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Frontal bone

German: Os frontale

1 Definition

The frontal bone is a shell-shaped skull bone, which represents the bony base of the upper edge of the orbita and the forehead, among others.

2 Anatomy

The frontal bone can be divided roughly into two parts:

  • Squama frontalis (squamous part)
  • Pars orbitalis (orbital part)

Some authors also delimitate the Pars nasalis (nasal part) as third part, which forms the middle part between both orbital parts.

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2.1 Squama frontalis

The Squama frontalis or squamous part forms the bony frame of the forehead. You can differentiate between a convex external surface (Facies externa) and a concave internal surface (Facies interna) who have characteristic structures each.

2.1.1 Facies externa

The Facies externa is curved and shows the frontal suture (Sutura metopica) in the midline, which parts the bone in two during childhood. On both sides, you can find the frontal eminence in around 3 cm of distance. This eminence also called tuber frontale can vary significantly between individuals, and it mainly appears in children.

Below the eminence, separated by a flat hollow in the bone, there are the two superciliary arches (Arcus superciliares) which are connected to each other in the middle of the bone via the glabella. In men, the arches are more prominently developed than in women. Further in caudal direction, the squamous part ends in a curved bony crest, the supraorbital margin, which forms the upper edge of the orbita. It separates the squamous part from the adjacent orbital part.

2.1.2 Facies interna

The Facies interna is concave and presents a vertical crest in the upper part of its midline, the superior sagittal sulcus, which accommodates the superior sagittal sinus. The falx cerebri inserts at the protruding edges of the sulcus. Further caudally, both these bone crests fuse and form the frontal crest, which finally terminates in a small hollow, the foramen caecum.

On both sides of the sulcus, there are numerous cavities for the accommodation of the convolutions of the brain, and small grooves which accommodate the branches of the middle meningeal artery.

2.2 Pars orbitalis

The orbital part forms the roof of the orbita and nasal cavity. It consists of two relatively thin, almost triangular bone plates, the orbital plates, and the recess for the ethmoid bone in between.

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Specialties: Anatomy

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