The maxilla (plural: ''maxillae'' ) in
vertebrates
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () (chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with ...
is the upper fixed (not fixed in
Neopterygii
Neopterygii (from Greek νέος ''neos'' 'new' and πτέρυξ ''pteryx'' 'fin') is a subclass of ray-finned fish (Actinopterygii). Neopterygii includes the Holostei and the Teleostei, of which the latter comprise the vast majority of extant ...
)
bone
A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, ...
of the
jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the
hard palate
The hard palate is a thin horizontal bony plate made up of two bones of the facial skeleton, located in the roof of the mouth. The bones are the palatine process of the maxilla and the horizontal plate of palatine bone. The hard palate spans t ...
in the front of the
mouth
In animal anatomy, the mouth, also known as the oral cavity, or in Latin cavum oris, is the opening through which many animals take in food and issue vocal sounds. It is also the cavity lying at the upper end of the alimentary canal, bounded on ...
. The two maxillary bones are fused at the intermaxillary suture, forming the
anterior nasal spine. This is similar to the
mandible
In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...
(lower jaw), which is also a fusion of two mandibular bones at the
mandibular symphysis
In human anatomy, the facial skeleton of the skull the external surface of the mandible is marked in the median line by a faint ridge, indicating the mandibular symphysis (Latin: ''symphysis menti'') or line of junction where the two lateral halve ...
. The mandible is the movable part of the jaw.
Structure
![Sobo 1909 100 - Palatine process of maxilla](https://upload.wikimedia.org/wikipedia/commons/c/c9/Sobo_1909_100_-_Palatine_process_of_maxilla.png)
In humans, the maxilla consists of:
* The body of the maxilla
* Four
processes
A process is a series or set of activities that interact to produce a result; it may occur once-only or be recurrent or periodic.
Things called a process include:
Business and management
*Business process, activities that produce a specific se ...
** the
zygomatic process
** the
frontal process of maxilla
The frontal process of maxilla is a strong plate, which projects upward, medialward, and backward from the maxilla, forming part of the lateral boundary of the nose.
Its ''lateral surface'' is smooth, continuous with the anterior surface of the b ...
** the
alveolar process
The alveolar process () or alveolar bone is the thickened ridge of bone that contains the tooth sockets on the jaw bones (in humans, the maxilla and the mandible). The structures are covered by gums as part of the oral cavity.
The synonymous ...
** the
palatine process
* three surfaces – anterior, posterior, medial
* the
Infraorbital foramen
* the
maxillary sinus
The pyramid-shaped maxillary sinus (or antrum of Highmore) is the largest of the paranasal sinuses, and drains into the middle meatus of the nose through the osteomeatal complex.Human Anatomy, Jacobs, Elsevier, 2008, page 209-210
Structure
It i ...
* the
incisive foramen
In the human mouth, the incisive foramen (also known as: "''anterior palatine foramen''", or "''nasopalatine foramen''") is the opening of the incisive canals on the hard palate immediately behind the incisor teeth. It gives passage to blood ves ...
Articulations
Each maxilla articulates with nine bones:
* two of the
cranium
The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, th ...
: the
frontal
Front may refer to:
Arts, entertainment, and media Films
* ''The Front'' (1943 film), a 1943 Soviet drama film
* ''The Front'', 1976 film
Music
*The Front (band), an American rock band signed to Columbia Records and active in the 1980s and ea ...
and
ethmoid
The ethmoid bone (; from grc, ἡθμός, hēthmós, sieve) is an unpaired bone in the skull that separates the nasal cavity from the brain. It is located at the roof of the nose, between the two orbits. The cubical bone is lightweight due to a ...
* seven of the
face
The face is the front of an animal's head that features the eyes, nose and mouth, and through which animals express many of their emotions. The face is crucial for human identity, and damage such as scarring or developmental deformities may aff ...
: the
nasal
Nasal is an adjective referring to the nose, part of human or animal anatomy. It may also be shorthand for the following uses in combination:
* With reference to the human nose:
** Nasal administration, a method of pharmaceutical drug delivery
* ...
,
zygomatic,
lacrimal,
inferior nasal concha
The inferior nasal concha (inferior turbinated bone or inferior turbinal/turbinate) is one of the three paired nasal conchae in the nose. It extends horizontally along the lateral wall of the nasal cavity and consists of a lamina of spongy bone, c ...
,
palatine
A palatine or palatinus (in Latin; plural ''palatini''; cf. derivative spellings below) is a high-level official attached to imperial or royal courts in Europe since Roman times. ,
vomer
The vomer (; lat, vomer, lit=ploughshare) is one of the unpaired facial bones of the skull. It is located in the midsagittal line, and articulates with the sphenoid, the ethmoid, the left and right palatine bones, and the left and right max ...
, and the adjacent fused maxilla.
Sometimes it articulates with the orbital surface, and sometimes with the
lateral pterygoid plate
The pterygoid processes of the sphenoid (from Greek ''pteryx'', ''pterygos'', "wing"), one on either side, descend perpendicularly from the regions where the body and the greater wings of the sphenoid bone unite.
