Name of bone



The ethmoid bone (from the Greek ethmos, meaning “sieve”) separates the nasal cavity from the brain. As such, it is located at the roof of the nose, between the two orbits; it is one of the bones that makes up the orbit of the eye. This cubical bone is lightweight due to a spongy construction.

Figure 1. Cranial bones

Figure 2. Ethmoid bone, frontal view

The ethmoid articulates with fifteen bones:

  • Four of the neurocranium: the frontal and the sphenoid (at the sphenoidal body and at the sphenoidal conchae)
  • Eleven of the viscerocranium: two nasal bones, two maxillae, two lacrimals, two palatines, two inferior nasal conchae, and the vomer

Muscle and ligament attachments

Surface anatomy


Physical examination




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 through 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.


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