Osteology of the Skull: Cranial Bones of the Face

The maxillae are paired bones which make up much of the facial skeleton.  The maxilla houses the upper teeth, forms part of the inferior border of the eye orbit, articulates with the zygomatic to form the cheekbone, forms much of the bony palate, and frames the nasal aperture.

The maxilla possesses a body at its center which surrounds the large maxillary sinus, opening towards the medial side.  Emanating from the body are several processes which are named for the bones with which they articulate.  From an anterior view, the frontal process is visible as it projects superiorly and medially to articulate with the frontal bone. The infraorbital foramen, which transmits the infraorbital nerve to the face, is visible at the base of the frontal process just inferior to the orbital margin.  Just inferior to the infraorbital foramen is a depression of variable depth, the canine fossa. The anterior nasal spine is a superiorly projecting, thin process near the midline of the inferior border of the nasal aperture. The zygomatic process is the superiorly positioned lateral projection forming much of the bony cheek as it articulates with the zygomatic bone.  The alveolar process is the inferior projection from the body which contains numerous alveoli, the openings which hold the roots of the teeth.  The canine jugum is a bony ridge running superiorly from the alveolus of the maxillary canine.

In an inferior view, the maxillary teeth are visible in their alveoli.  The palatine process projects medially to form most of the bony palate and to articulate with the palatine bones.  Near the midline where the palatine processes articulate with each other, the palate is pierced by the incisive foramen, just posterior to the incisors.

In superior view, the orbital process is visible as it projects posteriorly from the orbital margin to form the floor of the orbit.  The posterior margin of the orbital plate is marked by the infraorbital groove, which connects with the infraorbital foramen by means of the infraorbital canal.

Siding the Maxillae

Intact maxillae are readily sided.  The frontal process is superior, the zygomatic process is lateral, the nasal aperture is medial, and the occlusal surfaces of the teeth are inferior.  More fragmentary specimens may be more difficult to side, although the presence of alveoli often offers a useful siding tool.

The zygoma are the paired bones on the lateral sides of the face which make up the cheek bones and form the lateral margins of the orbits.  The zygomatic has a body with three processes: the maxillary process, the zygomatic process, and the frontal process.   The posterior surface of the frontal process bears a flattened orbital surface which is marked by the zygomaticoorbital foramen.  The external surface of the body is smooth and unmarked, save for the zygomaticofacial foramen.  The most inferior portion of the body bears a roughened surface for the origin of the masseter muscle.

Siding the Zygomatic

The superiorly projecting frontal process is the longest and narrowest of the processes.  The orbital margin is on the anterior surface of the frontal process.  The roughened origin for the masseter is on the inferior surface of the body.  The zygomatic process is the only process which does not contribute to the orbit; this process projects posteriorly.

The palatines are small, delicate bones which make up the posterior portion of the palate.  They are almost never found in isolation, but rather adhere to the maxilla and sphenoid.  The palatines are often described as L-shaped.  The horizontal portion which makes up the rear of the palate meets the vertical portion at nearly a 90° angle.  The vertical portions projects superiorly to form part of the orbital wall.  The greater palatine foramen and lesser palatine foramen are visible on the horizontal portion.  The greater foramen is located anterior to the lesser foramen.  Because palatines are usually found adhering to fragments of maxilla or sphenoid, there is little use for knowledge of siding isolated palatines.

The inferior nasal conchae are paired bones which project from the lateral wall of the nasal cavity.  In life they are membranous and covered with vessels.  They function to moisten and warm the inspired air in the nasal cavity.  There is little distinctive morphology on the conchae, and they are highly variable in shape.

The nasals are small rectangular paired bones that form the bony part of the bridge of the nose.  They articulate with each other along the midline, with the frontal superiorly, and with the maxilla laterally.  The lateral (exterior) surface of the nasals is pierced by a nasal foramen.  The medial (interior) surface bears a roughened crest near the midline.

Siding the Nasals

The superior border is marked by the denticulate suture with the frontal.  The medial surface where the nasals articulate with each other is straight and smooth.  The lateral (exterior) surface bears the nasal foramen.

The lacrimals are tiny rectangular paired bones that contribute to the medial wall of the eye orbit.  The lacrimals have an orbital surface which is marked by the inferiorly oriented lacrimal groove which is bounded by the lacrimal crest. The nasal surface bears no important anatomical markers.

Siding the Lacrimals

The lacrimal crest sweeps toward anterior, and the lacrimal groove opens superiorly.  The groove and crest are on the medial (orbital) side of the bone.