Frontal bone

Last revised by Joachim Feger on 11 May 2024

The frontal bone is a skull bone that contributes to the cranial vault. It contributes to form part of the anterior cranial fossa.

The frontal bone has two portions:

  • vertical portion (squama): has external/internal surfaces

  • horizontal portion (orbital): has superior/inferior surfaces

The external surface of the vertical portion features:

Internal surface of the vertical portion features:

  • sagittal sulcus: vertical groove for the superior sagittal sinus

  • frontal crest: ridge, formed from edges of sulcus that gives attachment to the falx cerebri

  • foramen cecum: small notch, converted into foramen, emissary vein from nose

  • groove for anterior meningeal artery (branch of anterior ethmoidal artery)

The horizontal portion is composed of two thin, orbital plates separated by the ethmoidal notch.

The inferior surface of the horizontal portion is smooth and concave. It features:

  • lacrimal fossa: lateral shallow depression for lacrimal gland

  • fovea trochlearis / trochlear spine near nasal part, for attachment of cartilaginous pulley for superior oblique muscle

The superior surface of the horizontal portion is convex and contains depressions for cerebral convolutions. It features:

  • openings for the frontal sinuses on either side of the nasal process; each frontal sinus communicates with the ipsilateral middle nasal meatus via a frontonasal duct

  • two grooves converted into anterior and posterior ethmoidal canals when articulating with the ethmoid bone

The frontal bone articulates with twelve bones.

Unpaired bones include:

Paired bones include:

  • nasal: via either side of the midline of the nasal notch

  • frontal process of the maxilla: via the lateral portion of nasal notch

  • lacrimal: via lateral portion of nasal notch

  • parietal: via border of squama

  • zygomatic: via zygomatic processes

The frontal bone undergoes intramembranous ossification. The metopic suture fuses in 2nd year but may persist.

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