Ethmoid bone

Dr Jeremy Jones et al.

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 two orbits. It is a cubical shape and is relatively lightweight because of its spongy construction. 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:

  • foramina in cribiform plate: for olfactory nerve filaments (20), olfactory bulb overlies
  • crista galli (Latin for rooster's crest): thick, smooth triangular process, attachment for falx cerebri
  • nasal slits: anteriorly, passage of anterior ethmoidal nerve

The vertical plate forms the 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, middle, posterior ethmoidal cells.

  • lateral surface features include: the orbit, lamina papyracea, uncinate process below: medial wall of maxillary sinus which articulates with inferior conchae
  • 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
Articulations

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

Cranial bones include: frontal, sphenoid, and sphenoidal conchae (2). The facial bones are paired or unpaired. The single unpaired (1) bone is the vomer. Paired bones (2) include: nasal, maxilla, lacrimals, palatines, inferior nasal conchae.


Head and neck anatomy
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Article Information

rID: 4785
System: Head & Neck
Section: Anatomy
Synonyms or Alternate Spellings:

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    Figure 1: sagittal section of the skull
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    Figure 2: orbital bones
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    Figure 3
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    Figure 4: posterior view
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    Figure 5: skull and facial bones
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