The Maxillæ (Upper Jaw)

Anatomy > Gray's Anatomy of the Human Body > II. [Osteology]] > 5b. The Facial Bones. 2. The Maxillae

Henry Gray (1821–1865). Anatomy of the Human Body. 1918.

The Maxilla

The maxilla (plural: maxillae

) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. The upper jaw includes the hard palate in the front of the mouth. 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.

Structure

File:Sobo 1909 100 - Palatine process of maxilla.png

Inferior surface of maxilla

In humans, the maxilla consists of:

• The body of the maxilla
• Four processes
  • The zygomatic process
  • The frontal process of maxilla
  • The alveolar process
  • The palatine process
• Three surfaces - anterior, posterior, medial
• The Infraorbital foramen
• The maxillary sinus
• The incisive foramen

Articulations

Each maxilla articulates with nine bones:

• two of the cranium: the frontal and ethmoid
• seven of the face: the nasal, zygomatic, lacrimal, inferior nasal concha, palatine, vomer, and the adjacent fused maxilla.

Sometimes it articulates with the orbital surface, and sometimes with the lateral pterygoid plate of the sphenoid.

Development

File:Gray161.png

Figure 5: Anterior surface of maxilla at birth.

File:Gray162.png

Figure 6: Inferior surface of maxilla at birth.

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.,

• one, the orbitonasal, forms that portion of the body of the bone which lies medial to the infraorbital canal, including the medial part of the floor of the orbit and the lateral wall of the nasal cavity;
• a second, the zygomatic, gives origin to the portion which lies lateral to the infraorbital canal, including the zygomatic process;
• from a third, the palatine, is developed the palatine process posterior to the incisive canal together with the adjoining part of the nasal wall;
• a fourth, the premaxillary, forms the incisive bone which carries the incisor teeth and corresponds to the premaxilla of the lower vertebrates;
• a fifth, the nasal, gives rise to the frontal process and the portion above the canine tooth;
• and a sixth, the infravomerine, lies between the palatine and premaxillary centers and beneath the vomer; this center, together with the corresponding center of the opposite bone, separates the incisive canals from each other.

Function

File:FracLeftNasalBoneMark.png

Fracture of the left lacrimal / maxillary bone

The alveolar process of the maxillae holds the upper teeth, and is referred to as the maxillary arch. Each maxilla attaches laterally to the zygomatic bones (cheek bones).

Each maxilla assists in forming the boundaries of three cavities:

• the roof of the mouth
• the floor and lateral wall of the nasal cavity
• the wall of the orbit

Each maxilla also enters into the formation of two fossae: the infratemporal and pterygopalatine, and two fissures, the inferior orbital and pterygomaxillary. -When the tender bones of the upper jaw and lower nostril are severely or repetitively damaged, at any age the surrounding cartilage can begin to deteriorate just as it does after death. ^{(January 2016)}

Additional images

• Skull. Maxilla shown in green.
  Skull. Maxilla shown in green.

External links

• Anatomy photo:22:os-1901 at the SUNY Downstate Medical Center

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