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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.
In mammalian anatomy, the cribriform plate (Latin for lit. sieve-shaped), horizontal lamina or lamina cribrosa is part of the ethmoid bone.It is received into the ethmoidal notch of the frontal bone and roofs in the nasal cavities.
The frontal and sphenoid bones are towards the front middle of the skull and in front of the temporal bone. The ethmoid bone is the bone at the roof of the nose that separates the nasal cavity from the brain. It is a part of the dorsal cavity the cranial cavity and the spinal cord. The occipital bone is at the back of the skull.
The frontonasal duct may or may not drain into the ethmoidal infundibulum - this is determined by the place of attachment of the uncinate process of the ethmoid bone: if the uncinate process is attached to the lateral nasal wall, the frontonasal duct will open directly into the middle nasal meatus; if otherwise, it will drain into the infundibulum.
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 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]
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 ...