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In the
human skull 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 zygomatic bone (from grc, ζῠγόν, zugón, yoke), also called cheekbone or malar bone, is a paired
irregular bone The irregular bones are bones which, from their peculiar form, cannot be grouped as long, short, flat or sesamoid bones. Irregular bones serve various purposes in the body, such as protection of nervous tissue (such as the vertebrae protect the ...
which articulates with 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 t ...
, the
temporal bone The temporal bones are situated at the sides and base of the skull, and lateral to the temporal lobes of the cerebral cortex. The temporal bones are overlaid by the sides of the head known as the temples, and house the structures of the ears. T ...
, the
sphenoid bone The sphenoid bone is an unpaired bone of the neurocranium. It is situated in the middle of the skull towards the front, in front of the basilar part of the occipital bone. The sphenoid bone is one of the seven bones that articulate to form the o ...
and the
frontal bone The frontal bone is a bone in the human skull. The bone consists of two portions.''Gray's Anatomy'' (1918) These are the vertically oriented squamous part, and the horizontally oriented orbital part, making up the bony part of the forehead, part ...
. It is situated at the upper and lateral part of the face and forms the prominence of the cheek, part of the lateral wall and floor 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 a ...
, and parts of the
temporal fossa The temporal fossa is a fossa (shallow depression) on the side of the skull bounded by the temporal lines and terminating below the level of the zygomatic arch. Boundaries * Medial: frontal bone, parietal bone, temporal bone, and sphenoid ...
and the infratemporal fossa. It presents a malar and a temporal surface; four processes (the frontosphenoidal, orbital, maxillary, and temporal), and four borders.


Etymology

The term ''zygomatic'' derives from the Ancient Greek , ''zygoma'', meaning "yoke". The zygomatic bone is occasionally referred to as the
zygoma The term zygoma generally refers to the zygomatic bone, a bone of the human skull commonly referred to as the cheekbone or malar bone, but it may also refer to: * The zygomatic arch, a structure in the human skull formed primarily by parts of the ...
, but this term may also refer to the
zygomatic arch In anatomy, the zygomatic arch, or cheek bone, is a part of the skull formed by the zygomatic process of the temporal bone (a bone extending forward from the side of the skull, over the opening of the ear) and the temporal process of the zygomat ...
.


Structure


Surfaces

The ''malar surface'' is convex and perforated near its center by a small aperture, the zygomaticofacial foramen, for the passage of the zygomaticofacial nerve and vessels; below this foramen is a slight elevation, which gives origin to the zygomaticus muscle. The ''temporal surface'', directed posteriorly and medially, is concave, presenting medially a rough, triangular area, for articulation with the maxilla (articular surface), and laterally a smooth, concave surface, the upper part of which forms the anterior boundary of the
temporal fossa The temporal fossa is a fossa (shallow depression) on the side of the skull bounded by the temporal lines and terminating below the level of the zygomatic arch. Boundaries * Medial: frontal bone, parietal bone, temporal bone, and sphenoid ...
, the lower a part of the infratemporal fossa. Near the center of this surface is the zygomaticotemporal foramen for the transmission of the
zygomaticotemporal nerve The zygomaticotemporal nerve (zygomaticotemporal branch, temporal branch) is a small nerve of the face. It is derived from the zygomatic nerve, a branch of the maxillary nerve (CN V2). It is distributed to the skin of the side of the forehead. It ...
. The ''orbital surface'' forms the lateral part and some of the inferior part of the bony orbit. The
zygomatic nerve The zygomatic nerve is a branch of the maxillary nerve, itself a branch of the trigeminal nerve (CN V). It travels through the orbit and divides into the zygomaticotemporal and the zygomaticofacial nerve. It provides sensory supply to skin ove ...
passes through the zygomatic-orbital foramen on this surface. The lateral palpebral ligament attaches to a small protuberance called the orbital tubercle.


Processes

Each zygomatic bone is diamond-shaped and composed of three processes with similarly named associated bony articulations: frontal, temporal, and maxillary. Each process of the zygomatic bone forms important structures of the skull. The orbital surface of the frontal process of the zygomatic bone forms the anterior lateral orbital wall, with usually a small paired foramen, the zygomaticofacial foramen opening on its lateral surface. The temporal process of the zygomatic bone forms the zygomatic arch along with the zygomatic process of the temporal bone, with a paired zygomaticotemporal foramen present on the medial deep surface of the bone. The orbital surface of the maxillary process of the zygomatic bone forms a part of the infraorbital rim and a small part of the anterior part of the lateral orbital wall.


