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Posterosuperior View of Articulated Frontal and Ethmoid Bones

Surgical Correlation


Posterosuperior view of articulated frontal and ethmoid bones. The frontal bone in the adult is a single bone having a horizontal or orbital portion that form the roofs of the orbital and nasal cavities and a larger vertical or squamous portion that forms most of the forehead. This bone unites along the coronal suture with the paired parietal bones and laterally with the zygomatic and greater wings of sphenoid. Along its posterior edge it articulates with lesser wings and body of the sphenoid. The U-shaped space in the posterior midline is the ethmoid notch for the cribriform plate of the ethmoid bone. The frontal lobes of the cerebrum rest upon its orbital surface. The ethmoid is a single, complex bone that occupies the central region of the viscerocranium. It has relationships with the orbit, nasal cavity, nasal septum, and anterior cranial fossa. It consists of two midline vertical projections, the crista galli and perpendicular plate, a pair of horizontal projections that form the roof of the nasal cavity, the cribriform plates, which connect to the ethmoid labyrinths. In this view, the crista galli projects superiorly and is one of sites of attachment of the falx cerebri. The perpendicular plate (not in view in this orientation) projects inferiorly to attach to the vomer and septal cartilage of the nasal septum. The cribriform plate is sieve-like with multiple foramina for transmission of the olfactory neurofilaments from the olfactory epithelium to olfactory bulbs that rest on the olfactory fossae of the cribriform plate. The labyrinth consists of two laminae that enclose a series of ethmoid air cells. The lateral or orbital lamina is thin (lamina papyracea) and forms part of the medial wall of the orbit. The medial or turbinal lamina bears the superior and middle turbinates along the lateral wall of the nasal cavity. The uncinate process is a crescent-shaped projection from the posteroinferior aspect of the ethmoid labyrinth. (Image courtesy of PA Rubino)