Section of the Skull Containing the Common Tendinous Ring

Description

Seen at the orbital apex, the common tendinous ring (anulus tendineus communis of Zinn) forms a dense annulus encircling the optic canal and the central part of the superior orbital fissure, where the sphenoid body and lesser wing meet the orbital cavity. Superior, inferior, medial, and lateral rectus muscles arise from this ring and course anteriorly along the orbital walls toward the sclera, while the globe sits anterior to the orbital apex within the bony orbit. A slightly oblique top-down section also exposes adjacent cranial base landmarks, including the nasal cavity anteriorly and the petrous temporal contours posterolaterally. At this location, millimeters matter: the ring establishes the boundary between intraconal and extraconal spaces and fixes the relationship of extraocular muscle origins to the optic nerve. Compression neuropathy in orbital apex syndrome and traumatic crowding after sphenoid or orbital fractures often present with combined visual loss and ophthalmoplegia because cranial nerve II runs through the optic canal and cranial nerves III, IV, VI, and V1 traverse the superior orbital fissure immediately adjacent to, or within, the annulus. Surgeons also use this anatomy when navigating endoscopic orbital apex decompression or transcranial approaches to the sphenoid and cavernous sinus region. Small neighborhood, high stakes. Use this artwork in head and neck anatomy teaching to anchor the concept of the orbital apex, the annulus of Zinn, and the rectus muscle cone in a single cross-sectional view. It also suits ophthalmology and neurosurgery texts discussing superior orbital fissure syndrome, optic canal decompression, and the surgical corridors that pass between rectus muscles and their fascial sheaths. Anatomical accuracy verified by SciePro's Medical Advisory Board.