Orbital process

The orbital process is a thick, strong plate, projecting backward and medialward from the orbital margin. Its ''antero-medial surface'' forms, by its junction with the orbital surface 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 t ...
and with the great wing of the sphenoid, part of the floor and lateral wall of the orbit. On it are seen the orifices of two canals, the zygomatico-orbital foramina; one of these canals opens into the
temporal fossa The temporal fossa is a fossa (shallow depression) on the side of the skull bounded by the temporal lines and terminating below the level of the zygomatic arch. Boundaries * Medial: frontal bone, parietal bone, temporal bone, and sphenoid ...
, the other on the malar surface of the bone; the former transmits the
zygomaticotemporal The zygomaticotemporal nerve (zygomaticotemporal branch, temporal branch) is a small nerve of the face. It is derived from the zygomatic nerve, a branch of the maxillary nerve (CN V2). It is distributed to the skin of the side of the forehead. It ...
, the latter the
zygomaticofacial nerve The zygomaticofacial nerve or zygomaticofacial branch of zygomatic nerve (malar branch) passes along the infero-lateral angle of the orbit, emerges upon the face through the zygomaticofacial foramen in the zygomatic bone, and, perforating the orb ...
. * Its ''postero-lateral surface,'' smooth and convex, forms parts of the temporal and infratemporal fossae. * Its ''anterior margin,'' smooth and rounded, is part of the circumference of the orbit. * Its ''superior'' ''margin,'' rough, and directed horizontally, articulates with the frontal bone behind the zygomatic process. * Its ''posterior margin'' is serrated for articulation, with the great wing of the sphenoid and the orbital surface of the maxilla. At the angle of junction of the sphenoidal and maxillary portions, a short, concave, non-articular part is generally seen; this forms the anterior boundary of the inferior orbital fissure: occasionally, this non-articular part is absent, the fissure then being completed by the junction of the maxilla and sphenoid, or by the interposition of a small sutural bone in the angular interval between them.


Borders

The ''antero-superior'' or ''orbital'' border is smooth, concave, and forms a considerable part of the circumference of the orbit. The ''antero-inferior'' or ''maxillary'' border is rough, and bevelled at the expense of its inner table, to articulate with the maxilla; near the orbital margin it gives origin to the
quadratus labii superioris The levator labii superioris (pl. ''levatores labii superioris'', also called quadratus labii superioris, pl. ''quadrati labii superioris'') is a muscle of the human body used in facial expression. It is a broad sheet, the origin of which extends ...
. The ''postero-superior'' or ''temporal'' border, curved like an italic letter ''f,'' is continuous above with the commencement of the temporal line, and below with the upper border of the
zygomatic arch In anatomy, the zygomatic arch, or cheek bone, is a part of the skull formed by the zygomatic process of the temporal bone (a bone extending forward from the side of the skull, over the opening of the ear) and the temporal process of the zygomat ...
; the temporal fascia is attached to it. The ''postero-inferior'' or ''zygomatic border'' affords attachment by its rough edge to the
masseter In human anatomy, the masseter is one of the muscles of mastication. Found only in mammals, it is particularly powerful in herbivores to facilitate chewing of plant matter. The most obvious muscle of mastication is the masseter muscle, since it ...
.


Articulations

The zygomatic bone articulates with the
frontal bone The frontal bone is a bone in the human skull. The bone consists of two portions.''Gray's Anatomy'' (1918) These are the vertically oriented squamous part, and the horizontally oriented orbital part, making up the bony part of the forehead, part ...
,
sphenoid bone The sphenoid bone is an unpaired bone of the neurocranium. It is situated in the middle of the skull towards the front, in front of the basilar part of the occipital bone. The sphenoid bone is one of the seven bones that articulate to form the o ...
, and paired
temporal bone The temporal bones are situated at the sides and base of the skull, and lateral to the temporal lobes of the cerebral cortex. The temporal bones are overlaid by the sides of the head known as the temples, and house the structures of the ears. T ...
s, and maxillary bones.


Development

The zygomatic bone is generally described as ossifying from three centers—one for the malar and two for the orbital portion; these appear about the eighth week and fuse about the fifth month of fetal life. Mall describes it as being ossified from one center which appears just beneath and to the lateral side of the orbit. After birth, the bone is sometimes divided by a horizontal suture into an upper larger, and a lower smaller division. In some
quadrumana Quadrumana is an outdated taxonomic division within the primates. The division of "Quadrumana" from "Bimana" was an attempt at distinguishing ''Homo sapiens'' from the rest of the great apes. For a century, modern science has considered humans as ...
the zygomatic bone consisted of two parts, an orbital and a malar.


