Diseases of the Ear & Mastoid Process...

The ear is the main organ of the auditory system, which is part of the sensory system for the sense of hearing.

The ear consists of the :

Outer ear

The folds of cartilage surrounding the ear canal are called the pinna. Sound waves are reflected and attenuated when they hit the pinna, and these changes provide additional information that will help the brain determine the direction from which the sounds came.

The sound waves enter the auditory canal, a deceptively simple tube. The ear canal amplifies sounds that are between 3 and 12 kHz. At the far end of the ear canal is the eardrum (or tympanic membrane), which marks the beginning of the middle ear;

Middle ear

Sound waves traveling through the ear canal will hit the tympanum, or eardrum. This wave information travels across the air-filled middle ear cavity via a series of delicate bones: the malleus (hammer), incus (anvil) and stapes (stirrup). These ossicles act as a lever and a teletype, converting the lower-pressure eardrum sound vibrations into higher-pressure sound vibrations at another, smaller membrane called the oval (or elliptical) window. Higher pressure is necessary because the inner ear beyond the oval window contains liquid rather than air. The sound is not amplified uniformly across the ossicular chain. The auditory reflex of the middle ear muscles helps protect the inner ear from damage. The middle ear still contains the sound information in wave form; it is converted to nerve impulses in the cochlea; and

Inner ear

The inner ear consists of the cochlea and several non-auditory structures. The cochlea has three fluid-filled sections, and supports a fluid wave driven by pressure across the basilar membrane separating two of the sections. Strikingly, one section, called the cochlear duct or scala media, contains an extracellular fluid similar in composition to endolymph, which is usually found inside of cells. The organ of Corti is located at this duct, and transforms mechanical waves to electric signals in neurons.

The following is a list of some common ear disorders:

• Otitis externa;

• Abscess of external ear;

• Malignant otitis externa;

• Perichondritis of external ear;

• Impacted cerumen;

• Collapse of external ear canal;

• Swimmer's ear; etc.

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OTITIS MEDIA

A comprehensive list of diseases of the ear and mastoid process may be found at ICD-10 Chapter 8 Block H60-H95. ~