Inner Ear Anatomy PDF

Inner Ear Anatomy Ear Anatomy 1. Outer ear 2. Middle Ear 3.Inner Ear Anatomical composition of the Inner Ear The inner ear houses the cochlea, the sensory organ for hearing. In addition, the inner ear houses the vestibular organs with its three semicircular canals and two otoliths (sa...

Inner Ear Anatomy Ear Anatomy 1. Outer ear 2. Middle Ear 3.Inner Ear Anatomical composition of the Inner Ear The inner ear houses the cochlea, the sensory organ for hearing. In addition, the inner ear houses the vestibular organs with its three semicircular canals and two otoliths (saccule and utricle). The middle ear connects to the inner ear membranous labyrinth at the footplate of the stapes in the oval window.  Key Structures:  Cochlea: A spiral-shaped of 3 fluid filled duct organ(scala vestibuli, scala tympani and scala media) responsible for converting sound waves into nerve impulses through Organ of Corti which located at the Basilar membrane of the Scala media.  Vestibule: consists of: Otolith Organ: The central part of the bony labyrinth, Utricle and saccule involved in linear acceleration. Semicircular Canals: Three looped structures, Superior, posterior and lateral that detect The co­chlea The co­chlea spirals about 2 3⁄4 turns to save space within the skull, because if uncoiled it is about 35 mm long, The height of the cochlea from base to apex is only about 5 mm. The wider part of the cochlea is called the base, and the tip of the cochlea is called the apex. The inner ear is set up like a duct inside of a duct. The outer duct is called the osseous or bony labyrinth because its walls are made of the surrounding bone. The inside duct is made of membranous materials and is thus The co­chlea High frequencies maximum displacement of basilar membrane at the base of the cochlea. Low frequencies causing longer travelling wave with maximum amplitude near the apex of the cochlea.  The co­chlea The cochlea divided into three chambers: (a)scala vestibuli (b)scala media (c)scala tympani Both scala tympani and vestibuli communicated at the helicotrema and they are filled by perilymph “low K+ and high Na+ and Ca+”, while scala media filled with endlymph “high K+ and low Na+ and Ca+”. The co­chlea The Organ of Corti is the sensory part of the cochlea, found within the scala media along the basilar membrane. The cells of the organ of Corti include:  Inner hair cells (IHCs)  Outer hair cells (OHCs) With stereocilia in the top of each, the longest one known as kinocilium. Tectorial membrane The vestibule The vestibule is the area of the bony labyrinth that lies between the cochlea and the semicircular canals. Inside the ves­tibule is where two other vestibular organs, the saccule and utricle, are located. The saccule and utricle are often referred to as the otolith organs, and respond primarily to linear accelerations of the head. Semicircular Canals The three semicircular canals are oriented in three orthog­onal planes and respond primarily to angular ac­celerations of the head. The sensory organe in this part known as