Annulus of Zinn

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Annulus of Zinn
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
Latin annulus tendineus communis
Gray's subject #227 1022
Dorlands/Elsevier a_50/12143789

The annulus of Zinn, also known as the annular tendon, circle of Zinn-Haller 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 older sources (such as Gray's Anatomy) distinguish between these terms more precisely, with the annulus tendineus communis being the parent structure, divided into two parts:

It should not be confused with the Zonule of Zinn, though it is named after the same person (Johann Gottfried Zinn).

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