The frontal bone is an unpaired bowl-shaped bone located in the forehead, contributing to the anterior cranial shape. It lies superior to the nasal bones and anterior to the parietal bones. It not only forms the forehead and protects the brain but also participates in forming the orbit, nose, and anterior cranial fossa.

The frontal bone has four parts:

Squamous part

The squamous part is the largest part of the frontal bone, forming the forehead. It is located superior to both orbits and nasal bones.

It has two surfaces - inner (internal) and outer (external) surface.

The outer surface contains several landmarks:

Just superior to the rim of the orbit on each side are the raised superciliary arches. These are more pronounced in men than in women. Between these arches above the nasal bones is a small depression - the glabella.

The inferior border of the superciliary arches forms the superior border of the orbit called the supraorbital margin. It contains two structures.

The frontal notch or foramen is located more medial on the border, while lateral to it is the supraorbital foramen (or supraorbital notch).

Every lateral end of the supraorbital margin contains a zygomatic process that articulates with the zygomatic bone. From the zygomatic process starts the temporal line, which goes up and back and passes into the superior temporal line of the parietal bone. Below the temporal line is located the temporal surface.

The external surface of the squamous part also contains frontal tuber or eminence, a rounded elevation located few centimeters above the supraorbital margin, and superciliary arches on both sides.

The internal surface of the squamous part is concave, and it includes these structures:

Frontal crest - median vertical ridge located in the lower aspect of the squamous part;
Groove for superior sagittal sinus - a vertical groove superior to the frontal crest, located in the midline of the upper part; it goes upward; it lodges the superior sagittal sinus.

The edges of the sinus and the frontal crest are connected to the falx cerebri.

Orbital part

The orbital part of the frontal bone is plate-shaped, and it separates the cranial cavity from the orbit. It forms the roof of the orbit. Therefore it has two surfaces - the orbital surface that faces the orbit and the cerebral surface facing the brain.

The orbital surface on its lateral part contains a fossa of the lacrimal gland, where the lacrimal gland is located, while posterior to it and more on the medial aspect are located two openings named the anterior and posterior ethmoidal foramina. They are located on the borderline with the ethmoid bone, therefore the ethmoid bone also participates in forming these openings. Anterior and posterior ethmoidal nerves (arising from the nasociliary nerve), as well as ethmoidal arteries and veins pass through the mentioned foramina.

The ethmoidal notch is located in the middle between both orbital parts. From above, it is covered by the cribriform plate of the ethmoidal bone.

Nasal part

The nasal part is the smallest of all three, and it is located between both orbital parts anterior to the ethmoidal notch. Together with the nasal bones, this part forms an area called the nasion or the bridge of the nose.

The frontal bone contains paired air-filled cavities called frontal sinuses. Both sinuses are not the same in size and shape. There is a septum between both sinuses, which separates them.

Sometimes in the middle of the lower aspect of the squamous part and the nasal parts the metopic suture is present as a remain of the frontal suture in newborns.

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Frontal bone