Spiral limbus
Limbus spiralis
- Latin synonym: Limbus laminae spiralis osseae
- Synonym: Limbus of osseus spiral lamina
Definition
On the upper plate of the osseous spiral lamina which is outside the vestibular membrane, the periosteum is thickened to form the limbus laminæ spiralis, this ends externally in a concavity, the sulcus spiralis internus, which represents, on section, the form of the letter C; the upper part, formed by the overhanging extremity of the limbus, is named the vestibular lip; the lower part, prolonged and tapering, is called the tympanic lip, and is perforated by numerous foramina for the passage of the cochlear nerves.
The upper surface of the vestibular lip is intersected at right angles by a number of furrows, between which are numerous elevations; these present the appearance of teeth along the free surface and margin of the lip, and have been named by Huschke the auditory teeth.
The limbus is covered by a layer of what appears to be squamous epithelium, but the deeper parts of the cells with their contained nuclei occupy the intervals between the elevations and between the auditory teeth. This layer of epithelium is continuous on the one hand with that lining the sulcus spiralis internus, and on the other with that covering the under surface of the vestibular membrane.
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