It consists of the auricle and external acoustic meatus (or ear canal). The external ear, like the middle ear, serves only to conduct sound to the inner ear. This mixture of bones, nerves, vessels, membranes, and muscles that make up the ear will be described in this article. Cochlear duct provides hearing informationĪuricular hematoma, otitis (externa, media, interna), blockage of the pharyngotympanic (Eustachian) tube, high tone deafness Semicircular ducts provide information about movements of the head Utricle and saccule provide information about the position of the head
Bony labyrinth supports its membranous counterparts Parts: bony labyrinth (vestibule, semicircular canals, cochlea) and membranous labyrinth (utricle, saccule, semicircular ducts, cochlear duct) Parts: tympanic cavity, auditory ossicles, muscles of the ossiclesįunction: transforming a high-amplitude low-force sound wave into a low-amplitude high-force vibration and transmitting it to the internal ear Parts: auricle, external acoustic meatus, tympanic membraneįunction: capture and conduction of sound The ear is anatomically divided into three portions: The main functions of the ear are, of course, hearing, as well as constantly maintaining balance. It is situated bilaterally on the human skull, at the same level as the nose. The ear is a complex part of an even more complex sensory system. 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.External auditory meatus, External acoustic pore 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).