Functions of middle ear muscles
Written by D C MorganFunctions of middle ear muscles: The basic function of the intratympanic muscles, the stapedius and tensor tympani is to protect the inner ear from the damage due to high intensity sounds. Loud sounds reflexly stimulate the mus-cles, which cause stiffness, of the ossicular chain and thus less of sound is passed into inner ear. As […]
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Ear: Bone conduction of sounds
Written by D C MorganBesides air conduction, the sounds are also transmitted through bone which may be due to vibration of skull by the subject’s own sound waves, the free-field sound energy or by application of the vibrating body directly to skull.
The stimulation of the sense organ by the bone conducted sounds occurs as a result of compressional mechanism […]
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Functions of eustachian tube
Written by D C MorganFunctions of eustachian tube: Eustachian tube helps in aeration of middle ear. Normally aer-ated middle ear cavity is essential for proper functioning of tym-panic membrane and ossicles and provides a hypotympanic air bubble for movement of the round window membrane.
Eustachian tube helps in equalization of pressure in middle ear. The atmospheric pressure decreases, as during […]
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Impedance matchingof middle ear
Written by D C MorganImpedance matchingof middle ear: Transmission of sound from middle ear containing air to the cochlea containing fluid (Fig. 2.11) would have been difficult as this ence in the acoustic properties of the two media, most of the sound would be relfecte ac (impeded) an this would mean a oss o about 99.9% of acoustic energy. […]
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PHYSIOLOGY OF HEARING
Written by D C MorganSound is conducted from the external auditory canal through the tympanic membrane and ossicles to cochlea which is sensory organ of hearing. The impulses pass from inner ear through the nerves to central connections and auditory cortex in brain, whero message is perceived.
The hearing mechanism thus involves two components:
(i) The sound conducting mechanism (transmission).
(ii) The perceptive neural […]
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The membranous semicircular ducts
Written by D C MorganThe membranous semicircular ducts
These open into the utricle by five openings. One end of the each duct near the utricle is dilated and is called. ampulla which houses the vestibular receptor organ. The vestibulF,r receptor organ is a specialized neuroepithelium called crista. Thc sensory cells have cilia, which project into gelatinous substance probably secreted by […]
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Saccule and utricle
Written by D C MorganSaccule and utricle
The utricle lies in the upper part of the vestibule while the saccule lies below and in front of utricle. The ducts from the saccule and utricle join to form the endolymphatic duct which occupies the bony aqueduct of the vestibule.
The saccule is also connected by a small duct called ductus reuniens […]
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Membranous labyrinth
Written by D C MorganMembranous labyrinth
It is filled with endolymph and comprises of:
(i) The saccule and utricle.
(ii) The membranous semicircular ducts within the corresponding bony canals.
(iii) The ductus cochlearis in the bony cochlea.
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The ductus cochlearis (scala media)
Written by D C MorganThe ductus cochlearis (scala media)
The membranous duct of the cochlea lies in bony canal of coch-lea. It is roughly triangular, with base formed by basilar membrane.. The basilar membrane stretches, from osseous spiral lamina to spiral ligament, which is a thickened endosteum on the outer wall of the bony canal. Continuous with spiral ligament are […]
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The bony cochlea
Written by D C MorganThe bony cochlea lies in front of the vestibule and is like a snail shell. It has 23/4 truns, coiling around a central bony axis called modiolus, osseous spiral lamina, extends lateraly from the modiolus and winds spirally around it.
In the attached margin of this spiral lamina is the spiral canal of the modiolus.
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Vestibule
Written by D C MorganVestibule is the central part of labyrinth. On its lateral surface is the opening of the oval window, which is closed by the foot plate of the stapes. On the posteror portion of the medial wall of the vestibule is an opening for aqueduct of the vestibule.
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Semicircular canals
Written by D C MorganSemicircular canals
These are three in number. The superior canal lying transverse to the long axis of the petrous part, forms arcuate eminence on the anterior surface of the petrosa. The posterior semicircular canal lies in a plane parallel to the posterior surface of the petrous. The lateral canal lies in an angle between the superior […]
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ENT: Facial recess
Written by Dr.ChrisFacial recess is bounded laterally by the deep aspect of the pos¬tero superior part of the tympanic annulus, superiorly by the short process of incus and medially by the facial nerve which separates this recess from sinus tympani.
Facial recess is explored during posterior tympanotomy procedure.
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Development of the external and middle ear
Written by Dr.ChrisDevelopment of the external and middle ear : The structures of outer and middle ear deyelop from the branches
The pinna: During 6th week of intrauterine life, the six tubercles appear on the first and second branchial arches around the ~rirssf branchial groove. The tubercles fuse to ether to for e pima. External auditory meatus and […]
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Development of the Ear
Written by Dr.ChrisDevelopment of the Ear: The knowledge of the development of the ear is important for the diagnosis and the therapy of the various diseases of the ear. It is also quite necessary to know the various anatomical variations that the surgeon may encounter on the table.
The two functional parts of the auditory mechanism have two […]
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