The frontal bone forms your forehead. It’s a single, shell-shaped bone that makes up the entire front of your skull, curving from your eyebrows up to the top of your head where your hairline begins. Beyond shaping the forehead, this bone also forms the roof of your eye sockets and houses a pair of air-filled cavities called the frontal sinuses.
Parts of the Frontal Bone
The frontal bone has four distinct sections, each serving a different purpose. The largest is the squamous part, the broad, curved plate whose outer surface creates the visible shape of your forehead. This is the part you feel when you touch your forehead.
Below and behind it sit two orbital plates, one above each eye. These thin, triangular pieces of bone extend backward from your brow line to form the ceiling of each eye socket, protecting the eyes from above. Between these orbital plates, a small nasal part projects downward and connects to the bridge of the nose.
Landmarks You Can Feel
Several features of the frontal bone are easy to locate on your own face. The supraorbital margin is the bony ridge running along the top of each eye socket. You can trace it with your fingertip from the inner corner of your brow outward. About one-third of the way from the inner edge, most people can feel a small notch or groove. This is the supraorbital notch, a passageway for a nerve and blood vessel that supply sensation and blood flow to the forehead and scalp.
The glabella is the smooth, flat area between your eyebrows. Its name comes from the Latin word for “hairless and smooth.” In younger people, it’s exactly that. With age, horizontal and vertical creases tend to form here. Just above the glabella on either side are the superciliary ridges, the bony prominences your eyebrows sit on. These ridges are one of the most visible differences between male and female skulls.
The Frontal Sinuses
Sandwiched inside the forehead portion of the frontal bone are two hollow spaces called the frontal sinuses. They sit between an outer layer of bone (the anterior table) and an inner layer (the posterior table) that separates the sinuses from the brain. These cavities are positioned above the eye sockets and behind the lower forehead.
Scientists aren’t entirely sure why the frontal sinuses exist. The leading theories suggest they lighten the weight of the skull and help cushion the brain from blunt-force impacts by dispersing incoming energy. They may also provide some protection for the eyes. Like other sinuses, they’re lined with mucous membrane and drain into the nasal passages, which is why a sinus infection can cause forehead pressure and pain.
How the Frontal Bone Connects to Other Bones
The frontal bone doesn’t float in isolation. It joins neighboring skull bones along seams called sutures. The most prominent is the coronal suture, a horizontal line that runs ear to ear across the top of the skull, connecting the frontal bone to the two parietal bones behind it. Along the sides, the frontal bone meets the zygomatic bone (cheekbone) at a small depression you can sometimes feel about 10 millimeters above the outer corner of your eye. It also connects to the nasal bones at the bridge of the nose, the lacrimal bones near the inner corners of the eyes, and the sphenoid and ethmoid bones deeper in the skull.
How the Frontal Bone Develops
You weren’t born with a single frontal bone. In infants, the forehead is actually made of two separate halves joined down the middle by a seam called the metopic suture. Unlike other skull sutures, which remain partially open throughout life, the metopic suture fuses and disappears early. In most children, closure begins around 4 months of age and is complete by 9 months, roughly the window between when a baby starts holding up their head and when they learn to sit upright. By the time a child reaches their first birthday, the two halves have typically merged into one solid bone.
Male and Female Differences
The frontal bone is one of the most useful bones for distinguishing male and female skulls. Male foreheads tend to slope backward more noticeably, while female foreheads are more vertical. Males also have more prominent brow ridges and a more projecting glabella. These two features, forehead slope and brow ridge size, combine to create a measurable difference. Studies using 3D skull models have found that measuring the angle of inclination from the glabella captures both traits at once. An inclination angle of about 78.2 degrees at the glabella reliably separates male from female skulls across multiple populations, making it a practical tool in forensic identification.
When the Frontal Bone Fractures
Because the forehead is an exposed, forward-facing part of the skull, the frontal bone is vulnerable to direct impacts from car accidents, falls, and sports injuries. Fractures are classified by which layer of bone breaks. The most common pattern, accounting for roughly a third of frontal sinus fractures, involves only the outer table. These fractures can sometimes heal on their own if the bone hasn’t shifted out of position. When the bone displaces more than 1 to 2 millimeters, the risk of a visible dent in the forehead increases, and surgical repair is more likely.
More serious injuries involve the inner table, the layer that sits directly against the brain’s protective membranes. As many as 33% of patients with frontal bone fractures develop a cerebrospinal fluid leak, where the clear fluid surrounding the brain drains through the nose. Combined fractures involving both the outer and inner tables, along with damage to the drainage pathway of the sinuses, make up 55 to 67% of cases and require more complex treatment. These injuries are relatively rare in everyday life but represent a well-known pattern in trauma medicine.