Auditory canal function registration#

Lined by thin keratinized stratified squamous epithelium along the entire canal also covers the external tympanic membrane.

The outer third is formed by cartilage, the inner two thirds are formed by bone.

External auditory meatus (auditory canal).

Function: collects sound waves important for directional hearing.

Definition: the external portion of the ear.

It transmits information to the brain via the vestibular nerve.

Auditory canal function registration#

The organ of Corti is responsible for sound detection, and it transmits auditory information to the brain via the cochlear nerve, while the vestibular system is responsible for the registration of body movement and spatial orientation. The inner ear is a fluid-filled cavity that contains the organ of Corti and the vestibular system. The ossicles amplify the resulting vibrations and transmit them to the inner ear via the oval window. The auricle captures sound waves and directs them through the external auditory canal towards the tympanic membrane, thus setting it in motion. The eustachian tube connects the middle ear to the nasopharynx, equalizing the pressure between the middle ear and the atmosphere. The middle ear is a hollow structure that comprises the tympanic cavity, the ossicles, and the eustachian tube. The outer ear comprises the auricle ( pinna), external auditory meatus (auditory canal), and tympanic membrane ( eardrum), which separates the outer ear from the middle ear. It is divided into three sections: the outer, the middle, and the inner ear. Both from an intact tympanic membrane and providing an air cushion which prevents aspiration from nasopharynx (the back of the nose).Įssential to the proper working of the middle ear is the function of the Eustachian tube, a tube connecting the middle ear to the nasopharynx.The ear is the organ of hearing and balance. The resonant frequency is when mass reactance and elastic reactance are equal. Transmission through the incudo-stapedial joint is more efficient at lower frequencies. A peak resonance at 3 kHz leads to a 5- to 6-dB decrease in sound transmission at that frequency. A final modification is imparted by the resonance of the mastoid air cells. Gain decreases by 8 to 9 dB per octave above 1 kHz. Below 1 kHz the gain averages 23 dB and is relatively flat with a peak of 26 to 27 dB at 0.9 kHz. An overall 20- to 30-dB sound pressure gain is thus produced by the impedance matching function of the middle ear: sound energy gain transferred by the middle ear is frequency dependent.

These unique characteristics of the tympanic membrane also protect the inner ear from static pressure variations while remaining sensitive to small pressure changes. Both the outward convexity of the eardrum and radial orientation of collagen fibres in the tympanic membrane lead to a twofold amplification of sound pressure onto the umbo. A smaller contribution is made by the catenary lever. The ossicular lever results from the long axis of the malleus being 1.3 times the length of the long process of the incus.

This is thought to be the main impedance matching mechanism. The hydraulic lever concentrates acoustic energy at the oval window and results from the 17- to 20-fold difference in vibratory surface of the tympanic membrane compared with the smaller area of the stapes footplate. This occurs through three major mechanisms: a hydraulic lever, ossicular lever, and catenary lever. Impedence matching: this is transference of energy from the air of the middle ear to the inner ear fluid. The middle ear is made up of the tympanic membrane (ear drum) and the ossicles (the 3 bones of hearing). The external ear is made up of the pinna (auricle) and the external auditory canal (ear canal). Essentially the function of the ears is to receive, amplify and convert sound (a pressure wave), into a neural impulse (an electric signal) that is sent to auditory cortex (the part of the brain that processes these signals into what we actually hear).