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 thirteen bones:
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
cribriform 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.
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
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.
Additional images
See also
References
External links
- http://www.theregister.com/2006/11/17/the_odd_body_nose_compass/
