Anterior coronal view of the ethmoid bone and its relationship to the orbits. For orientation, superior is toward the bottom border of the image, anterior is facing the viewer. The roof and lateral walls of the orbit have been removed to expose orbital contents enclosed by periorbita. The frontal lobes of the cerebrum enclosed by dura have been reflected posteriorly and the superior sagittal sinus can be seen in the midline falx cerebri, which attaches inferiorly to the crista galli of the ethmoid bone. Superior frontal cerebral veins can be observed draining into this sinus. The ethmoid bone has three parts: cribriform plate, ethmoidal labyrinth of air cells, and perpendicular plate, and, hence, contributes structurally to the medial wall of the orbit, the nasal cavity, and nasal septum. Here, the cribriform plates lie on both sides of the crista galli and form the roof of the nasal cavity. Inferior to the crista galli is the perpendicular plate that forms the superior part of the nasal septum. The ethmoid labyrinth projects lateral to the perpendicular and cribriform plates and consists of the superior and middle conchae or turbinates along the lateral walls of the nasal cavity, and the orbital plates containing ethmoid air cells or sinuses. These plates articulate with the orbital plates of the frontal bone at the ethmoid notch. At this junction (frontoethmoidal suture) are located the anterior and posterior ethmoid foramina and canals that transmit the corresponding neurovasculature from the orbit to the ethmoid sinuses and nasal cavity. The lateral surface of the orbital plates (lamina papyracea) form much of the medial wall of the orbit; the medial surface borders the nasal cavity. The supraorbital arteries can be seen coursing anteriorly deep to the periorbita toward their foramina located on the superomedial margins of the orbit. (Image courtesy of AL Rhoton, Jr.)