The Frontal Bone

Frontal Bone AR Atlas

The frontal bone is a major bone of the cranium, and it forms the forehead, the roof of the orbits (eye sockets), and the anterior part of the cranial floor. It Articulates with the sphenoid, ethmoid, two parietals, two nasals, two maxillae, two lacrimals, and two zygomatic bones. (1)

Squamous part of frontal bone

External surface of squamous part of frontal bone

• External surface of squamous part of frontal bone: The external surface of squamous part of frontal bone is the outer surface of the squamous part of the frontal bone(1)
• Frontal eminence: The frontal tuber or frontal eminence is a rounded elevation located approximately 3cm above the supraorbital margin. It is positioned on either side of the squama’s middle line. (2,3)
• Superciliary arch: The two superciliary arches are elevations located just above the Supraorbital Margin. (1)
• Glabella: The glabella is an elevation located on the middle line between the Superciliary Arches. (1)
• Frontal part of orbital margin: The frontal part of the orbital mqrgin represents the lower boundary of the squama, and it separates the squama from the Orbital part. (1)
  • Supra-orbital foramen: In some cases, the Supraorbital notch presents as a hole rather than a notch; in these cases, it is named the Supraorbital Foramen (4)
  • Supra-orbital notch: the supraorbital notch is situated on the medial aspect of the supraorbital margin. (4)
  • Frontal notch: the frontal notch is a depression located medial to the supraorbital notch. (3,4)
  • Frontal foramen: In some cases, the frontal notch presents as a hole rather than a notch. In these cases, the Frontal notch is named the Frontal foramen. (1)

The temporal surface of the frontal bone

• Temporal surface of frontal bone: The temporal surface of frontal bone is represented by the lateral surface. (1)
• Parietal margin of frontal bone: The parietal margin of the frontal bone is the border that is oriented posteriorly and connects to the parietal bones (1)
• Temporal line: it is a line that continues the zygomatic process upwards and backwards. It divides into the upper and the lower temporal lines. (1)
• Zygomatic process of frontal bone: The zygomatic process of the frontal bone is the prominent structure that is situated at the lateral end of the supraorbital margin. It serves for the articulation with the Zygomatic bone. (1)

Internal surface of the squamous part of the frontal bone

• Frontal cres­­t­­­­­­­­: The frontal crest is a ridge­ located on the lower end of the midline that results from the union of the edges of the sagittal sulcus. (3)
• Foramen caecum of frontal bone: Formaen caecum is a foramen that results from the union of a small notch with the ethmoid bone. The notch is located at the inferior end of the frontal crest. (2,5)

The nasal part of the frontal bone

• The nasal part of the frontal bone: The nasal part of the frontal bone is a downward continuation of the Sqama, located just between the Supraorbital Margins. (1)
• Nasal spine of frontal bone: The nasal spine of the frontal bone is a bony projection that projects downwards from the centre of the nasal part. It articulates with the nasal bones and with the perpendicular plate of the ethmoid bone. (2,5)
• Nasal margin of frontal bone: The nasal margin of the frontal bone is the lower border of the Nasal part of the frontal bone. It articulates with the upper borders of the nasal bones. (2,5)

The orbital part of the frontal bone

• The nasal part of the frontal bone: The nasal part of the frontal bone is the horizontal part of the frontal bone. It is formed by two triangular plates separated by a gap. (1)
• Orbital plate of frontal bone: The orbital plates are the triangular plates that are positioned on either side of the Ethmoidal notch. (2,5)
• Orbital surface of frontal bone: The orbital surface is the internal surface of the orbital plate. (2,5)
  • Trochlear spine: The trochlear spine is a small bony prominence located on the medial side of this surface. (2,5)
  • Trochlear fovea: The trochlear fovea is a small depression located medially on the orbital surface of the frontal bone, next to the nasal part. (2,5)
  • Fossa for lacrimal gland: The fossa for the lacrimal gland is a shallow depression located laterally on the orbital surface of the frontal bone, next to the zygomatic process (2,5)

• Sphenoidal margin of frontal bone: The sphenoidal margin is the margin that connects to the great wing of the sphenoid. It is triangular in shape (2,5)
• Ethmoidal notch: The ethmoidal notch is the gap that separates the triangular plates. It is located on the midline of the orbital part. It articulates with the ethmoid bone. (2,5)

• Sinus of frontal bone: The sinuses of the frontal bone are two cavities situated in the frontal bone, irregular in shape and separated by a thin bone. (2,5)
• Opening of frontal sinus: The opening of the frontal sinus is located on either side of the nasal spine of the frontal bone, just anterior to the Ethmoidal notch. (2,5)
• Septum of frontal sinuses: The septum of frontal sinuses is a thin bony septum that separates the sinuses of the frontal bone. (2)

Bibliography

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The structure and organization of anatomical terms used in this text follow the guidelines provided by FIPAT (2019) in their publication: FIPAT. (2019). Terminologia Anatomica (2nd ed.). FIPAT.library.dal.ca. Federative International Programme for Anatomical Terminology. Retrieved May 7, 2023, from https://fipat.library.dal.ca/TA2/