The ethmoid bone (os ethmoidale) is an unpaired bone of the neurocranium, although most of it makes up the viscerocranium. The ethmoid bone is located centrally between the bones of the visceral cranium and comes in contact with most of them to form the nasal and orbital cavities. The bony plates of the ethmoid bone are arranged in the form of the letter “T”, in which the vertical line is formed by the perpendicular plate and the horizontal one is formed by the cribriform plate. From the cribriform plate and on each side of the horizontal plate hang the ethmoidal labyrinths.
The ethmoid bone consists of four parts: