Maxilla

  • The maxilla (or upper jaw bone, latin: maxilla) is a paired bone that has a body and four processes: frontal process, zygomatic process, palatine process, and alveolar process. The two maxillary bones (maxillae) are fused in the midline by the intermaxillary suture to form the upper jaw.

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

    • frontal process,
    • zygomatic process,
    • palatine process,
    • alveolar process.

    Body of maxilla

    The body of the maxilla is the central portion of the maxilla housing the maxillary sinus and supporting the four processes of the maxilla. The body of the maxilla has four surfaces: anterior, orbital, nasal, and infratemporal surfaces.

    The anterior surface of the body of the maxilla features the following structures:

    • nasal notch,
    • infra-orbital margin,
    • infra-orbital foramen,
    • canine fossa.

    The nasal notch is a curved margin of the bony anterior nasal aperture located on the anterior surface of the body of the maxilla.

    The infra-orbital margin is the lower margin of the orbit formed partly by the maxilla, and partly by the zygomatic bone.

    The infra-orbital foramen is an opening on the anterior surface of the body of the maxilla located below the infra-orbital margin. It is the outer opening of the infra-orbital canal serving as the passage for the infraorbital nerve, as well as for the infraorbital artery and vein.

    The canine fossa is a depressed area on the anterior surface of the body of the maxilla located below the infra-orbital foramen. The canine fossa is the origin site of the levator angulis oris muscle.

    The orbital surface of the body of the maxilla forms most of the floor of the orbit and features the infra-orbital groove leading into the infra-orbital canal.

    The infra-orbital groove is situated on the orbital surface of the body of the maxilla (on the floor of the orbit) that continues as the infraorbital canal, thus serving as the passage for the infraorbital nerve and blood vessels.

    The infra-orbital canal is a bony passage within the anterior wall of the maxilla starting from the infra-orbital groove and opening on the anterior surface of the body of the maxilla (with the infra-orbital foramen). The infra-orbital canal is the passage for the infraorbital nerve, as well as the infraorbital artery, and veins.

    The nasal surface of the body of the maxilla forms part of the lateral wall of the nasal cavity and features a large defect - the maxillary hiatus.

    The maxillary hiatus is an opening to the maxillary sinus located on the nasal surface of the maxilla.

    The maxillary sinus is a paranasal sinus, an air-filled cavity located within the body of the maxilla, and opens with the maxillary hiatus in the lateral wall of the nasal cavity below the middle nasal concha.

    The infratemporal surface of the body of the maxilla presents the maxillary tuberosity with alveolar foramina that lead into the alveolar canals.

    The maxillary tuberosity (or maxillary eminence) is a rounded eminence at the lower part of the infratemporal surface of the body of the maxilla. The maxillary tuberosity is the origin site for a few fibers of the medial pterygoid muscle.

    The alveolar foramina are several small openings on the infratemporal surface of the body of the maxilla leading into the alveolar canals for the passage of the posterior superior alveolar nerves and blood vessels to the upper teeth.

    The alveolar canals are small bony canals within the body of the maxilla leading to the alveolar foramina for the passage of nerves and blood vessels to the teeth.

    Processes of maxilla

    The frontal process of the maxilla is an extension of the maxilla projecting upward, medially and backward for articulation of the frontal bone. The frontal process of the maxilla features the lacrimal groove.

    The lacrimal groove is a groove for the nasolacrimal duct. Situated on the anterior part of the lateral surface of the lacrimal bone and on the frontal process of the maxilla the lacrimal groove participates in forming the nasolacrimal canal.

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

    The palatine process of the maxilla is an extension of the maxilla shaped as a horizontal plate forming the largest part of the hard palate. The opening of the incisive canal can be found on the palatine process of the maxilla.

    The incisive canal is a bony passage within the palatine process of the maxilla, which originates as a paired canal from the floor of the nasal cavity and unites with the palate in the uniform incisive fossa. From each of the incisive canals ascends the terminal branch of the greater palatine artery, and descends the nasopalatine nerve.

    An alveolar process is a crested process of upper or lower jaw which 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 structures:

    • dental alveoli,
    • interalveolar septa,
    • interradicular septa,
    • alveolar yokes.

    The dental alveoli are sockets in the alveolar process where the roots of the teeth lie. The dental alveoli of the mandible house the roots of the lower teeth, while the dental alveoli of the maxilla - the upper teeth.

    The interalveolar septa are bony ridges between adjacent dental alveoli in the alveolar arches of the upper and lower jaw bones.

    The interradicular septa are bony ridges forming compartments in dental alveoli for the roots of the teeth in both the upper and lower jaw bones.

    The alveolar yokes (juga alveolaria) are eminences on the outer surface of the jaw produced by the projections of the dental alveoli. They can be seen on both the maxilla and the mandible.