The frontal bone is the broad, curved bone that forms the forehead, the upper portion of the eye sockets, and much of the front part of the skull. It plays an essential role in protecting the brain, supporting the structures around the eyes, and shaping the upper face. Although it appears to be a single solid bone in adults, its anatomy includes several distinct regions, internal spaces, and connections with neighboring bones.
Understanding the frontal bone helps explain how the skull protects delicate tissues, how facial features develop, and why injuries or disorders affecting the forehead can sometimes involve more than the visible surface of the head.
Where is the frontal bone located?
The frontal bone sits at the front of the skull, above the eyes and in front of the brain. It extends from the forehead upward toward the top of the head and downward to form the roof of each orbit, the bony cavity that contains an eye and its associated muscles, nerves, blood vessels, and connective tissues.
Its position places it at the intersection of the braincase and the facial skeleton. The upper portion contributes to the cranial vault, the dome-like structure surrounding the brain. The lower portion helps form the superior orbital margins, which are the bony ridges above the eyes, as well as parts of the orbital roofs and the nasal region.
The frontal bone connects with several other skull bones. These include the two parietal bones toward the top and back of the skull, the sphenoid bone behind the eye sockets, the ethmoid bone between the orbits, the nasal bones at the bridge of the nose, and the paired maxillary and lacrimal bones near the inner eye sockets. It also articulates with the zygomatic bones, which contribute to the cheekbones and the outer boundaries of the orbits.
Anatomists use the term articulation to describe a place where bones meet. Most of the connections between the frontal bone and neighboring skull bones are immovable joints called sutures. These fibrous connections help hold the skull together while allowing for growth during development.
The main parts of the frontal bone
The frontal bone is commonly divided into three principal regions: the squamous part, the orbital parts, and the nasal part. Each contributes to a different aspect of skull structure and function.
The squamous part
The squamous part is the large, curved, plate-like portion that forms most of the forehead and the front of the cranial vault. The word squamous refers to a thin, flattened structure.
Its outer surface gives the forehead much of its underlying bony shape. This surface varies naturally among individuals, contributing to differences in forehead contour, brow prominence, and overall facial appearance.
Several landmarks can be identified on the external surface. The frontal eminences are rounded elevations that are often noticeable on either side of the upper forehead. The superciliary arches are curved ridges above the eye sockets that contribute to the shape of the eyebrows. Their prominence varies with age, individual anatomy, and other factors.
Between the superciliary arches is the glabella, a relatively smooth area of bone between the eyebrows and above the bridge of the nose. The glabella serves as an important anatomical reference point in examinations of the face and skull.
The squamous part also has an internal surface facing the brain. This surface is shaped in part by the underlying contours of the frontal lobes, the forward portions of the cerebral hemispheres. It contains grooves and impressions associated with blood vessels and other structures that lie against the inner skull.
The orbital parts
The orbital parts are two roughly horizontal plates that extend backward from the upper orbital margins. Their lower surfaces form much of the roofs of the eye sockets, while their upper surfaces contribute to the floor of the anterior cranial fossa, the shallow region at the front of the skull’s internal base that supports the frontal lobes.
This arrangement places the brain directly above the orbital cavities, with the frontal bone separating the two regions. The bone therefore provides structural support and a protective barrier between the contents of the skull and the structures surrounding the eyes.
The orbital plates are thin compared with some other portions of the skull. Their shape accommodates the eye sockets and neighboring tissues while maintaining the separation between the orbits and the cranial cavity.
Near the inner portion of each orbital roof is the trochlear fovea or, in some individuals, a small trochlear spine. These features provide attachment for the trochlea, a small pulley-like structure associated with the superior oblique muscle of the eye. The trochlea redirects the muscle’s tendon, helping the eye move in a coordinated manner.
Near the outer portion of each orbital roof is the lacrimal gland fossa, a shallow depression that accommodates the lacrimal gland. This gland produces much of the watery component of tears, which help lubricate and protect the eye’s surface.
The nasal part
The nasal part is a relatively small region of the frontal bone located between the orbital plates, near the root of the nose. It contributes to the upper boundary of the nasal opening and connects with the nasal bones and parts of the maxilla and ethmoid.
Although small compared with the squamous and orbital parts, this region helps integrate the forehead with the bony framework of the nose and the upper nasal cavity.
Internal structure of the frontal bone
Like other bones of the skull, the frontal bone contains layers of compact bone surrounding a more porous internal region in many areas. Its internal architecture balances strength with relatively low weight.
The outer and inner tables are layers of dense, compact bone. Between them lies the diploë, a layer of spongy bone containing marrow spaces and small blood vessels. The diploë helps absorb and distribute mechanical forces, while the compact tables provide a firm external and internal framework.
