etmoide

The ethmoid bone, known as etmoide in several languages, is a light, spongy bone located between the nasal cavity and the orbits. It contributes to the medial wall of the orbits, the roof of the nasal cavity, and the floor of the anterior cranial fossa. It forms part of the nasal septum via its perpendicular plate, which articulates with the vomer. The bone consists of three main parts: the cribriform plate; the perpendicular plate; and the ethmoidal labyrinth, a network of interconnected air cells that form the lateral mass. The labyrinth bears the superior and middle nasal conchae and contributes to the medial wall of the orbit and the posterior wall of the nasal cavity.

The cribriform plate is a horizontal portion of the anterior skull base perforated by olfactory foramina for olfactory nerve fibers. The perpendicular plate descends to join the vomer in forming the nasal septum. The ethmoidal labyrinth contains the ethmoidal air cells, which drain into the middle and, to a lesser extent, the superior meatus. The bone articulates with the frontal, sphenoid, lacrimal, nasal, maxillary, palatine bones, and the vomer.

Vascular and nerve supply: the anterior and posterior ethmoidal arteries (branches of the ophthalmic artery) supply the bone; sensory innervation is via the anterior and posterior ethmoidal nerves (branches of the nasociliary nerve, V1).

Clinical relevance: the ethmoid is part of the paranasal sinuses; ethmoiditis refers to infection of the ethmoidal air cells. Fractures involving the cribiform plate can cause cerebrospinal fluid leakage and risk injury to the olfactory nerves; ethmoid fractures can occur with orbital or skull-base trauma. Ethmoidectomy is a surgical procedure to treat sinus disease.