

!uter Ear

Middle Ear

"nner Ear

#coustic $erve

%entral #uditory &rocessin %enters

Outer ear is divided into the pinna and the external auditory meatus . The pinna, also nown as the auricle is the external ear part that is located andseen on each side of our head. "t is made up of cartila e and soft tissue. This helps in maintainin a particular ear shape and remains pliable. The pinna isli e a funnel that collects the sound vibrations from around us and funnels them towards the external auditory meatus.

The external auditory meatus is also called the ear canal. The e ar canal helps understand and determine the source and direction of the sound. "t is only( inch in diameter and extends from the pinna to the tympanic membrane . The tympanic membrane is commonly called the eardrum. ) in and haircover the outer ear canal foundation and the cerumen land or the wax land is present in this area. The ear canal develops into a bony structure ti htlycovered by s in, near the eardrum.

Fact File : The eardrum is an extremely sensitive organ. It can detect the sounds with an intensity range of approximately 100,000,000 to 1. hen thesoftest sound hits the eardrum, it moves about one millionth of an inch and this vibration is transferred to the inner ear for further processing within thebrain.

The middle ear is the structure that be ins at the end of the tympanic membrane . There are three tiny bones nown as t he ossicles that ma e up themiddle ear. These bones connect the eardrum to the inner ear. )ound waves funneled in throu h the pinna, hit the eardrum. This causes the eardrum tomove bac and forth, in other words, vibrate, causin the ossicles to move. This causes the sound waves to convert into mechanical vibration.

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The three tiny bones formin the ossicles are malleus , incus and stapes . The malleus also nown as the hammer is connected to the eardrum on one sideand the incus , nown as the anvil on the other side. The anvil is connected to the third bone stapes , also called the stirrup. The sound waves convertedinto mechanical ener y are transferred throu h this ossicular chain. There is an in and out movement at the stirrup base nown as the stapes footplate ,that matches the incomin sound waves. The be innin of the inner ear is mar ed by the oval window that fits in the stapes footplate.

The middle ear is present in the mastoid section of the temporal bone . The temporal bone is the s ull bone that is present on each side of the head that isfilled with air. The "ustachian tube runs from the middle ear front wall to the bac of the nose and nasopharynx , that is, throat. The function of the eartube that is the Eustachian tube is, to provide ventilation and access to the external air and balance the air pressure on the both sides of the eardrum.

Fact File : hen there is a change in air pressure in our ears, we can chew, swallow and even yawn.

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The inner ear houses the sensory or ans that help in hearin and maintainin balance. The part of human ear involved in the function of hearin is thecochlea . #nother major function of the human ear is to maintain balance of the body. The different parts of the human ear that help in balancin are thesemicircular canals consistin of the utricle and the saccule present in the inner ear.

The bony structure that is shaped li e a snail and filled with endolymph and perilymph fluid is called the cochlea. The sensory receptor called the #rgan of $orti is present inside the cochlea. "t has hair cells and nerve receptors, re*uired for hearin .

The middle ear movement pushes the mechanical ener y in the oval window inside the cochlea. The tiny hair cells are stimulated due to the force thatmoves the fluids inside the cochlea. %itches or the specific sound fre*uencies stimulate specific individual hair cells in the inner ear. Thus, certainfre*uencies are responded by certain hair cells. The hair cells translate si nals into nerve impulses. The cochlear portion of the +""" cranial nerve, theacoustic nerve , transmits the nerve impulses to the brain.

The acoustic nerve is the part of human ear that transmits impulses from the cochlea to the mid brain re ion, the cochlear nucleus , and further on toother pathways in the brain, that end in the auditory cortex of the brain. The nerve fibers of each ear are divided into two pathways from the cochlearnucleus. !f these two pathways, one ascends towards the auditory cortex in one hemisphere of the brain and the other crosses over and ascends to theother hemisphere of the brain. Thus, the function of the human ear nerve fibers pathway is to transmit data or information received from both ears toboth the hemispheres of the brain.

