n. one of the spiral canals of the *cochlea. The scala media (cochlear duct) is the central membranous canal, containing the sensory apparatus of the cochlea; the scala vestibuli and scala tympani are the two bony canals of the cochlea.
n. the spiral organ of the *labyrinth of the ear, which is concerned with the reception and analysis of sound. As vibrations pass from the middle ear through the cochlea, different frequencies cause particular regions of the basilar membrane to vibrate: high notes cause vibration in the region nearest the middle ear; low notes cause vibration in the region nearest the tip of the spiral. The organ of Corti, which lies within a central triangular membrane-bound canal (scala media or cochlear duct), contains sensory hair cells attached to an overlying tectorial membrane (see illustration). When the basilar membrane vibrates the sensory cells become distorted and send nerve impulses to the brain via the *cochlear nerve. —cochlear adj.... cochlea
n. a technique for recording the electrical activity of the heart. Electrodes connected to the recording apparatus (electrocardiograph) are placed on the skin of the four limbs and chest wall; the record itself is called an *electrocardiogram (ECG). In conventional scalar electrocardiography 12 leads (see lead2) are recorded, but more may be employed in special circumstances. Intracardiac electrocardiography involves the passage of a recording catheter into the heart for accurate mapping and analysis of arrhythmias (see electrophysiological study).... electrocardiography
n. (in anatomy) an opening resembling a window. The fenestra ovalis (fenestra vestibuli) – the oval window – is the opening between the middle *ear and the vestibule of the inner ear. It is closed by a membrane to which the stapes is attached. The fenestra rotunda (fenestra cochleae) – the round window – is the opening between the scala tympani of the cochlea and the middle ear. Sound vibrations leave the cochlea through the fenestra rotunda which, like the fenestra ovalis, is closed by a membrane.... fenestra
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