The cochlea: auditory sense. The cochlea: auditory sense

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Daisy Small
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1 Inner ear apparatus 1- Vestibule macula and sacculus sensing acceleration of the head and direction of gravity 2- Semicircular canals mainly for sensing direction of rotation of the head 1 3- cochlea in shape and resembles the shape of some common snail-shells. 2

2 Cranial nerve VIII sensory axons carrying impulses from all three structures correct name is the Vestibulocochlear nerve Aka, auditory nerve. 3 The series of events in sound reception (a) Sound vibrations in the environment cause vibrations of the tympanic, separates the external auditory canal from the middle ear cavity. 4

3 Middle ear ossicles Series of 3 tiny interconnected s: Extending across the middle ear cavity (air filled) from the surface of the tympanic to the surface of the oval window separating the middle ear from the ear) a Vibrations of the tympanic cause vibrations of the middle ear ossicles, resulting in vibrations of the oval window. 5 Inner ear cavity is filled with a lymph-like (CSF-like) liquid; vibration of the oval window Vibrates the basilar of the cochlea Vibrates the round window separating the ear cavity from the middle ear cavity. 6

4 Except at the round window and oval window the ear is entirely encased in compact tissue. Basilar divides the cochlea into upper and lower parts; full length of the cochlea Oval window bulges into the upper portion, causing the basilar to bulge downward; then pushes the round window outward. 7 Organ Middle portion of the basilar, part of the actual auditory sense-organ of the cochlea In addition it includes the tectorial. 8

5 Phalangeal. Inner, one wide, running the length of the cochlea Outer, three wide. hair hair tectorial basilar 9 Inner and hair On each of these is a hair : the actual sensory. The hair have cilia or microvilli which extend to the underside of the tectorial. They are called stereocilia. hair hair tectorial basilar 10

6 Support-bridge Table-like structure runs the length of the cochlea relatively stiff, fibrous protein material non-ular but has associated with it can be referred to as the "support-bridge"; it is eosinophilic. hair hair tectorial basilar 11 Pillar Thin table-top-like portion of the support-bridge is supported above the main, lower part of the basilar by two s A strip of, one thick, lies against the surface of each ; these are called hair hair tectorial basilar 12

7 Internal.; Between the proximal part of the tectorial and the basilar Tectorial ; is non-ular and composed of eosinophilic protein; it is gelatinous; the stereocilia are in its lower surface hair hair tectorial basilar 13 Other structures of the cochlea. ; thin ular ; divides the space above the basilar into two chambers scala vestibuli : Above the ; contains lymph-like liquid called perilymph. scala media: Below the ; filled with endolymph. hair hair tectorial basilar 14

8 Stria vascularis. Edge of the scala media; against a highly vascularized layer of the cochlear wall ; produces endolymph by leakage and active transport from its caies. hair hair tectorial basilar 15 Spiral ganglion is adjacent to the region where the basilar joins the wall of the cochlea. Contains the somas of the bipolar sensory neurons; dendrites have their endings on the hair Axons of these neurons compose most of cranial nerve VIII These axons end on the auditory (cochlear) nucleus of the anterior part of the medulla of the brain. hair hair tectorial basilar 16

9 scala tympani. Chamber below the basilar ; continuous with the scala vestibuli at the distal, end of the cochlea; filled with perilymph. hair hair tectorial basilar 17 Organ Cells of Cells of Outer Outer hair Inner hair Tectorial Inner sulcus Vestibular Spiral ligament Internal Limbus is Bone Basilar Outer Outer Inner Inner Inner Cochlear nerve fibers Scala Tympani Rao

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Ear. Utricle & saccule in the vestibule Connected to each other and to the endolymphatic sac by a utriculosaccular duct

Ear. Utricle & saccule in the vestibule Connected to each other and to the endolymphatic sac by a utriculosaccular duct Rahaf Jreisat *You don t have to go back to the slides. Ear Inner Ear Membranous Labyrinth It is a reflection of bony labyrinth but inside. Membranous labyrinth = set of membranous tubes containing sensory