Structure/Morphology
The common tendinous ring is a ring of fibrous tissue that surrounds the optic canal and partially extends over the superior orbital fissure.
Anatomical Relations
Many structures that enter the orbit via the optic canal or superior orbital fissure come to lie within the common tendinous ring. Those that enter the optic canal include the optic nerve and ophthalmic artery. Those passing through the superior orbital fissure include the oculomotor and abducens nerves, and the nasociliary branch of the ophthalmic nerve.
Function
The common tendinous ring provides the origin site for the four recti muscles (i.e., the superior, inferior, medial, and lateral recti muscles).
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Annulus of Zinn
It is here that the annulus of Zinn, a fibrous ring surrounding the contents of the optic foramen and central aspect of the superior orbital fissure, emanates from the merging of the pia and arachnoid.
