Editing Maxilla (section)

==Anatomy==

=== Structure ===
The maxilla is a paired bone - the two maxillae unite with each other at the intermaxillary suture. The maxilla consists of:<ref name=":0">{{Cite book |last=Fehrenbach |first=Margaret J. |title=Illustrated Anatomy of the Head and Neck |last2=Herring |first2=Susan W. |date=2017 |publisher=Elsevier |isbn=978-0-323-39634-9 |edition=5th |location=St. Louis |pages=61}}</ref>[[File:Sobo 1909 100 - Palatine process of maxilla.png|thumb|right|Inferior surface of maxilla]]
* The '''body of the maxilla''': pyramid-shaped; has an orbital, a nasal, an infratemporal, and a facial surface; contains the [[maxillary sinus]].
* Four [[Process (anatomy)|processes]]:
** the [[Zygomatic process of maxilla|zygomatic process]]
** the [[frontal process of maxilla|frontal process]]
** the [[alveolar process]]
** the [[palatine process]]
It has three surfaces:<ref name=":0" />
* the anterior, posterior, medial
Features of the maxilla include:<ref name=":0" />
* the [[Infraorbital groove|infraorbital sulcus]], [[Infraorbital canal|canal]], and [[Infraorbital foramen|foramen]]
* the [[maxillary sinus]]
* the [[incisive foramen]]

===Articulations===
Each maxilla articulates with nine bones: [[Frontal bone|frontal]], [[ethmoid]], [[nasal bone|nasal]], [[zygomatic bone|zygomatic]], [[lacrimal bone|lacrimal]], and [[Palatine bone|palatine]] bones, the [[vomer]], the [[inferior nasal concha]], as well as the maxilla of the other side.<ref name=":0" />

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

===Development===
[[File:Gray161.png|thumb|Anterior surface of maxilla at birth]]
[[File:Gray162.png|thumb|Inferior surface of maxilla at birth]]
The maxilla is ossified in membrane. [[Franklin P. Mall|Mall]] and Fawcett maintain that it is ossified from ''two'' centers only, one for the maxilla proper and one for the premaxilla.<ref>{{cite journal |first=Franklin P. |last=Mall |title=On ossification centers in human embryos less than one hundred days old |journal=[[American Journal of Anatomy]] |year=1906 |volume=5 |issue=4 |pages=433–458 |doi=10.1002/aja.1000050403 |url=https://zenodo.org/record/2179571 }}</ref><ref>{{cite journal |first=Edward |last=Fawcett |title=Some Notes on the Epiphyses of the Ribs |journal=[[Journal of Anatomy and Physiology]] |year=1911 |volume= 45 |issue=Pt 2 |pages=172–178 |pmc=1288875 |pmid=17232872 }}</ref>

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.

====Changes by age====
At birth the transverse and antero-posterior diameters of the bone are each greater than the vertical.

The frontal process is well-marked and the body of the bone consists of little more than the alveolar process, the teeth sockets reaching almost to the floor of the orbit.

The maxillary sinus presents the appearance of a furrow on the lateral wall of the nose. In the adult the vertical diameter is the greatest, owing to the development of the alveolar process and the increase in size of the sinus.