The Ethmoid

If the sphenoid is the most difficult cranial bone to describe and invision, the Ethmoid is the second most difficult. It has a number of features and projections, but unlike the sphenoid it cannot be seen from various views of the skull. Like the sphenoid, it is a single bone.

The "ethmoid bone" is located in front of the sphenoid bone. It consists of two masses, one on each side of the nasal cavity, which are joined horizontally by thin "cribriform plates." These plates form part of the roof of the nasal cavity, and nerves (ethmoidal cells) associated with the sense of smell pass through tiny openings in them. Portions of the ethmoid bone also form sections of the cranial floor, eye sockets, and nasal cavity walls. A "perpendicular plate" projects downward in the middle from the cribriform plates to form the bulk of the nasal septum. Delicate scroll-shaped plates called "superior" and "middle nasal conchae" project inward from the sides of the ethmoid bone toward the perpendicular plate. These bones, which are called the "turbinate bones," support mucous membranes that line the nasal cavity.

To view a QuickTime VR movie of the ethmoid bone click
The ethmoid touches, or articulates with, the following bones:

• Sphenoid
• Frontal
• Maxillae
• Palatines
• Vomer
• Lacrimals