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The maxilla (plural: ''maxillae'' ) in
vertebrates Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions as an indiv ...

vertebrates
is the upper fixed (not fixed in
Neopterygii Neopterygii (from Greek νέος ''neos'' 'new' and πτέρυξ ''pteryx'' 'fin') is a Subclass (taxonomy), subclass of ray-finned fish (Actinopterygii). Neopterygii includes the Holostei and the Teleostei, of which the latter comprise the vast m ...
)
bone A bone is a rigid tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North America * ''Triphosa dubit ...

bone
of the
jaw The jaw is any opposable articulated structure at the entrance of the , typically used for grasping and manipulating food. The term ''jaws'' is also broadly applied to the whole of the structures constituting the vault of the mouth and serving t ...

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 The facial skeleton comprises the ''facial bones'' that may attach to build a portion of the skull The skull is a bone A bone is a Stiffness, ri ...
in the front of the
mouth In animal anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is ...

mouth
. The two maxillary bones are fused at the intermaxillary suture, forming the
anterior nasal spine The anterior nasal spine, or anterior nasal spine of maxilla, is a bony projection in the skull that serves as a cephalometric analysis#Cephalometric landmarks, cephalometric landmark. The anterior nasal spine is the projection formed by the fusion ...
. This is similar to the
mandible In anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any ind ...

mandible
(lower jaw), which is also a fusion of two mandibular bones at the
mandibular symphysis In human anatomy, the facial skeleton The facial skeleton comprises the ''facial bones'' that may attach to build a portion of the skull The skull is a bone A bone is a Stiffness, rigid tissue (anatomy), tissue that constitutes part of the ...
. The mandible is the movable part of the jaw.


Structure

In humans, the maxilla consists of: * the
body of 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. In humans, the upper jaw includes the hard palate in the front of the mouth. The two ...
* four
processes A process is a series or set of Action (philosophy), 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 pro ...
** the
zygomatic process 200px, As a comparison, this is how the skull looks with almost all of the zygomatic process removed. The zygomatic processes are three processes (protrusions) from other bone A bone is a Stiffness, rigid tissue (anatomy), tissue that const ...
** the
frontal process of maxilla The frontal process of maxilla is a strong plate, which projects upward, medialward, and backward from the maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone A bone is a Stiffness ...
** the
alveolar process The alveolar process () (also called the alveolar bone) is the thickened ridge of bone A bone is a Stiffness, rigid tissue (anatomy), tissue that constitutes part of the vertebrate skeleton in animals. Bones protect the various organs of the bo ...

alveolar process
** the
palatine process In human anatomy of the mouth, the palatine process of maxilla (palatal process), is a thick, horizontal process of the maxilla. It forms the anterior three quarters of the hard palate, the horizontal plate of the palatine bone making up the rest. ...

palatine process
* three surfaces – anterior, posterior, medial * the
Infraorbital foramen In human anatomy, the infraorbital foramen is an opening in the maxillary bone of the skull The skull is a bone A bone is a Stiffness, rigid tissue (anatomy), tissue that constitutes part of the vertebrate skeleton in animals. Bones protec ...
* the
maxillary sinus The pyramid-shaped maxillary sinus (or antrum''This is a disambiguation page for the biological term. For the 2018 horror movie, see Antrum (film)'' In biology, antrum is a general term for a cavity or chamber, which may have specific meaning in ...
* the
incisive foramen In the human mouth Humans (''Homo sapiens'') are the most populous and widespread species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of bio ...


Articulations

Each maxilla articulates with nine bones: * two of the
cranium The skull is a bone A bone is a Stiffness, rigid tissue (anatomy), tissue that constitutes part of the vertebrate skeleton in animals. Bones protect the various organs of the body, produce red blood cell, red and white blood cells, store mi ...
: the
frontal Front may refer to: Arts, entertainment, and media Films * The Front (1943 film), ''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 activ ...

frontal
and
ethmoid The ethmoid bone (; from Greek ''ethmos'', "sieve") is an unpaired bone A bone is a Stiffness, rigid tissue (anatomy), tissue that constitutes part of the skeleton in most vertebrate animals. Bones protect the various organs of the body, produ ...

ethmoid
* seven of the
face The face is the front of an animal's head that features the eyes Eyes are organs An organ is a group of tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tis ...

face
: the
nasal
nasal
,
zygomatic
zygomatic
,
lacrimal
lacrimal
,
inferior nasal concha The inferior nasal concha (inferior turbinated bone or inferior turbinal/turbinate) is one of the three paired nasal concha In anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the struc ...
,
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 Empire, Roman times.
palatine
,
vomer The vomer () is one of the unpaired facial skeleton, facial bones of the human skull, skull. It is located in the midsagittal line, and Articulation (anatomy), articulates with the sphenoid bone, sphenoid, the ethmoid bone, ethmoid, the left and r ...

vomer
, 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 of sphenoid bone, body and the greater wing of sphenoid bone, greater wings of the sp ...
of the
sphenoid
sphenoid
.


