Ethmoid bone

Last revised by Craig Hacking on 2 Jul 2021

The ethmoid bone is a single midline facial bone that separates the nasal cavity from the brain and is located at the roof of the nose and between the orbits. It is a cubical shape and is relatively lightweight because of its spongy construction and air-filled sinuses. It contributes to the anterior cranial fossa.

Gross anatomy

The ethmoid bone consists of four parts:

  • horizontal (cribriform) plate
  • vertical (perpendicular) plate
  • 2 lateral masses (labyrinths)

The horizontal plate features include:

The vertical plate forms the part of the bony nasal septum:

  • anterior border articulates with frontal bone and crests of nasal bones
  • posterior border features the sphenoidal crest which articulates with the vomer

Labyrinths (2) house anterior and posterior ethmoidal air cells.

  • lateral surface features include: the orbit, lamina papyracea, uncinate process below: medial wall of maxillary sinus which articulates with the inferior concha
  • medial surface features include: the nasal cavity, superior nasal concha, middle nasal concha helps form middle meatus, and the infundibulum opens there
  • upper surface: grooves articulate with frontal bone to form anterior and posterior ethmoidal canals

Articulates with 15 bones in total (4 cranial bones and 11 facial bones):

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