Bone: Ethmoid bone
Cranial bones
The seven bones which articulate to form the orbit. (Ethmoid is brown)
Latin	os ethmoidale
Gray's	subject #36 153
MeSH	Ethmoid+bone

The ethmoid bone (from Greek ethmos, "sieve") is a bone in the skull that separates the nasal cavity from the brain. As such, it is located at the roof of the nose, between the two orbits. The cubical bone is lightweight due to a spongy construction.

Articulations

The ethmoid articulates with fifteen bones:

• four of the cranium—the frontal, the sphenoid, and the two sphenoidal conchae
• eleven of the face—the two nasals, two maxillae, two lacrimals, two palatines, two inferior nasal conchae, and the vomer

Injuries

The ethmoid bone is very delicate and is easily injured by a sharp upward blow to the nose, such as a person might suffer by striking an automobile dashboard in a collision. The force of a blow can drive bone fragments through the cribiform plate into the meninges or brain tissue. Such injuries are often evidenced by leakage of cerebrospinal fluid into the nasal cavity, and may be followed from the nasal cavity to the brain.

Sagittal section of the skull. Ethmoid bone is labeled with white

Blows to the head can also shear off the olfactory nerves that pass though the ethmoid bone and cause anosmia, an irreversible loss of the sense of smell and a great reduction in the sense of taste (most of which depends on smell). This not only deprives life of some of its pleasures, but can also be dangerous, as when a person fails to smell smoke, gas, or spoiled food.

Fracture of the lamina papyracea, the lateral plate of the ethmoid labyrinth bone, permits communication between the nasal cavity and the ipsilateral orbit through the inferomedial orbital wall, resulting in orbital emphysema. Increased pressure within the nasal cavity, as seen during sneezing, for example, leads to temporary exophthalmos.

Role in magnetoception

Main article: Magnetoception

Some birds and other migratory animals have deposits of biological magnetite in their ethmoid bones which allow them to sense the direction of the Earth's magnetic field. Humans have a similar magnetite deposit, but it is believed to be vestigial. ^[1]

Additional images

Ethmoid bone from above.	Perpendicular plate of ethmoid.	Ethmoid bone (frontal view).	Ethmoid bone from the right side.
Sphenoid bone visible center right.	Side view of the skull.	The skull from the front.	Medial wall of left orbit.
Base of the skull. Upper surface.	Medial wall of left nasal fossa.	Roof, floor, and lateral wall of left nasal cavity.	Lateral wall of nasal cavity, showing ethmoid bone in position.

See also

• Ossification of ethmoid
• Bone terminology
• Terms for anatomical location

References

1. "Evidence of a nonlinear human magnetic sense.".

External links

• http://www.theregister.com/2006/11/17/the_odd_body_nose_compass/
• Roche Lexicon - illustrated navigator, at Elsevier 34256.000-1

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.

The Bones which form the Orbit Frontal bone • Zygomatic bone • Maxillary bone • Sphenoid bone • Ethmoid bone • Palatine bone • Lacrimal bone

Source: adapted by the editor from Wikipedia, the free encyclopedia; from the article "Ethmoid bone". Image Credit.

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