The frontal bone, one of the bones that form the skull in the human skeletal system, constitutes a large part of the forehead and the upper part of the eye sockets. This bone, whose Latin name is os frontale, is bipartite during the embryonic period and fuses into a single piece after birth. Among the skull bones, it plays an important role both protectively and structurally. The frontal bone, which surrounds and supports the frontal lobe of the brain, also functions as an attachment point for muscles that affect facial expression.
Anatomical Structure and Features
The frontal bone belongs to the group of flat bones and forms the antero-superior part of the skull. Anatomically, it is associated with the forehead, glabella, superior orbital margin, and the root of the nose. While the anterior surface of the bone lies beneath the superficial muscles and skin, its posterior surface is adjacent to the brain tissue.
Parts
The frontal bone is examined in three main parts.
Squama frontalis
It is a wide, flat structure corresponding to the forehead region. On its external surface, two frontal eminences (eminentia frontalis), the glabella, and the superciliary arches are located. On its internal surface, areas where the frontal sinuses begin, and impressions and elevations bearing the marks of the frontal lobes of the brain are observed.
Pars orbitalis
It is the region located on the inferior surface of the frontal bone and forming the upper part of the orbit. This structure consists of two flat plates and contains the ethmoidal notch (incisura ethmoidalis) between them. This notch allows for the placement of the ethmoid bone. The pars orbitalis also provides a protective structure for the eyeball, eye muscles, and neurovascular structures.
Pars nasalis
It is a narrow part that joins the root of the nose. It connects with the nasal bones and the maxillary bones. This section plays an important role in the articulations of the frontal bone with other cranial bones.
Articulations
The frontal bone articulates with various bones depending on its position within the skull:
- It joins with the parietal bones along the coronal suture.
- with the nasal bones at the root of the nose,
- with the maxillary and lacrimal bones in the medial wall of the orbit,
- with the sphenoid bone at its base,
- and with the ethmoid bone in the medial part of the orbit.
These joints are immovable fibrous joints (suture type).
Development and Ossification
The development of the frontal bone begins in the embryonic period and forms as two separate bone pieces. After birth, usually by the end of the second year, these two pieces fuse along the median line to become a single bone. This fusion line is called the metopic suture (sutura metopica). In some individuals, this suture may persist into adulthood.
The ossification of the frontal bone occurs via intramembranous ossification. In this process, mesenchymal cells directly transform into bone tissue.
Clinical Significance
The frontal bone is an area susceptible to trauma. Especially blows to the forehead region can cause cracks or fractures in the bone. Furthermore, infections developing in the frontal sinuses (frontal sinusitis) can manifest with symptoms such as headache and nasal congestion.
Frontal Sinuses
Inside the frontal bone, there are two frontal sinuses, one on the right and one on the left. These cavities are connected to the nasal cavity and provide resonance for the voice. The size of the sinuses can vary from person to person. Frontal sinuses generally begin to become prominent after the age of 6 and complete their full development during adolescence.
