A maxilla is one of a pair of bones that forms the upper jaw of the skull. At their base the maxillae carry
the upper teeth and form the roof of the mouth.
At the top, the maxillae form the floor of the orbits (sockets) of the eyes.
Each maxilla contains a large air-filled cavity, called the maxillary
sinus, which is connected to the nasal cavity. The two bones meet at
the intermaxillary suture and form the lower margin of
the nasal aperture. Below the orbit the maxilla is perforated by the infraorbital
foramen. The alveolar process projects downward
and, together with its fellow on the opposite side forms the alveolar
arch, which carries the upper teeth.
Credit: Gray's Anatomy
Incomplete fusion of the maxillae leads to cleft
palate and hairlip.