In
anatomy
Anatomy () is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having its ...
, fibrous joints are
joints connected by
fibrous tissue, consisting mainly of
collagen. These are fixed joints where
bone
A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, an ...
s are united by a layer of white fibrous tissue of varying thickness. In 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, t ...
the joints between the bones are called
sutures. Such immovable joints are also referred to as
synarthroses.
Types
Most fibrous joints are also called "fixed" or "immovable". These joints have no joint cavity and are connected via fibrous connective tissue.
The skull bones are connected by fibrous joints called ''
sutures''.
In
fetal skulls the sutures are wide to allow slight movement during birth. They later become rigid (
synarthrodial).
Some of the
long bones in the body such as the
radius
In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...
and
ulna in the
forearm
The forearm is the region of the upper limb between the elbow and the wrist. The term forearm is used in anatomy to distinguish it from the arm, a word which is most often used to describe the entire appendage of the upper limb, but which in ...
are joined by a ''
syndesmosis'' (along the
interosseous membrane). Syndemoses are slightly moveable (
amphiarthrodial). The
distal tibiofibular joint is another example.
A ''
gomphosis'' is a joint between the root of a
tooth
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, t ...
and the
socket in 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 ...
or
mandible (jawbones).
Sutures
A suture is a type of fibrous joint that is only found in the skull (cranial suture). The bones are bound together by
Sharpey's fibres. A tiny amount of movement is permitted at sutures, which contributes to the
compliance
Compliance can mean:
Healthcare
* Compliance (medicine), a patient's (or doctor's) adherence to a recommended course of treatment
* Compliance (physiology), the tendency of a hollow organ to resist recoil toward its original dimensions (this is a ...
and
elasticity of the skull.
These joints are
synarthroses.
It is normal for many of the bones of the skull to remain unfused at birth. The fusion of the skull's bones before birth is known as
craniosynostosis. The term "
fontanelle
A fontanelle (or fontanel) (colloquially, soft spot) is an anatomical feature of the infant human skull comprising soft membranous gaps ( sutures) between the cranial bones that make up the calvaria of a fetus or an infant. Fontanelles allo ...
" is used to describe the resulting "soft spots". The relative positions of the bones continue to change during the life of the adult (though less rapidly), which can provide useful information in
forensics and
archaeology
Archaeology or archeology is the scientific study of human activity through the recovery and analysis of material culture. The archaeological record consists of Artifact (archaeology), artifacts, architecture, biofact (archaeology), biofacts ...
. In old age, cranial sutures may ossify (turn to bone) completely.
The joints between the teeth and jaws (gomphoses) and the joint between the mandible and the cranium, the
temporomandibular joint, form the only non-sutured joints in the skull.
Types of sutures
*Serrate sutures – similar to a denticulate suture but the interlocking regions are serrated rather than square. Eg: Coronal suture, sagittal Sutures.
*Plane sutures – edges of the bones are flush with each other as in a normal
butt joint. Eg: Internasal suture.
*Limbous sutures – edges are bevelled so the plane of the suture is sloping as in a
mitre joint. Eg: Temporo-parietal suture.
*Schindylesis – formed by two bones fitting into each other similar to a
bridle joint. Eg: Palatomaxillary suture.
*Denticulate sutures – the edges slot into each other as in a
finger joint. Eg: Lambdoid suture.
*
List of sutures
Most sutures are named for the bones they articulate, but some have special names of their own.
Visible from the side
*
Coronal suture – between the
frontal and
parietal bones
*
Lambdoid suture – between the
parietal and
occipital bones and continuous with the occipitomastoid suture
*
Occipitomastoid suture – between the
occipital and
temporal bones and continuous with the lambdoid suture
*
Sphenofrontal suture
*
Sphenoparietal suture
*
Sphenosquamosal suture
*
Sphenozygomatic suture
*
Squamosal suture – between the parietal and 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 ...
*
Zygomaticotemporal suture
*
Zygomaticofrontal suture
Visible from the front or above
*
Frontal suture /
Metopic suture
The frontal suture is a fibrous joint that divides the two halves of the frontal bone of the skull in infants and children. Typically, it completely fuses between three and nine months of age, with the two halves of the frontal bone being fused t ...
– between the two
frontal bones, prior to the fusion of the two into a single bone
*
Sagittal suture – along the midline, between
parietal bones
Visible from below or inside
*
Frontoethmoidal suture
*
Petrosquamous suture
*
Sphenoethmoidal suture
*
Sphenopetrosal suture
The sphenopetrosal fissure (or sphenopetrosal suture) is the cranial suture between 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 ...
