The maxilla is a structural component of the human face, commonly known as the upper jaw bone. There are two maxilla bones, a pair of symmetrical bones that join together at the midline of the face. These paired bones are foundational to the mid-face, providing the primary support for the upper teeth and shaping the central facial contour. They function as a single unit in the adult skull, though they originate as two distinct bones during development.
Structure and Location
The maxilla bones are centrally located in the facial skeleton, forming the middle third of the face. Each bone has a roughly pyramidal shape, consisting of a central body and four distinct processes that articulate with other facial and cranial bones. The largest feature within the body is the maxillary sinus, the most voluminous of the paranasal sinuses.
The four processes anchor the maxilla to the rest of the skull:
- The frontal process extends upward toward the forehead to meet the frontal bone.
- The zygomatic process projects laterally to connect with the cheekbone.
- The palatine process is a thick, horizontal shelf that extends medially to form the majority of the hard palate, the roof of the mouth.
- The alveolar process is the horseshoe-shaped structure that houses the sockets for the upper teeth.
The maxillary sinus is an air-filled cavity occupying a significant portion of the maxilla’s interior, extending from above the molar and premolar teeth toward the eye socket floor. This large sinus lightens the weight of the skull and contributes to voice resonance. The medial walls of the two maxillae join together at the intermaxillary suture.
Essential Roles of the Maxilla
The maxilla performs several functions necessary for daily life. Its most obvious role is to anchor the upper row of teeth within the alveolar process, which is necessary for mastication (chewing). Although the lower jaw (mandible) provides all the movement, the maxilla provides the stable platform against which the lower teeth grind food.
The maxilla also forms three major cavities within the skull. The palatine process creates approximately two-thirds of the hard palate, separating the oral cavity from the nasal cavity. This separation is important for both eating and breathing. The maxilla also forms the floor of the nasal cavity and contributes to the floor of the eye socket (orbit).
The robust structure and connections of the maxilla help to absorb and dissipate forces from facial impacts, protecting delicate structures like the eyes and brain. The large maxillary sinus also influences the quality and pitch of the voice by acting as a resonating chamber.
Common Injuries
Because of its central and exposed position in the mid-face, the maxilla is susceptible to traumatic injury. Common causes of fracture include high-energy blunt force trauma, such as motor vehicle accidents, physical altercations, and severe falls. Maxillary fractures account for a significant percentage of all facial bone injuries.
Maxillary fractures are classified using the Le Fort system, a standardized grouping based on predictable lines of weakness within the mid-face. These classifications describe the horizontal, pyramidal, or transverse pattern of separation of the maxilla from the rest of the skull. A Le Fort I fracture, for example, is a horizontal break separating the tooth-bearing segment from the main body.
Maxillary trauma often requires surgical intervention because displaced fragments can impair breathing, disrupt the ability to chew, and affect eye function. Such injuries may also cause numbness in the cheek or lip due to nerve involvement. Careful repair is necessary to restore the structural integrity and functional alignment of the mid-face.