The frontal bone is the bone that shapes the forehead and contributes to the anterior portion of the human skull. Occupying the upper front of the cranium, it forms the forehead surface, the roofs of the eye orbits and part of the anterior cranial floor. The English name derives from Latin frons, meaning forehead. In adults it is usually a single bone, but during early life it develops from paired elements that normally fuse.

Anatomy and notable features

Anatomically the frontal bone is commonly described as having three principal regions: the squamous (vertical) portion that makes the visible forehead, the orbital (horizontal) portion that forms the orbital roofs and part of the nasal bridge, and a nasal portion that contributes to the root of the nose. Important surface landmarks include:

  • Supraorbital margin and the supraorbital foramen or notch, which transmit nerves and vessels to the forehead.
  • Frontal eminences (tubercles) and the glabella, used as external reference points.
  • Frontal sinuses, mucosa-lined cavities within the bone that vary widely in size and symmetry and open into the nasal cavity.
  • Articulations with the parietal bones at the coronal suture, with the nasal, zygomatic, maxillary, sphenoid and ethmoid bones.

Development, variation and evolution

The frontal bone forms by intramembranous ossification from paired centers that typically unite along the metopic suture during childhood; persistence of that suture into adulthood is called metopism. The frontal sinuses develop after birth and continue to grow through adolescence. Shape and projection of the frontal bone differ between individuals and populations; in the fossil record and comparative anatomy these differences are notable. For example, a pronounced supraorbital ridge or browridge is more prominent in earlier hominins and in Neanderthals — a trait that affected facial profile and may have had structural or display functions (Neanderthal browridge).

Function and clinical relevance

The frontal bone protects the frontal lobes of the brain and helps form the eye sockets. Clinically it is important in several contexts: frontal sinus infections (frontal sinusitis) can cause pain and require medical or surgical treatment; fractures of the frontal bone may involve the sinuses and the anterior cranial floor and need careful evaluation because of risks to the brain and orbit; cosmetic and reconstructive surgery often addresses forehead contour, brow position and sinus repair. Neurosurgical approaches to the anterior cranial fossa and orbital roof also work through or around the frontal bone.

Comparative notes and significance

Across vertebrates the morphology and number of frontal bones vary: many fishes and amphibians have paired frontal elements, while in mammals the frontal is typically a single expanded bone. In anthropology and forensic contexts the frontal bone contributes to assessments of age, sex and ancestry because of its contours, the prominence of glabella and browridges, and sinus patterns. For additional anatomical references and imaging examples, see resources on cranial anatomy and the anterior cranial fossa.

Overall, the frontal bone is both a visible feature of facial form and a complex cranial element with developmental, functional and clinical importance.