Gallery
File:Lambdoid suture.png, Lambdoid suture
File:SchaedelSeitlichSutur1.png, Coronal suture
File:SchaedelSeitlichSutur3.png, Squamosal suture
File:SchaedelSeitlichSutur4.png, Zygomaticotemporal suture
File:Sagittal suture.jpg, Sagittal suture.
File:Sagittal suture 2.jpg, Sagittal suture.
File:Sagittal suture 3.jpg, Sagittal suture.
File:Kort-lang-skalle.gif, Top view of cranial suture.
Syndesmosis
A syndesmosis is a slightly mobile fibrous joint in which bones such as the tibia and fibula are joined together by connective tissue. An example is the distal tibiofibular joint. Injuries to the ankle syndesmosis are commonly known as a "high ankle sprain". Although the syndesmosis is a joint, in the literature the term syndesmotic injury is used to describe injury of the syndesmotic ligaments. It comes from the Greek σύν, ''syn'' (meaning "with") and δεσμός, ''desmos'' (meaning "a band"). Syndesmosis sprains have received increasing recognition during recent years because of a heightened awareness of the mechanism, symptoms, and signs of injury.
Diagnosis of a syndesmotic injury
Diagnosis of syndesmosis injuries by physical examination is often straightforward. Physical examination findings that are often positive include the squeeze test and the external rotation test. Patients with high-grade syndesmosis injuries often cannot perform a single-leg heel raise. Patients report pain in varying degrees over the anterior and often posterior distal fibular joint.
Syndesmotic tear
The severity of acute syndesmosis injury is rated from grade I to III by several authors. A grade I injury is a partial anteroinferior tibiofibular ligament tear, meaning the exorotation and squeeze tests are negative for this grade. Grade II injury is a complete anteroinferior tibiofibular ligament and inferior interosseous ligament tear, meaning that squeeze test and exorotation are positive. This results in the injury being stabilized with immobilization but not operatively stabilized. A grade III injury is a complete anteroinferior tibiofibular ligament tear including a (partial) interosseous ligament tear and deltoid ligament avulsion, meaning the joint is unstable and positive on the exorotation and squeeze tests. This grade requires operative stabilization.
If the syndesmosis is torn apart as result of bone fracture, surgeons will sometimes fix the relevant bones together with a
syndesmotic screw, temporarily replacing the syndesmosis, or with a
tightrope fixation
Tightrope walking, also called funambulism, is the skill of walking along a thin wire or rope. It has a long tradition in various countries and is commonly associated with the circus. Other skills similar to tightrope walking include slack rope ...
, which is called
Syndesmosis Procedure. The screw inhibits normal movement of the bones and, thereby, the corresponding joint(s). When the natural articulation is healed, the screw may be removed. The tightrope fixation with elastic fiberwire suture on the other hand allows physiologic motion of the ankle and may be permanent.
Gomphosis
A gomphosis, also known as a
dentoalveolar syndesmosis,
is a joint that binds the
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, te ...
to bony
teeth sockets in the
maxillary bone and
mandible. The fibrous connection between a tooth and its socket is a
periodontal ligament
The periodontal ligament, commonly abbreviated as the PDL, is a group of specialized connective tissue fibers that essentially attach a tooth to the alveolar bone within which it sits. It inserts into root cementum one side and onto alveolar ...
. Specifically, the connection is made between the maxilla or mandible to the cementum of the tooth.
The motion of a gomphosis is minimal, though considerable movement can be achieved over time—the basis of using braces to realign teeth. The joint can be considered a
synarthrosis.
The gomphosis is the only joint-type in which a bone does not join another bone, as teeth are not technically bone. In modern, more anatomical, joint classification, the gomphosis is simply considered a fibrous joint because the tissue linking the structures is ligamentous. It has been suggested that this permanent soft-tissue attachment was a critical requisite in the evolution of the mammalian (
synapsid)
tusk.
A gomphosis is a specialized fibrous joint in which a conical process or peg of one bone fits into a hole or socket in another bone.
(gomphos is a Greek word meaning bolt). Small quantity of fibrous tissue holds the bones together.
No movement is possible at such peg-and-socket joints.
References
External links
*
Age at Death Estimation from Cranial Suture Closures
Cranial suture closure and its implications for age estimationfrom Douglas College
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Joints
Skull
it:Articolazione#Sindesmosi