etmoïde

The etmoid bone is a complex, unpaired bone located at the root of the skull between the orbits. It forms part of the cranial cavity, the nasal cavity, and the orbits. It is a very light and spongy bone, contributing to the overall structure of the head.

The etmoid bone is comprised of several distinct parts. The cribriform plate is a horizontal portion that separates the cranial cavity from the nasal cavity and contains numerous small foramina for the passage of olfactory nerves. Superior to the cribriform plate is the crista galli, a prominent crest that serves as an attachment point for the dura mater.

Laterally, the ethmoid bone forms the ethmoidal labyrinths, which contain the ethmoidal air cells or sinuses. These sinuses are small, air-filled cavities that are lined with mucous membrane and connect to the nasal cavity. The ethmoid bone also contributes to the formation of the superior and middle nasal conchae, which are scroll-like bony projections that increase the surface area of the nasal cavity, aiding in warming, humidifying, and filtering inhaled air. Its delicate structure makes it susceptible to fractures.