The thickness of these layers varies across the bone. The frontal region is not uniformly thick, and the orbital plates are generally thinner than portions of the forehead. These differences reflect the distinct structural demands of the skull’s various regions.
The inner surface of the frontal bone contains grooves for blood vessels and impressions associated with the brain’s contours. A prominent midline groove may accommodate the superior sagittal sinus, a large venous channel that drains blood from the brain. Near this groove is the frontal crest, a ridge of bone that can provide attachment for the falx cerebri, a fold of dura mater that separates the two cerebral hemispheres.
The dura mater is the tough outermost membrane surrounding the brain and spinal cord. The relationship between the frontal bone, its internal landmarks, and this membrane illustrates how the skull is integrated with the protective tissues of the central nervous system.
The frontal sinuses and their role
One of the most distinctive features of the frontal bone is the presence of the frontal sinuses in many adults. These are air-filled cavities located within the bone, typically above the inner portions of the eye sockets and behind the lower forehead.
The frontal sinuses are part of the paranasal sinus system, which also includes the maxillary, ethmoid, and sphenoid sinuses. They are lined with a mucous membrane containing cells that produce mucus and cilia, tiny hair-like structures that move mucus toward drainage pathways.
The frontal sinuses usually drain into the nasal cavity through narrow channels associated with the frontal recess and the drainage pathway of the middle nasal meatus. This arrangement allows mucus and trapped particles to move out of the sinus rather than accumulating indefinitely.
The sinuses vary considerably in size and shape. They may differ between the left and right sides, and in some people one or both may be very small or absent. Their development begins during childhood, and their size and configuration continue to change as the skull grows.
The precise biological advantages of the paranasal sinuses are not completely settled. Proposed functions include contributing to the conditioning of inhaled air, influencing voice resonance, and reducing the weight of parts of the skull. Their mucus-producing lining also participates in the respiratory system’s defenses. No single proposed explanation fully accounts for every aspect of sinus anatomy.
When the lining of a frontal sinus becomes inflamed, often during a respiratory infection or because of impaired drainage, mucus may accumulate and pressure or pain may develop in the forehead region. This condition is commonly associated with frontal sinusitis, a type of sinus inflammation.
Because the frontal sinuses lie within the frontal bone, disease affecting them can occasionally extend beyond the sinus cavity. Serious complications are uncommon but may involve nearby orbital tissues or, in rare cases, structures within the skull.
How the frontal bone develops
The frontal bone begins forming before birth through a process called intramembranous ossification. In this process, bone develops directly within a sheet of embryonic connective tissue rather than first replacing a cartilage model.
The frontal bone initially develops as right and left halves. These halves are separated by the metopic suture, which runs down the midline of the forehead. After birth, the two sides gradually approach one another and usually fuse during early childhood.
The metopic suture typically closes during infancy or early childhood, although the timing varies. In some people, it remains visible throughout life as a persistent metopic suture. This can be a normal anatomical variation.
Premature fusion of the metopic suture is called metopic craniosynostosis. Because skull sutures help direct skull growth, early fusion can alter the shape of the forehead and the front portion of the skull. The resulting appearance depends on the degree and pattern of fusion and may require specialist evaluation.
The other sutures connecting the frontal bone to neighboring bones generally remain identifiable throughout life, even as the skull matures. During childhood, these joints allow the skull to expand as the brain grows. Once growth is largely complete, they continue to provide stable connections between the bones.
The frontal sinuses develop separately from the initial formation of the bone. They emerge as air-filled extensions of the nasal cavity and gradually enlarge during childhood and adolescence. This explains why the frontal sinuses are generally much less developed in young children than in adults.
The main functions of the frontal bone
The frontal bone performs several closely related functions that support the brain, the eyes, and the overall structure of the face.
Protecting the brain
The frontal bone forms the front of the bony enclosure surrounding the brain. Its curved squamous part protects the frontal lobes from many external impacts, while its orbital plates form a barrier between the brain and the eye sockets.
The skull does not prevent every injury, but it helps distribute mechanical forces and reduces the likelihood that ordinary impacts will directly damage delicate neural tissue. The scalp, meninges, cerebrospinal fluid, and other structures also contribute to protection.
The frontal bone is particularly important because the frontal lobes participate in executive functions, planning, voluntary movement, aspects of language, attention, and behavior. Protecting this region helps safeguard brain structures essential to everyday functioning.
Supporting and protecting the eyes
The orbital portions form much of the upper boundaries and roofs of the eye sockets. These bony surfaces help maintain the position of the eyes and shield the orbital contents from some external forces.
The superior orbital margins also contribute to the contours of the brow. Together with the soft tissues of the forehead and eyelids, these structures help define the upper facial region.
