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The ethmoid bone (/ ˈ ɛ θ m ɔɪ d /; [1] [2] from Ancient Greek: ἡθμός, romanized: hēthmós, lit. '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.
In the ethmoid bone, a sickle shaped projection, the uncinate process, projects posteroinferiorly from the ethmoid labyrinth. Between the posterior edge of this process and the anterior surface of the ethmoid bulla , there is a two-dimensional space, resembling a crescent shape.
The ethmoidal labyrinth or lateral mass of the ethmoid bone consists of a number of thin-walled cellular cavities, the ethmoid air cells, arranged in three groups, anterior, middle, and posterior, and interposed between two vertical plates of bone; the lateral plate forms part of the orbit, the medial plate forms part of the nasal cavity.
The orbital lamina of ethmoid bone (or lamina papyracea or orbital lamina) is a smooth, oblong, [citation needed] paper-thin [1] bone plate [citation needed] which forms the lateral wall of the labyrinth of the ethmoid bone. [1] It covers the middle and posterior ethmoidal cells, and forms a large part of [citation needed] the medial wall of ...
The superior surface of the body of the sphenoid bone (Fig. 145) presents in front a prominent spine, the ethmoidal spine, for articulation with the cribriform plate of the ethmoid; behind this is a smooth surface slightly raised in the middle line, and grooved on either side for the olfactory lobes of the brain.
The ethmoid air cells consist of numerous thin-walled cavities in the ethmoidal labyrinth [4] that represent invaginations of the mucous membrane of the nasal wall into the ethmoid bone. [3] They are situated between the superior parts of the nasal cavities and the orbits, and are separated from these cavities by thin bony lamellae. [4]
Anatomical terms of bone [ edit on Wikidata ] The medial surface of the labyrinth of ethmoid consists of a thin lamella , which descends from the under surface of the cribriform plate , and ends below in a free, convoluted margin, the middle nasal concha ( middle nasal turbinate ).
The perpendicular plate of the ethmoid bone (vertical plate) is a thin, flattened lamina, polygonal in form, which descends from the under surface of the cribriform plate, and assists in forming the septum of the nose; it is generally deflected a little to one or other side. The anterior border articulates with the spine of the frontal bone and ...