The osseous spiral lamina is a bony shelf or ledge which projects from the
modiolus into the interior of the canal, and, like the canal, takes two-and-three-quarter turns around the modiolus.
It reaches about half-way toward the outer wall of the tube, and partially divides its cavity into two passages or scalae, of which the upper is named the
scala vestibuli
The vestibular duct or scala vestibuli is a perilymph-filled cavity inside the cochlea of the inner ear that conducts sound vibrations to the cochlear duct.
It is separated from the cochlear duct by Reissner's membrane and extends from the vesti ...
, while the lower is termed the
scala tympani
The tympanic duct or scala tympani is one of the perilymph-filled cavities in the inner ear of humans. It is separated from the cochlear duct by the basilar membrane, and it extends from the round window to the helicotrema, where it continues as ...
.
Near the summit of the
cochlea
The cochlea is the part of the inner ear involved in hearing. It is a spiral-shaped cavity in the bony labyrinth, in humans making 2.75 turns around its axis, the modiolus. A core component of the cochlea is the Organ of Corti, the sensory or ...
the lamina ends in a hook-shaped process, the
hamulus laminae spiralis; this assists in forming the boundary of a small opening, the
helicotrema
The helicotrema (from el, ἕλιξ elixmeaning coil and rēmameaning hole) is the part of the cochlear labyrinth where the scala tympani and the scala vestibuli meet. It is the main component of the cochlear apex. The hair cells near this ...
, through which the two
scalae communicate with each other.
From the spiral canal of the modiolus numerous canals pass outward through the osseous spiral lamina as far as its free edge.
In the lower part of the first turn a second bony lamina, the ''
secondary spiral lamina'', projects inward from the outer wall of the bony tube; it does not, however, reach the primary osseous spiral lamina, so that if viewed from the vestibule a narrow fissure, the
vestibule fissure, is seen between them.
See also
*
Basilar membrane
The basilar membrane is a stiff structural element within the cochlea of the inner ear which separates two liquid-filled tubes that run along the coil of the cochlea, the scala media and the scala tympani. The basilar membrane moves up and down ...
References
Bones of the head and neck
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