The maxilla is a paired bone of the skull that contains an air-filled cavity called the maxillary sinus. This bone is a part of the viscerocranium of the skull.

Both maxillary bones (maxillae) are fused in the midline by the intermaxillary suture to form the upper jaw. The fusion of both maxillae creates a projection called the anterior nasal spine, which is the anterior point of the upper jaw that serves as a cephalometric landmark.

Each maxilla has five parts, including the central body of the maxilla and four processes:

• Frontal process
• Zygomatic process
• Palatine process
• Alveolar process

Body of maxilla

The body is the central portion of the maxilla. It houses the maxillary sinus and supports all four processes.

The maxillary body has four surfaces: anterior, orbital, nasal and infratemporal. 

• The anterior surface features the following landmarks:
  • Nasal notch - located on the medial margin close to the anterior nasal spine;
  • Infraorbital margin - forms the inferior margin of the orbit;
  • Infraorbital foramen - situated below the middle part of the infraorbital margin;
  • Canine fossa - located inferior to the infraorbital foramen.
• The orbital surface is the superior surface of the body. It forms most of the orbital floor and features the infraorbital groove that leads into the infraorbital canal.
• The nasal surface forms a part of the lateral wall of the nasal cavity and features a large opening called the maxillary hiatus that leads into the maxillary sinus.
• The infratemporal surface is the posterior surface of the maxilla. It presents the maxillary tuberosity that contains small openings called the alveolar foramina. The alveolar foramina lead into the alveolar canals.

Frontal process

The frontal process is the superior extension of the maxilla. It projects upward, medially and slightly backward and articulates with the frontal bone.

This process features the lacrimal groove - a vertical groove located on the posterior aspect of it. 

Zygomatic process

The zygomatic process is the short lateral extension of the maxilla for articulation with the zygomatic bone.

Palatine process

The palatine process is the medial extension of the maxilla. It is shaped like a horizontal plate and forms the largest part of the hard palate. 

It features the opening of the incisive canal named the incisive foramen that can be found on the anterior part of the process.

Alveolar process

The alveolar process is an inferior crested extension of the maxilla. Like the alveolar process of the mandible, it also houses the teeth. 

The curved free margin of the alveolar process is called the alveolar arch. The alveolar arch of the maxilla (as the alveolar arch of the mandible) features the following landmarks:

• Dental alveoli - sockets in the alveolar process in which lie the roots of the teeth;
• Interalveolar septa - bony ridges between adjacent dental alveoli;
• Interradicular septa - bony ridges forming compartments in dental alveoli for the roots of the teeth;
• Alveolar yokes (juga alveolaria) - eminences on the outer surface of the alveolar arch produced by the projections of the dental alveoli.

Sutures

Besides the intermaxillary suture between both fused maxillary bones, the maxillae have two or three more sutures. All of them are located in the palatine process, and two of the sutures form the hard palate. 

• The first suture is a sagittal-oriented median palatine suture that connects both maxillae and horizontal plates of the palatine bones as it extends from the maxillae to the palatine bones. 
• The next suture is a horizontal-oriented transverse palatine suture that separates the palatine processes of the maxillae from the horizontal plates of the palatine bones.
• The third suture - the incisive suture - is not always present. It is situated on the anterior portion of the palatine processes, and it separates the anterior parts of the maxillae, which contain dental alveoli, from the rest of the palatine processes.