The frontal bone’s orbital landmarks also accommodate structures involved in eye movement and tear production, illustrating its role as a supporting framework for the visual system.
Shaping the forehead and upper face
The external surface of the frontal bone provides the foundation for the forehead and much of the brow region. Its curvature, thickness, and ridges influence the appearance of the upper face.
Soft tissues, including skin, muscles, connective tissue, and fat, cover the bone and contribute to the final facial contour. Differences in the frontal bone are therefore only one part of the reason forehead shapes vary among individuals.
The frontal bone also connects the cranial vault with the bones of the face, creating a continuous framework that supports facial proportions and the position of the orbits and nasal region.
Providing attachment and passageways for structures
The frontal bone contains landmarks associated with muscles, membranes, blood vessels, nerves, and other tissues. Its internal ridges and grooves help accommodate structures associated with the brain and its protective coverings.
A small opening or notch near the superior orbital margin, known as the supraorbital foramen or notch, allows the supraorbital nerve and accompanying blood vessels to pass from the orbit toward the forehead and scalp. The nerve supplies sensation to portions of the forehead and scalp.
These openings and grooves are important because nerves and blood vessels must travel between protected spaces and the surrounding tissues without being obstructed by bone.
Contributing to the structure of the nasal and sinus regions
The frontal bone forms part of the framework surrounding the upper nasal cavity and houses the frontal sinuses when they are present. Through these relationships, it contributes to the architecture of the upper respiratory passages and the separation between the nasal region and the cranial cavity.
The frontal sinuses also connect anatomically with the nasal drainage system. Their location means that inflammation or blockage can cause symptoms around the forehead and inner eye region.
The frontal bone and common injuries
The frontal bone is relatively well protected by the surrounding scalp and soft tissues, but a sufficiently strong impact can cause a fracture. The consequences depend on the location, severity, and direction of the force, as well as whether nearby structures are affected.
A fracture involving the thick forehead region differs from one involving the thinner orbital plates or the walls of the frontal sinuses. Some injuries are confined largely to the bone, while others may involve the eye sockets, the sinus cavities, the meninges, or the brain.
A frontal bone fracture does not automatically mean that the brain has been injured. However, the two can occur together, and the absence of a visible wound does not rule out a serious head injury.
Warning signs after a significant head impact include loss of consciousness, confusion, repeated vomiting, worsening headache, seizure, weakness, unequal pupils, or clear fluid draining from the nose or ears. These symptoms require urgent medical assessment. A suspected skull fracture or significant head injury should be evaluated promptly, even if the external injury appears limited.
The frontal sinuses introduce additional considerations. A fracture involving a sinus may disrupt its drainage, damage its walls, or create a pathway between the sinus and neighboring structures. Treatment depends on the fracture pattern and the presence of complications; not every frontal bone fracture requires surgery.
Disorders and anatomical variations
The frontal bone differs naturally in thickness, contour, and the prominence of its ridges. Frontal eminences and brow ridges can be subtle or pronounced, and frontal sinus anatomy can vary substantially between individuals. Such differences are often normal and do not, by themselves, indicate disease.
Developmental conditions can alter the bone’s shape. Metopic craniosynostosis is one example, resulting from premature fusion of the metopic suture. Other conditions affecting bone growth or skull development can also influence the forehead’s contour.
The frontal bone may also be affected by disorders that influence bones more generally, including metabolic diseases, infections, benign growths, and tumors. Their effects depend on the underlying condition and may include changes in bone density, localized swelling, pain, or structural abnormalities.
Problems involving the frontal sinuses are often more common than diseases originating in the bone itself. Sinus inflammation can cause pressure or discomfort over the forehead, particularly when drainage is impaired. However, forehead pain has many possible causes, including tension-type headaches, migraine, eye strain, and other conditions. Pain in this area alone cannot establish that the frontal sinuses or the frontal bone are responsible.
When clinicians need to evaluate the frontal bone in detail, computed tomography (CT) is often useful because it provides clear images of bone, fractures, sinus cavities, and the surrounding skull anatomy. Magnetic resonance imaging (MRI) is more useful for many questions involving the brain and other soft tissues. The appropriate examination depends on the symptoms, suspected condition, and clinical findings.
Why the frontal bone matters
The frontal bone is more than the structure beneath the forehead. It is a complex component of the skull that protects the frontal lobes, forms the roofs of the eye sockets, supports the upper face, and accommodates nerves, blood vessels, and the frontal sinuses.
Its development also demonstrates how the skull changes over time. The initially separate halves of the bone fuse during early childhood in most people, while the frontal sinuses continue developing as the face and skull mature.
By combining strength, carefully shaped surfaces, internal spaces, and connections with neighboring bones, the frontal bone helps the skull protect the brain while supporting the sensory organs and facial structures that make everyday activities possible.