Society and culture

Zygomatic arches, also known as high cheek bones, are considered physically attractive in some cultures, in both males and females. Ancient Chinese sculptures of goddesses typically have a "broad forehead, raised
eyebrows An eyebrow is an area of short hairs above each Human eye, eye that follows the shape of the lower margin of the Supraorbital ridge, brow ridges of some mammals. In humans, eyebrows serve two main functions: first, human communication, communica ...
, high cheekbones, and large, sensuous mouth". Similarly, many depictions of Qin warriors in the
Terracotta Army The Terracotta Army is a collection of terracotta sculptures depicting the armies of Qin Shi Huang, the first emperor of China. It is a form of funerary art buried with the emperor in 210–209 BCE with the purpose of protecting the emperor in ...
are depicted with "broad
forehead In human anatomy, the forehead is an area of the head bounded by three features, two of the skull and one of the scalp. The top of the forehead is marked by the hairline, the edge of the area where hair on the scalp grows. The bottom of the fore ...
s, high cheekbones, large eyes, thick eyebrows, and stiff beards." For this reason some individuals undergo cheek augmentation, a form of
cosmetic surgery Plastic surgery is a surgical specialty involving the restoration, reconstruction or alteration of the human body. It can be divided into two main categories: reconstructive surgery and cosmetic surgery. Reconstructive surgery includes craniof ...
.


Other animals

The zygomatic is homologous to the
jugal The jugal is a skull bone found in most reptiles, amphibians and birds. In mammals, the jugal is often called the malar or zygomatic. It is connected to the quadratojugal and maxilla, as well as other bones, which may vary by species. Anatomy ...
bone of other
tetrapods Tetrapods (; ) are four-limb (anatomy), limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant taxon, extant and extinct amphibians, sauropsids (reptiles, including dinosaurs and therefore birds) and synapsids (p ...
.


Non-mammalian vertebrates

In non-
mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...
ian vertebrates, the zygomatic bone is referred to as the
jugal The jugal is a skull bone found in most reptiles, amphibians and birds. In mammals, the jugal is often called the malar or zygomatic. It is connected to the quadratojugal and maxilla, as well as other bones, which may vary by species. Anatomy ...
bone, since these animals have no zygomatic arch. It is found in most
reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates ( lizards and snakes) and rhynchoce ...
s,
amphibian Amphibians are four-limbed and ectothermic vertebrates of the class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arborea ...
s, and birds. It is connected to the
quadratojugal The quadratojugal is a skull bone present in many vertebrates, including some living reptiles and amphibians. Anatomy and function In animals with a quadratojugal bone, it is typically found connected to the jugal (cheek) bone from the front and ...
and
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 t ...
, as well as other bones, which may vary by species. This bone is considered key in the determination of general traits of the skull, as in the case of creatures, such as
dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23  million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is ...
s in
paleontology Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of foss ...
, whose entire skull has not been found. In
coelacanth The coelacanths ( ) are fish belonging to the order Actinistia that includes two extant species in the genus ''Latimeria'': the West Indian Ocean coelacanth (''Latimeria chalumnae''), primarily found near the Comoro Islands off the east coast ...
s and early
tetrapod Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids (reptiles, including dinosaurs and therefore birds) and synapsids (pelycosaurs, extinct therapsid ...
s the bone is relatively large. Here, it is a plate-like bone forming the lower margin of the orbit and much of the side of the face. In
ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or h ...
es it is reduced or absent, and the entire cheek region is generally small. The bone is also absent in living
amphibian Amphibians are four-limbed and ectothermic vertebrates of the class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arborea ...
s. With the exception of
turtle Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked t ...
s, the jugal bone in
reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates ( lizards and snakes) and rhynchoce ...
s forms a relatively narrow bar separating the orbit from the inferior
temporal fenestra An infratemporal fenestra, also called the lateral temporal fenestra or simply temporal fenestra, is an opening in the skull behind the orbit in some animals. It is ventrally bordered by a zygomatic arch. An opening in front of the eye sockets, ...
, of which it may also form the lower boundary. The bone is similarly reduced in birds. In mammals, it takes on broadly the form seen in humans, with the bar between the orbit and fenestra vanishing entirely, and only the lower boundary of the fenestra remaining, as the zygomatic arch.


Additional images


See also

*
Treacher Collins syndrome Treacher Collins syndrome (TCS) is a genetic disorder characterized by deformities of the ears, eyes, cheekbones, and chin. The degree to which a person is affected, however, may vary from mild to severe. Complications may include breathing prob ...
*
Zygoma fracture A zygoma fracture (zygomatic fracture) is a form of facial fracture caused by a fracture of the zygomatic bone. A zygoma fracture is often the result of facial trauma such as violence, falls or automobile accidents. Symptoms include flattening ...
*
Zygomatic arch In anatomy, the zygomatic arch, or cheek bone, is a part of the skull formed by the zygomatic process of the temporal bone (a bone extending forward from the side of the skull, over the opening of the ear) and the temporal process of the zygomat ...
* Zygomatic complex fracture * Zygomatic fossa


References


External links

* {{Authority control Bones of the head and neck Facial features Irregular bones Vertebrate anatomy