part_8/chapter_45.htmlIndirect repeat in December 2010WALLS OF THE ORBIT:The orbit possesses four walls; a roof, lateral wall, floor, and medial wall.* The roof (frontal and sphenoid bones) presents the fossa for the lacrimal gland anterolaterally and the trochlear pit for the cartilaginous or bony pulley of the superior oblique muscle anteromedially. The optic canal lies in the posterior part of the roof, between the roots of the lesser wing of the sphenoid bone. It transmits the optic nerve and ophthalmic artery from the middle cranial fossa.The posterior aspect of the lateral wall (zygomatic and sphenoid bones) is demarcated by the superior and inferior orbital fissures, The superior orbital fissure lies between the greater and lesser wings of the sphenoid bone. It communicates with the middle cranial fossa and transmits cranial nerves III, IV, and VI, the three branches of the ophthalmic nerve, and the ophthalmic veins. The inferior orbital fissure communicates with the infratemporal and pterygopalatine fossae and transmits the zygomatic nerve. The lateral walls of the two orbits are set at approximately a right angle from one another, whereas the medial walls are nearly parallel to each otherThe floor (maxilla, zygomatic, and palatine bones) presents the infraorbital groove and canal for the nerve and artery of the same name. The inferior oblique muscle arises anteromedially, immediately lateral to the nasolacrimal canal.The medial wall (ethmoid, lacrimal, and frontal bones) is very thin. Its main component (the orbital plate of the ethmoid) is papyraceous (paper-thin). At the junction of the medial wall with the roof, the anterior and posterior ethmoidal foramina transmit the nerves and arteries of the same name.">