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The facial skeleton comprises the ''facial bones'' that may attach to build a portion of the
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 remainder of the skull is the braincase. In human anatomy and development, the facial skeleton is sometimes called the ''membranous viscerocranium'', which comprises 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 ...
and dermatocranial elements that are not part of the braincase.


Structure

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 facial skeleton consists of fourteen bones in the face: * Inferior turbinal (2) * Lacrimal bones (2) *
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 ...
*
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. T ...
(2) *
Nasal bone The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face and by their junction, form the bridge of the upper one third of the nose. Ea ...
s (2) *
Palatine bone In anatomy, the palatine bones () are two irregular bones of the facial skeleton in many animal species, located above the uvula in the throat. Together with the maxillae, they comprise the hard palate. (''Palate'' is derived from the Latin ...
s (2) *
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 ...
* Zygomatic bones (2)


Variations

Elements of the ''cartilaginous viscerocranium'' (i.e., splanchnocranial elements), such as the
hyoid bone The hyoid bone (lingual bone or tongue-bone) () is a horseshoe-shaped bone situated in the anterior midline of the neck between the chin and the thyroid cartilage. At rest, it lies between the base of the mandible and the third cervical verteb ...
, are sometimes considered part of the facial skeleton. The ethmoid bone (or a part of it) and also the sphenoid bone are sometimes included, but otherwise considered part of the neurocranium. Because the maxillary bones are fused, they are often collectively listed as only one bone. The mandible is generally considered separately from the cranium.


Development

The facial skeleton is composed of dermal bone and derived from the neural crest cells (also responsible for the development of the neurocranium,
teeth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, ...
and adrenal medulla) or from the sclerotome, which derives from the somite block of the mesoderm. As with the neurocranium, in
Chondricthyes Chondrichthyes (; ) is a class that contains the cartilaginous fishes that have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fishes'', which have skeletons primarily composed of bone tissue. ...
and other cartilaginous vertebrates, they are not replaced via endochondral ossification. Variation in craniofacial form between humans is largely due to differing patterns of biological inheritance. Cross-analysis of osteological variables and genome-wide SNPs has identified specific genes that control this craniofacial development. Of these genes,
DCHS2 Protein dachsous homolog 2, also known as protocadherin-23 (PCDH23) or cadherin-27 (CDH27), is a protein that in humans is encoded by the ''DCHS2'' gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to de ...
,
RUNX2 Runt-related transcription factor 2 (RUNX2) also known as core-binding factor subunit alpha-1 (CBF-alpha-1) is a protein that in humans is encoded by the ''RUNX2'' gene. RUNX2 is a key transcription factor associated with osteoblast differentia ...
, GLI3, PAX1 and PAX3 were found to determine nasal morphology, whereas
EDAR Ectodysplasin A receptor (EDAR) is a protein that in humans is encoded by the EDAR gene. EDAR is a cell surface receptor for ectodysplasin A which plays an important role in the development of ectodermal tissues such as the skin. It is structura ...
impacts chin protrusion.


Additional images

File:Slide2rome.JPG, Human facial skeleton. Front view. File:705 Lateral View of Skull-01.svg, Human skull. Lateral view. File:703 Parts of Skull-01.jpg, Facial bones and neurocranium (labeled as "Brain case"). File:BodyParts3D Facial skeleton.stl, 3D model. Click to move.


See also

* Axial skeleton *
Appendicular skeleton The appendicular skeleton is the portion of the skeleton of vertebrates consisting of the bones that support the appendages. There are 126 bones. The appendicular skeleton includes the skeletal elements within the limbs, as well as supporting sh ...


References


External links

* - "Facial Bone Anatomy" {{Authority control Bones of the head and neck Facial features Facial bones de:Schädel#Die Knochen des Schädels