Anulus tendineus

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
Anterior view
Details
Identifiers
Latin	Anulus tendineus communis
Dorlands /Elsevier	a_50/12143789
TA	A15.2.07.015
FMA	49071
Anatomical terminology []

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 common origin of the four rectus muscles (extraocular muscles).

It can be used to divide the regions of the superior orbital fissure.

The arteries surrounding the optic nerve are sometimes called the "circle of Zinn-Haller" ("CZH"). This vascular structure is also sometimes called "circle of Zinn".

The following structures pass through the tendinous ring (superior to inferior):

Some sources distinguish between these terms more precisely, with the anulus tendineus communis being the parent structure, divided into two parts:

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