noun, plural: ethmoid bones
The light cubical spongy bone lying between the orbits and at the top of the nasal cavity
The ethmoid bone is the bone in the skull located between the eyes, at the roof of the nose. It separates the nasal cavity from the brain and also forms part of the orbits.
It is made up of three parts, namely the cribriform plate, the ethmoidal labyrinths, and the perpendicular plate. The cribriform plate is the horizontal plate located within the middle section of the ethmoid bone. It has several perforations that allow the passage of olfactory nerve filaments from the nasal cavity. It also supports the olfactory bulb, which is the structure involved in olfaction. The ethmoidal labyrinths are paired lateral masses in the ethmoid bone. They are located laterally to the perpendicular plate. They contain series of ethmoid air cells that open into the nasal cavities. The perpendicular plate is the vertical plate that articulates with the vomer bone to form the nasal septum.
It articulates with these bones: frontal bone, body of the sphenoid bone, the sphenoidal conchae, nasal bones, maxillae, lacrimals, palatines, inferior nasal conchae, and vomer.
Baker et al. published a report suggesting that humans have deposits of ferric iron in the sphenoid/ethmoid sinus complex. These deposits may be magnetic and probably help to sense direction or to orient to ambient magnetic field.1
Word origin: Greek ethmos (sieve)
- os ethmoidale
- uncinate process of ethmoid bone
1Baker RR, Mather JG, & Kennaugh JH. Magnetic bones in human sinuses. Nature 301, 78 – 80 (06 January 1983); doi:10.1038/301078a0. Source