The spiral organ of Corti (organon spirale [Corti]; organ of Corti) is composed of a series of epithelial structures placed upon the inner part of the basal lamina.
The more central of these structures are two rows of rod-like bodies, the inner and outer rods or pillars of Corti. The bases of the rods are supported on the basal lamina, those of the inner row at some distance from those of the outer; the two rows incline toward each other and, coming into contact above, enclose between them and the basal lamina a triangular tunnel, the tunnel of Corti. On the inner side of the inner rods is a single row of hair cells, and on the outer side of the outer rods three or four rows of similar cells, together with certain supporting cells termed the cells of Deiters and Hensen. The free ends of the outer hair cells occupy a series of apertures in a net-like membrane, the reticular membrane, and the entire organ is covered by the tectorial membrane.