Development

The maxilla is ossified in membrane.
Mall Mall ( or ) may refer to a shopping mall, a strip mall, or a pedestrian street or an esplanade (a long open area where people can walk, which is the original meaning of the word). Mall or MALL may also refer to: Shopping complexes * Shopping 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 Prenatal development () includes the development of the embryo and of the foetus A fetus or foetus (; plural fetuses, feti, foetuses, or foeti) is the unborn offspring that develops from an animal embryo An embryo is the early stage 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

The
alveolar process The alveolar process () (also called the alveolar bone) is the thickened ridge of bone A bone is a Stiffness, rigid tissue (anatomy), tissue that constitutes part of the vertebrate skeleton in animals. Bones protect the various organs of the bo ...

alveolar process
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 skull is a bone A bone is a Stiffness, rigid tissue (anatomy), tissue that constitutes part of the skeleton in most vertebrate animals. Bones protect the various organs of the body, produce red blood cell, red and ...

zygomatic bone
s (cheek bones). Each maxilla assists in forming the boundaries of three cavities: * the roof of the
mouth In animal anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is ...

mouth
* the floor and lateral wall of the
nasal cavity The nasal cavity is a large, air-filled space above and behind the nose A nose is a protuberance in vertebrates that houses the nostrils, or nares, which receive and expel air for Respiration (physiology), respiration alongside the mouth. Beh ...

nasal cavity
* the wall of the
orbit In celestial mechanics, an orbit is the curved trajectory of an physical body, object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an satellite, artificial satellite around an object or po ...
Each maxilla also enters into the formation of two fossae: the infratemporal and
pterygopalatine
pterygopalatine
, and two
fissures {{Unreferenced, date=December 2009 In anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organism In biology, an organism (from Ancient Greek, Greek: ὀργανισ ...
, 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 injury, soft tissue injuries such as burns, lacerations and bruises, or bone fracture, fractures of the facial bones such ...
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 The World Health Organization (WHO) is a specialized agency of the United Nations ...

violence
, 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 A tooth (plural teeth) is a hard, calcified Calcification is the accumulation of calcium salts in a Tissue (biology), body tissue. It normally occurs in the formation of bone ...
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 Standard anatomical terms of location deal unambiguously with the anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study ...
e. These fuse with the maxilla proper to form the bone found in humans, and some other mammals. In
bony fish Osteichthyes (), popularly referred to as the bony fish, is a diverse taxonomic Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may al ...

bony fish
,
amphibian Amphibians are ectothermic, tetrapod vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial animal, ter ...
s, and
reptile Reptiles, as most commonly defined, are the animals in the class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or ...

reptile
s, 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 A nose is a protuberance in vertebrates that houses the nostrils, or nares, which receive and expel air for Respiration (physiology), respiration alongside ...
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 vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With ...

Bird
s do not have a maxilla in the strict sense; the corresponding part of their
beak The beak, bill, and/or rostrum is an external anatomical structure found mostly in birds Birds are a group of warm-blooded vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellu ...

beak
s (mainly consisting of the premaxilla) is called "upper mandible".
Cartilaginous fish Chondrichthyes (; ) is a class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an an ...

Cartilaginous fish
, such as sharks, also lack a true maxilla. Their upper jaw is instead formed from a
cartilaginous Cartilage (cartilaginous tissue) is a resilient and smooth elastic tissue Elastic is a word often used to describe or identify certain types of elastomer An elastomer is a polymer A polymer (; Greek ''wikt:poly-, poly-'', "many" + ''wikt:-m ...

cartilaginous
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 Oral and maxillofacial surgery is a surgical specialty focusing on reconstructive surgery of the face, facial trauma surgery, the oral cavity, head and neck, mouth, and jaws, as well as facial cosmetic surgery. Specialty An oral and maxil ...
*


References


Further reading

* *


External links

* {{Authority control Bones of the head and neck Dental anatomy Irregular bones Human mouth anatomy