Stirnbein

Stirrnbein, in English commonly called the frontal bone (Os frontale), is a major bone of the skull that forms the forehead and the upper part of the eye sockets. It also contributes to the floor of the anterior cranial fossa and houses the frontal sinuses, air-filled cavities that can vary in size between individuals.

The frontal bone consists primarily of two parts: the vertical squama frontalis, which creates the forehead, and the horizontal orbital part (pars orbitalis) that contributes to the roofs of the orbits and to the medial wall of the eye sockets. On the external surface, pronounced brow ridges, the glabella between the eyebrows, and the supraorbital margins are notable features. The supraorbital margin often contains a foramen or notch through which the supraorbital nerve and vessels pass. The internal surface forms part of the anterior cranial fossa and bears markings related to meningeal attachments and blood vessels.

Articulations include the two parietal bones at the coronal suture, the nasal bones and maxillae medially, the zygomatic bones laterally, and the lacrimal, ethmoid, and sphenoid bones at various points. The frontal bone also forms the roof of the orbits via its orbital plates and houses the frontal sinuses, which communicate with the nasal cavity.

Development occurs mainly through intramembranous ossification. In infants, the frontal bones are separated by the metopic suture, which typically fuses in early childhood. Clinically, fractures of the frontal bone can result from trauma and may involve the frontal sinus or the anterior cranial fossa, with potential complications such as sinus infection or dural injury.