Anatomy And Physiology

Structure of the Ear



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Human ear is a complex structure which by means of linking up with the brain cells enables sound waves to be converted into comprehensible auditory stimulations.

The human ear consists of three well demarcated sections.

External ear Middle ear Inner ear

External ear or the outer ear:

The outer portion of the ear consists of the pinna, external auditory canal and the tympanic membrane.

Pinna : This is the part of the ear which is visible to the outside and is formed largely by a skin covered cartilage bone. The part is not an essential portion for the hearing but acts as a structure which focuses the sound waves towards the ear canal.

External auditory canal: Being part cartilage and part bone, it transfers the sound waves from outside towards the tympanic membrane. The lining epithelium of the canal consists of glands which secretes serumen or ear wax. The outer portion of the canal will consist of hair as well.

Tympanic membrane or ear drum: This could well be one of the most important structures of the ear as it will receive the sound waves and the vibration will initiate the propagation of the vibratory signal of a specific frequency. The membrane is a thin fibro-muscular layer which can rupture due to extreme forces.

Middle ear:

This portion of the ear is an air filled bony enclosure which harbors three bony structures that helps in oscillating the auditory signal from the tympanic membrane towards the inner ear. These three bony components are:

Malleus or the hammer : With the appearance of a hammer, this bony part touches the tympanic membrane and receives the vibration which then be transmitted to the incus.

Incus: It transmits the vibration from the malleus to the stapes.

Stapes: Being the smallest bone in the human body, the oscillation happening in the bone will generate a vibration of the fluid inside the cochlear of the inner ear through the oval window.

Apart from the three bony components, the middle ear also comprises of a canal which extends to the posterior portion of the pharynx. This canal is known as the Eustachian canal and is helpful in equaling the middle ear pressure with the outside pressure.

Inner ear:

Probably the most complex area of the ear, it facilitates the conversion of vibratory sound waves in to auditory signals that can be perceived by the brain. The entire section is enclosed in a hard bony compartment within the skull bone.

Apart from acting as the sensory organ for sounds it facilitates the sensation of balance as well.

The inner ear consist of:

Cochlear Vestibule Semi circular canals 8th cranial nerve

Cochlear is the component responsible for sensing the sound and appears like the shell of a snail. It's filled with fluid and contains sensory receptor cells that will transmit the signal to the brain using the sensory portion of the 8th cranial nerve.

Vestibule and the semi circular canals are mainly focused on maintaining balance of the individual and in derangements could result from dizziness and vertigo kind of symptoms.

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