Annulus of Zinn | |
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Rectus muscles: 2 = superior, 3 = inferior, 4 = medial, 5 = lateral Oblique muscles: 6 = superior, 8 = inferior Other muscle: 9 = levator palpebrae superioris Other structures: 1 = Annulus of Zinn, 7 = Trochlea, 10 = Superior tarsus, 11 = Sclera, 12 = Optic nerve |
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Anterior view | |
Latin | annulus tendineus communis |
Gray's | subject #227 1022 |
The annulus of Zinn, also known as the annular tendon or common tendinous ring, is a ring of fibrous tissue surrounding the optic nerve at its entrance at the apex of the orbit. It is the origin for five of the six extraocular muscles. (Some sources only include four.[1])
It can be used to divide the regions of the superior orbital fissure.[2]
The arteries surrounding the optic nerve are sometimes called the "circle of Zinn-Haller" ("CZH").[3] This vascular structure is also sometimes called "circle of Zinn".
Some sources distinguish between these terms more precisely, with the annulus tendineus communis being the parent structure, divided into two parts: [4]
It is named for Johann Gottfried Zinn.[5][6] It should not be confused with the Zonule of Zinn, though it is named after the same person.