orbit /ôr″bit/ [L, orbita, wheel track] , one of a pair of bony, conical cavities in the skull that accommodate the eyeballs and associated structures, such as the eye muscles, nerves, and blood vessels. The medial walls of the orbits are approximately parallel with each other and with the middle line, but the lateral walls diverge widely. The roof of each orbit is formed by the orbital plate of the frontal bone and the small wing of the sphenoid bones. The openings that communicate with each orbit are the optic foramen, the superior and the inferior orbital fissures, the supraorbital foramen, the infraorbital canal, the anterior and posterior ethmoidal foramina, the zygomatic foramen, and the canal for the nasolacrimal duct. −orbital, adj.
