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, the neurocranium, also known as the braincase, brainpan, or brain-pan is the upper and back part of the skull, which forms a protective case around the brain. In the human skull, the neurocranium includes the calvaria or skul ...
.
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
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 ...
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
The adrenal medulla ( la, medulla glandulae suprarenalis) is part of the adrenal gland. It is located at the center of the gland, being surrounded by the adrenal cortex. It is the innermost part of the adrenal gland, consisting of chromaffin cell ...
) 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 Emb ...
. 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
Endochondral ossification is one of the two essential processes during fetal development of the mammalian skeletal system by which bone tissue is produced. Unlike intramembranous ossification, the other process by which bone tissue is produced ...
.
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