The facial skeleton comprises the ''facial bones'' that may attach to build a portion of the skull. The remainder of the skull is the neurocranium. In human anatomy and development, the facial skeleton is sometimes called the ''membranous viscerocranium'', which comprises the

mandible In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...

and dermatocranial elements that are not part of the braincase.

Structure

In the human skull, the facial skeleton consists of fourteen bones in the face: * Inferior turbinal (2) * Lacrimal bones (2) *

Mandible In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...

Maxilla In vertebrates, the maxilla (: maxillae ) 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 maxil ...

(2) * Nasal bones (2) * Palatine bones (2) *

Vomer The vomer (; ) 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 maxillary bones. The vomer forms ...

* Zygomatic bones (2)

Variations

Elements of the ''cartilaginous viscerocranium'' (i.e., splanchnocranial elements), such as the hyoid bone, are sometimes considered part of the facial skeleton. The

ethmoid bone The ethmoid bone (; from ) 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 (cube-shaped) bone is lightweight due to a spongy constructi ...

(or a part of it) and also 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 occipital bone, basilar part of the occipital bone. The sphenoid bone is one of the seven bon ...

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 The neural crest is a ridge-like structure that is formed transiently between the epidermal ectoderm and neural plate during vertebrate development. Neural crest cells originate from this structure through the epithelial-mesenchymal transition, ...

cells (also responsible for the development of the neurocranium, teeth and adrenal medulla) or from the sclerotome, which derives from the somite block of the

mesoderm The mesoderm is the middle layer of the three germ layers that develops during gastrulation in the very early development of the embryo of most animals. The outer layer is the ectoderm, and the inner layer is the endoderm.Langman's Medical ...

. As with the neurocranium, in Chondricthyes 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, RUNX2, GLI3, PAX1 and

PAX3 The PAX3 (paired box gene 3) gene encodes a member of the paired box or Pax genes, PAX family of transcription factors. The PAX family consists of nine human (PAX1-PAX9) and nine mouse (Pax1-Pax9) members arranged into four subfamilies. Human PAX ...

were found to determine nasal morphology, whereas EDAR 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.

References

External links