Tendinous ring

The tendinous ring, also known as the annulus of Zinn, is the common origin of the four rectus muscles (extraocular muscles).

The tendinous ring straddles the lower, medial part of the superior orbital fissure. It attaches to a tubercle on the greater wing of the sphenoid bone (at the margin of the superior orbital fissure). Through it (from superior to inferior) pass:

  1. superior division of the oculomotor nerve (CN III)
  2. nasociliary nerve (a branch of the ophthalmic nerve)
  3. inferior division of the oculomotor nerve (CN III)
  4. abducens nerve (CN VI)

The medial portion of the ring also encompasses the optic foramen through which the optic nerve and ophthalmic artery pass.

A memory aid for the specific nerves in the structure is the mnemonic for the contents of the annulus of Zinn.

Anatomy: Head and neck

Anatomy: Head and neck

Article information

rID: 2155
System: Head & Neck
Section: Anatomy
Tag: eye
Synonyms or Alternate Spellings:
  • Tendinous ring of the eye
  • Annulus of Zinn
  • Common tendinous ring

ADVERTISEMENT: Supporters see fewer/no ads

Cases and figures

  • Figure 1: orbital apex diagram
    Drag here to reorder.
  • Updating… Please wait.

     Unable to process the form. Check for errors and try again.

     Thank you for updating your details.