Ethmoid

Ethmoid bone
Cranial bones
The seven bones which articulate to form the orbit. (Ethmoid is brown, between the red and the purple marked bones)
Details
Identifiers
Latin	os ethmoidale
MeSH	A02.835.232.781.292
TA	A02.1.07.001
FMA	52740
Anatomical terms of bone []

The ethmoid bone (/ˈɛθmɔɪd/; from Greek ethmos, "sieve") is an unpaired bone in the skull that separates the nasal cavity from the brain. It is located at the roof of the nose, between the two orbits. The cubical bone is lightweight due to a spongy construction. The ethmoid bone is one of the bones that make up the orbit of the eye.

The ethmoid bone is an anterior cranial bone located between the eyes. It contributes to the medial wall of the orbit, the nasal cavity, and the nasal septum. The ethmoid has three parts: cribriform plate, ethmoidal labyrinth, and perpendicular plate. The cribriform plate forms the roof of the nasal cavity,the ethmoidal labyrinth consists of a large mass on either side of the perpendicular plate, and the perpendicular plate forms the superior two-thirds of the nasal septum. Between the orbital plate and the nasal conchae are the ethmoidal sinuses or ethmoidal air cells, which are a variable number of small cavities in the lateral mass of the ethmoid.

The ethmoid articulates with thirteen bones:

The ethmoid is ossified in the cartilage of the nasal capsule by three centers: one for the perpendicular plate, and one for each labyrinth.

The labyrinths are first developed, ossific granules making their appearance in the region of the lamina papyracea between the fourth and fifth months of fetal life, and extending into the conchæ.