Quick Facts
The spiral limbus is the thickened periosteum of the osseous spiral lamina at the attachment of the vestibular membrane (Dorland, 2011).
Structure and/or Key Feature(s)
The spiral limbus is a thickened layer of periosteum that is found on the uppermost layer of the osseous spiral lamina. The spiral limbus contains a C-shaped concavity known as the internal spiral sulcus. The upper extremity of the “C” is known as the vestibular lip and hangs over the concavity. The lower lip of the concavity is called the tympanic lip. From this endpoint, the tectorial membrane extends across the cochlear duct. The tympanic lip also allows for passage of cochlear nerve filaments via small canals known as the habenula perforata.
Function
In the lower aspect of the spiral limbus, the tympanic labia, cochlear nerve fibers are given passage to communicate with the specialized hair cells in the spiral organ (of Corti). This passage is called the habenula perforata. Additionally, the spiral limbus also receives the insertion of the basilar membrane, and so, it’s involved in supporting the orientation of the basilar membrane.
References
Dorland, W. (2011) Dorland's Illustrated Medical Dictionary. 32nd edn. Philadelphia, USA: Elsevier Saunders.
