Frontal bone

The frontal bone, one of the bones that make up the skull in the human skeletal system, forms a large part of the forehead and the upper part of the eye sockets. This bone, whose Latin name is os frontale , is double-structured in the embryonic period and fuses after birth to become a single piece. It plays an important role among the bones of the skull, both in terms of protection and structure. The frontal bone, which surrounds and supports the frontal lobe of the brain, also serves as the attachment point for the muscles that affect facial expression.

Anatomical Structure and Features

The frontal bone is included in the group of flat bones and forms the anterior upper part of the skull. Anatomically, it is related to the forehead, glabella, upper rim of the orbit, and root of the nose. The anterior surface of the bone is under the superficial muscles and skin, while the posterior surface is adjacent to the brain tissue.

Parts of the Frontal Bone

The frontal bone is examined in three main parts.

Frontal squama

It is a wide, flat structure corresponding to the forehead region. On its outer surface, there are two frontal prominences (eminentia frontalis), the glabella and the eyebrow arches, called superciliary arches. On its inner surface, the regions where the frontal sinuses begin and the indentations and protrusions bearing the traces of the frontal lobes of the brain are observed.

Pars orbitalis

It is the region located on the lower surface of the frontal bone and forms the upper part of the orbit. This structure consists of two flat plates and contains the ethmoid notch (incisura ethmoidalis) between them. This notch allows the ethmoid bone to be placed. The pars orbitalis also provides a protective structure for the eyeball, eye muscles and vascular-nerve structures.

Pars nasalis

It is a narrow part that connects to the root of the nose. It connects to the nasal bones and maxillary bones. This part 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 location within the skull:

• It articulates with the parietal bones along the coronal suture.
• At the root of the nose with the nasal bones,
• Maxillary and lacrimal bones and the medial wall of the orbit,
• At the base of the sphenoid bone,
• It articulates with the ethmoid bone in the medial part of the orbit.

These joints are fibrous joints (sutura type) that do not have the ability to move.

Development and Ossification

The development of the frontal bone begins in the embryonic period and is formed as two separate bone parts. After birth, usually by the end of the second year, these two parts fuse along the median line to become a single bone. This junction line is called the metopic suture (sutura metopica). In some individuals, this suture may persist into adulthood.

Ossification of the frontal bone occurs through intramembranous ossification, a process in which mesenchymal cells directly transform into bone tissue.

Clinical Significance

The frontal bone is an area vulnerable to trauma. Blows, especially to the forehead, can cause cracks or fractures in the bone. In addition, infections in the frontal sinuses (frontal sinusitis) can present with symptoms such as headache and nasal congestion.

Frontal Sinuses

There are two frontal sinuses, right and left, inside the frontal bone. These cavities are connected to the nasal cavity and provide resonance of the voice. The size of the sinuses can vary from person to person. The frontal sinuses usually begin to become apparent after the age of 6 and complete their full development in adolescence.