Structures of the Orbit

by O.W.Henson, Jr., Ph.D.

University of North Carolina, Chapel Hill

Below is a list of structures of the orbit that should be known on the skull. You have already seen most of these.

a) Bones to be identified as contributing to the orbit include the frontal, zygomatic, maxillary, lacrimal, ethmoid, sphenoid and palatine. (palatine component is not important).

b) Lacrimal fossa of frontal bone (for lacrimal gland).

c) Optic canal of sphenoid bone (transmits optic nerve and ophthalmic artery and accompanying sympathetic nerves)

d) Anterior and posterior ethmoidal foramina (transmit vessels and nerves of same name).

e) Superior orbital fissure (transmits oculomotor, trochlear, frontal, lacrimal, nasociliary, abducens and sympathetic nerves along with ophthalmic vein).

f) Supraorbital notch or foramen (transmits supraorbital nerve and vessels).

g) Inferior orbital fissure (transmits infraorbital nerve and vessels; much of this fissure is covered over by fibrous connective tissue).

h) Infraorbital groove or canal and foramen (transmits infraorbital nerve and vessels)

i) Lacrimal groove (for lacrimal sac; leads into nasolacrimal canal).

j) Nasolacrimal canal (transmits nasolacrimal duct; opens into inferior nasal meatus)

k) Orbital plate of ethmoid (very thin bone; forms most of medial wall of orbit and separates ethmoid sinuses from orbit).

l) Greater wing of sphenoid (forms most of the posterior and lateral wall of orbit and lower margin of superior orbital fissure; separates orbit from middle cranial fossa).

m) Orbital portion of maxillary bone (forms floor of orbit and roof of maxillary sinus; contains infraorbital canal/groove)..