Ethmoid Bone Structure and Function

Ethmoid Bone Characteristics

• The ethmoid bone is a porous bone that forms the major portion of the middle part of the face between the orbits.
• It helps form the orbit, nasal cavity, nasal septum, and anterior cranial fossa.
• There is only one ethmoid bone.

Parts of the Ethmoid Bone

Perpendicular Plate

• A flat plate that descends from the cribriform plate to form part of the nasal septum.
• It articulates with the vomer inferiorly.

Cribriform Plate

• A horizontal bone that forms the superior surface of the ethmoid.
• It contains numerous foramina for the olfactory nerve.
• The crista galli is a vertical plate that extends superiorly from the cribriform plate, providing attachment for the falx cerebri of the meninges.
• It is associated with a small foramen cecum.

Ethmoid Labyrinth

• The largest part of the ethmoid bone.
• It descends inferiorly from the cribriform plate.
• The ethmoid paranasal sinuses are located within the ethmoid labyrinth.
• The ethmoid labyrinth forms two major structures within the nasal cavity:
  • Superior nasal concha.
  • Middle nasal concha.
• The ethmoid bulla is a large elevation of bone located near the middle ethmoid paranasal sinuses.
• The uncinate process is a curved piece of bone.
• The hiatus semilunaris is located between the uncinate process and the ethmoid bulla.

Ethmoid Bone Characteristics

• The ethmoid bone is a porous bone that forms the major portion of the middle part of the face between the orbits.
• It helps form the orbit, nasal cavity, nasal septum, and anterior cranial fossa.
• There is only one ethmoid bone.

Parts of the Ethmoid Bone

Perpendicular Plate

• A flat plate that descends from the cribriform plate to form part of the nasal septum.
• It articulates with the vomer inferiorly.

Cribriform Plate

• A horizontal bone that forms the superior surface of the ethmoid.
• It contains numerous foramina for the olfactory nerve.
• The crista galli is a vertical plate that extends superiorly from the cribriform plate, providing attachment for the falx cerebri of the meninges.
• It is associated with a small foramen cecum.

Ethmoid Labyrinth

• The largest part of the ethmoid bone.
• It descends inferiorly from the cribriform plate.
• The ethmoid paranasal sinuses are located within the ethmoid labyrinth.
• The ethmoid labyrinth forms two major structures within the nasal cavity:
  • Superior nasal concha.
  • Middle nasal concha.
• The ethmoid bulla is a large elevation of bone located near the middle ethmoid paranasal sinuses.
• The uncinate process is a curved piece of bone.
• The hiatus semilunaris is located between the uncinate process and the ethmoid bulla.