The maxilla (: maxillae mækˈsɪliː) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth.Merriam-Webster Online Dictionary. The two maxillary bones are fused at the intermaxillary suture, forming the anterior nasal spine. This is similar to the mandible (lower jaw), which is also a fusion of two mandibular bones at the mandibular symphysis. The mandible is the movable part of the jaw.
The maxilla is a paired bone - the two maxillae unite with each other at the intermaxillary suture. The maxilla consists of:
The body of the maxilla: pyramid-shaped; has an orbital, a nasal, an infratemporal, and a facial surface; contains the maxillary sinus.
Four processes:
the zygomatic process
the frontal process
the alveolar process
the palatine process
It has three surfaces:
the anterior, posterior, medial
Features of the maxilla include:
the infraorbital sulcus, canal, and foramen
the maxillary sinus
the incisive foramen
Each maxilla articulates with nine bones: frontal, ethmoid, nasal, zygomatic, lacrimal, and palatine bones, the vomer, the inferior nasal concha, as well as the maxilla of the other side.
Sometimes it articulates with the orbital surface, and sometimes with the lateral pterygoid plate of the sphenoid.
The maxilla is ossified in membrane. Mall and Fawcett maintain that it is ossified from two centers only, one for the maxilla proper and one for the premaxilla.
These centers appear during the sixth week of prenatal development and unite in the beginning of the third month, but the suture between the two portions persists on the palate until nearly middle life. Mall states that the frontal process is developed from both centers.
The maxillary sinus appears as a shallow groove on the nasal surface of the bone about the fourth month of development, but does not reach its full size until after the second dentition.
The maxilla was formerly described as ossifying from six centers, viz.