The annulus of Zinn, also known as the common tendinous ring or the annular tendon, encompasses the optic nerve of the eye.
Located just below the superior oblique muscle, which travels from the top of the nose to the top of the eyeball, this oval band of fibrous tissue is the junction point of a group of muscles referred to as extraocular muscles — the four muscles that allow the human eyeball to move freely in the orbit (eye socket).
The rectus muscles (part of the extraocular muscles) originate at the annulus of Zinn, which is divided into the superior tendon of Lockwood and the inferior tendon of Zinn. Three other nerves and one artery extend through the common tendinous ring. The three nerves are: the nasocilliary nerve, which branches from the optic nerve, the abducens or sixth cranial nerve, and the oculomotor or third cranial nerve. The one artery that passes through the ring, the opthalmic artery, supplies the eye with the necessary blood supply.