Diagram of right orbit that shows the relationship of entering nerves and vessels to the annulus of Zinn.
The four recti muscles arise from a short funnel-shaped tendinous ring called the annulus of Zinn which encloses the optic foramen and a part of the medial end of the superior orbital fissure. There are 2 tendons.
The Lower Tendon (of Zinn) is attached to the inferior root of the lesser wing of the sphenoid between the optic foramen and the superior orbital fissure. The lower tendon gives origin to part of the medial and lateral recti and all of the inferior rectus. The Upper Tendon (of Lockwood) arises from the body of the sphenoid, and gives origin to part of the medial and lateral recti and all of the superior rectus muscle. The superior and medial recti muscles are much more closely attached to the dural sheath of the optic nerve. This fact may be responsible for the characteristic pain which accompanies extreme eye movements in retro-bulbar neuritis.