Each process consists of a me ...
of the
sphenoid.
Development
![Gray162](https://upload.wikimedia.org/wikipedia/commons/9/97/Gray162.png)
The maxilla is ossified in membrane.
Mall
Mall commonly refers to a:
* Shopping mall
* Strip mall
* Pedestrian street
* Esplanade
Mall or MALL may also refer to:
Places Shopping complexes
* The Mall (Sofia) (Tsarigradsko Mall), Sofia, Bulgaria
* The Mall, Patna, Patna, Bihar, India
...
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.
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.
Function
![FracLeftNasalBoneMark](https://upload.wikimedia.org/wikipedia/commons/7/7e/FracLeftNasalBoneMark.png)
The
alveolar process
The alveolar process () or alveolar bone is the thickened ridge of bone that contains the tooth sockets on the jaw bones (in humans, the maxilla and the mandible). The structures are covered by gums as part of the oral cavity.
The synonymous ...
of the maxillae holds the upper teeth, and is referred to as the maxillary arch. Each maxilla attaches laterally to the
zygomatic bone
In the human skull, the zygomatic bone (from grc, ζῠγόν, zugón, yoke), also called cheekbone or malar bone, is a paired irregular bone which articulates with the maxilla, the temporal bone, the sphenoid bone and the frontal bone. It is s ...
s (cheek bones).
Each maxilla assists in forming the boundaries of three cavities:
* the roof of the
mouth
In animal anatomy, the mouth, also known as the oral cavity, or in Latin cavum oris, is the opening through which many animals take in food and issue vocal sounds. It is also the cavity lying at the upper end of the alimentary canal, bounded on ...
* the floor and lateral wall of the
nasal cavity
The nasal cavity is a large, air-filled space above and behind the human nose, nose in the middle of the face. The nasal septum divides the cavity into two cavities, also known as fossae. Each cavity is the continuation of one of the two nostrils. ...
* the wall of the
orbit
In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as ...
Each maxilla also enters into the formation of two fossae: the
infratemporal and
pterygopalatine, and two
fissures
A fissure is a long, narrow crack opening along the surface of Earth. The term is derived from the Latin word , which means 'cleft' or 'crack'. Fissures emerge in Earth's crust, on ice sheets and glaciers, and on volcanoes.
Ground fissure
...
, 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.
Clinical significance
A
maxilla fracture is a form of
facial fracture. A maxilla fracture is often the result of
facial trauma
Facial trauma, also called maxillofacial trauma, is any physical trauma to the face. Facial trauma can involve soft tissue injuries such as burns, lacerations and bruises, or fractures of the facial bones such as nasal fractures and fractures ...
such as
violence
Violence is the use of physical force so as to injure, abuse, damage, or destroy. Other definitions are also used, such as the World Health Organization's definition of violence as "the intentional use of physical force or power, threatened ...
,
falls or
automobile accidents. Maxilla fractures are classified according to the
Le Fort classification.
In other animals
Sometimes (e.g. in bony fish), the maxilla is called "upper maxilla", with the mandible being the "lower maxilla". Conversely, in birds the upper jaw is often called "upper mandible".
In most vertebrates, the foremost part of the upper jaw, to which the
incisor
Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wher ...
s are attached in mammals consists of a separate pair of bones, the
premaxilla
The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has ...
e. These fuse with the maxilla proper to form the bone found in humans, and some other mammals. In
bony fish,
amphibians, and
reptiles, both maxilla and premaxilla are relatively plate-like bones, forming only the sides of the upper jaw, and part of the face, with the premaxilla also forming the lower boundary of the
nostril
A nostril (or naris , plural ''nares'' ) is either of the two orifices of the nose. They enable the entry and exit of air and other gasses through the nasal cavities. In birds and mammals, they contain branched bones or cartilages called turbi ...
s. However, in mammals, the bones have curved inward, creating the palatine process and thereby also forming part of the roof of the mouth.
Bird
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...
s do not have a maxilla in the strict sense; the corresponding part of their
beak
The beak, bill, or rostrum is an external anatomical structure found mostly in birds, but also in turtles, non-avian dinosaurs and a few mammals. A beak is used for eating, preening, manipulating objects, killing prey, fighting, probing for foo ...
s (mainly consisting of the premaxilla) is called "upper mandible".
Cartilaginous fish, such as sharks, also lack a true maxilla. Their upper jaw is instead formed from a
cartilaginous
Cartilage is a resilient and smooth type of connective tissue. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck a ...
bar that is not
homologous with the bone found in other vertebrates.
[
]
Additional images
File:Maxilla anterior.png, Skull. Maxilla shown in green.
Maxilla - animation 02.gif, Skull. Maxilla shown in white.
See also
* Maxillofacial surgery
*Maxillary crest
The nasal septum () separates the left and right airways of the nasal cavity, dividing the two nostrils.
It is depressed by the depressor septi nasi muscle.
Structure
The fleshy external end of the nasal septum is called the columella or co ...
References
Further reading
*
*
External links
*
{{Authority control
Bones of the head and neck
Dental anatomy
Irregular bones
Human mouth anatomy