cochlea Part of the inner ear of mammals, birds, and some reptiles that transforms sound waves into nerve impulses. In mammals it is coiled, resembling a snail shell, and is divided by membranes into three parallel canals (see illustration): the middle cochlear duct (scala media) and two outer canals – the vestibular canal (scala vestibuli) and the tympanic canal (scala tympani) – formed from one long canal folded on itself at a bend at the apex of the cochlea. The small opening at this point, where the vestibular and tympanic canals communicate, is called the helicotrema. The cochlear duct is filled with a fluid (see endolymph) and contains the organ of Corti, which houses the sound receptors. The other two canals also contain a fluid (see perilymph). Sound-induced vibrations of the oval window are transmitted through the perilymph and endolymph and stimulate hair cells in the organ of Corti. These in turn stimulate nerve cells that transmit information, via the auditory nerve, to the brain for interpretation of the sounds.

coch·le·a / ˈkōklēə; ˈkäk-/ • n. (pl. -le·ae / -lēˌē; -lēˌī/ ) the spiral cavity of the inner ear containing the organ of Corti, which produces nerve impulses in response to sound vibrations.DERIVATIVES: coch·le·ar adj.ORIGIN: mid 16th cent. (used to denote spiral objects such as a spiral staircase and an Archimedean screw): from Latin, ‘snail shell or screw,’ from Greek kokhlias. The current sense dates from the late 17th cent.

cochlea Fluid-filled structure in the inner ear. It has a shape like a coiled shell, and is lined with hair cells which move in response to incoming sound waves, stimulating nerve cells to transmit impulses to the brain. Different groups of hair cells are stimulated by different pitches of sound.

cochlea Part of the inner ear of some reptiles, birds, and mammals. It is concerned with the analysis of the pitch of received sound. In mammals other than Monotremata it is spirally coiled.

cochlea spiral cavity of the internal ear. XVII. — L. coc(h)lea snail-shell, screw — Gr. kokhlías, prob. rel. to kógkhē CONCH.