The central auditory system function of human ear is to process auditory information carried to the brain. The central auditory system plays a role inthe followin functions of human ear:

The locali ation and laterali ation of the sound

-ifferentiatin between the different sounds

Temporal resolution, mas in , inte ration and orderin

educin the auditory performance when there are competin acoustic si nals

educin the auditory performance when there is a presence of de raded acoustic si nal

Functions of the Ear/e have understood the different parts of a human ear and ot an overview of their functions. $ow, let us have a l oo at the functions of the ear, in alittle detail.

The pinna and the ear canal deliver the sound waves to the middle ear. Forei n bodies li e insects, dust, etc. areprevented from ainin entry into the ear due to the presence of wax and hair in this re ion. This helps inpreventin many ear infections.

The eardrum vibrates accordin to the fre*uency and the amplitude of sounds that stri e it.

The middle ear function of human ear is to transmit and amplify the sounds vibrated from the eardrum towardsthe oval window. "t also acts as a dampener to loud sounds that may dama e the cochlea.

The round window is a flexible membrane present at the opposite end of the fluid filled channels from the ovalwindow. The round window function of human ear is to eep the cochlear fluids contained within the scala vestibuliand scala tympani. "t also functions as a multiplier of the sound waves enerated from the oval windowmembrane.

The malleus transmits sound vibrations from the eardrums to the incus.

The incus transmits the sound vibrations to the stapes.

The stapes transmit the vibrations to the membrane of the inner ear present inside the fenestra ovalis .

The semicircular canals function is to maintain the balance by respondin to ravity and the accelerationchan es of the head.

The mastoid bone acts as an amplifier of certain sounds that are in the low0fre*uency ran e.

The cochlea , the actual or an that helps in hearin functions as a sound wave interpreter and converter.

Parts and Functions of the Ear Involved in BalancingThe sense of e*uilibrium is controlled by the vestibular system. T his system is present in the inner e ar. The temporal bone space is shared between thevestibular and the cochlea. The fluids present in the cochlea are present in the vestibular. "n order to maintain balance and e*uilibrium when standin ,sittin , runnin , wal in etc. in relation to ravity without fallin over, is ta en care by the vestibular system. Many other systems li e vision, muscleresponse, help the vestibular system in performin its balancin function of human ear effectively.

The utricle and the saccule of the semicircular canals lie in anatomically different planes. These planes lie at a ri ht an le to each other. These planeseach have a specific function that deals with movement, that is, up and down, side to side and tiltin from one side to the other side. The se canals

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contain sensory hair cells and are activated by the movement of the endolymph fluid. /hen the head tilts to one side, the sensory hair cells send a nerveimpulse to the brain with the help of acoustic nerve. The fluid in the semicircular canal acts on calcium carbonate crystals 1%a%! 23. These crystals shift ontheir sensory hair beds at the base of the utriculus and the sacculus. These impulses are stimulated by the crystals present and are processed in the brainstem and the cerebellum area, in relation to the position of head with ravity.

Fact File : hen the calcium carbonate crystals break off from their hair beds, they float within the vestibular labyrinth. These floating crystals causeserious balance and vertigo problems.

How the Human Ear Functions

/e have seen the parts of human ear and the functions of the ear. 4ut, if you want to understand how the human ear functions, the followin dia ram ofthe ear will prove to be useful. 5ou can see in the dia ram that the external ear captures the travelin sound waves. The sound waves enter throu h thepinna into the ear canal. Throu h the ear canal the sound waves reach the eardrum. These sound waves cause vibrations of the eardrum that are passedon to the middle ear. The three tiny bones in the middle ear pass the vibrations over to the inner ear. The stapes deliver the sound waves to the cochleathrou h the round window of the outer part of the inner ear, called the bony labyrinth. These vibrations cause the perilymph fluid present in the cochleato vibrate. These vibrations are pic ed up by the sensory hair cells, which translate it into nerve impulses and deliver it to the auditory nerve present atthe base of cochlea. The +""" cranial nerve carries the messa es to the brain, where it is read and translated into meanin ful sounds.

&ketched 'y (bhishake &harma

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