Cochlear duct
The cochlear duct, also called the scala media, is a triangular-shaped, centrally positioned, membranous spiral tube within the bony labyrinth of the cochlea. It is attached to the lamina of the modiolus, a thin extension of the central bony core (modiolus) of the cochlea, and to the peripheral wall of the cochlea via a thickened periosteum called the spiral ligament.
The cochlear duct divides the cochlea into two perilymph filled canals: an upper scala vestibuli (vestibular duct), and a lower scala tympani (tympanic duct). Its roof is formed by the vestibular membrane and its floor by the basilar membrane. These membranes separate the endolymph in the cochlear duct from the perilymph in the scala vestibuli and the scala tympani.
The spiral organ, the organ of hearing, sits on the basilar membrane and projects into the cochlear duct. It is composed of hair cells which extend their stereocilia into an overlying gelatinous tectorial membrane. Movement of the basilar membrane induced by pressure waves in the perilymph result in distortion of stereocilia and stimulation of the cochlear branch of vestibulocochlear nerve (CN VIII).
Terminology |
English: Cochlear duct Synonym: Scala media, cochlear labyrinth Latin: Ductus cochlearis |
Definition | Membranous spiral tube that runs within the bony cochlea |
Function | Conversion sound waves into electrical signals via the spiral organ |
Learn more about the cochlea duct of the anatomy of the inner ear in the following study unit:
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