Immovable Joint

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Immovable joint

Definition

An immovable joint is an articulation between bones in which no movement occurs. It is also referred to as synarthrotic (meaning immovable).

Description

An immovable joint can be either one of two types of joints, fibrous or cartilaginous. In a fibrous joint, there are two types of articulations that are considered immovable, suture and gomphosis.

A suture is a type of articulation in which the bones that make up the joint are close together. An analogy to this is the interlocking fashion exhibited by placing puzzle pieces together. In a suture, the union of bones is bound by connective tissue.

A gomphosis is a type of joint in which one bone fits into another bone. The articulating edges are bound together by connective tissue. Similar to the suture, the bony surfaces in the articulation are close together. An analogy to this is a wooden dowel fitting into a hole and held together by glue, with the dowel and hole representing the bony structures and the glue representing the connective tissue.

In a cartilaginous type of joint, there is one type of articulation that is considered immovable, the synchondrosis.

A synchondrosis is a joint in which the articulating surfaces are close together but are bound by hyaline cartilage. In a synchondrosis, the hyaline cartilage eventually converts to either bone or fibrocartilage.

Function

The function of the immovable or synarthrotic joint is to provide a stable union between bony surfaces. The suture and synchondrosis actually become more stable when ossification of the joint takes place.

KEY TERMS

Cartilaginous joint —A joint that represents the connection of two bones bound by either hyaline fibro or elastic cartilage.

Connective tissue —Tissue that has pliable fibers, which provide strength to the tissue.

Diaphysis —The center or shaft of a bone that is ossified.

Epiphysis —Considered a secondary center of ossification. This secondary center of ossification appears at the ends of long bone.

Fibrocartilage —Connective tissue made up of collagen fibers with less ground substance compared to hyaline cartilage.

Fibrous joint —Surfaces of two bones that are connected by fibrous tissue, which consists mainly of collagen fibers.

Hyaline cartilage —A mesh of collagen fibers and ground substance.

Proximal —The closest portion of a bone, structure, or other element that is close to the head of the body.

Synarthrosis —An immovable joint.

Role in human health

An example of a suture in the human body is the fibrous joints between the bones of the skull . Before birth the suture is fibrous tissue that forms soft spots on the skull. The common medical term is fontanelle. The fibrous joint between the bones of the skull allows the skull to be more pliable during birth as the head passes through the vagina. During infancy the pliable nature of the skull, secondary to fibrous sutures, allows for growth of the brain . As growth and development occurs the sutures become ossified.

An example of a gomphosis in the human body is the joining of the root of a tooth with the mandible or jaw bone. The fibrous union between the tooth and the bone secures the tooth in its position. This allows the teeth to function as grinders during chewing.

An example of synchondrosis in the human body is two distinct portions of long bone that are separated by a hyaline cartilaginous plate. This typically occurs at the ends of long bones where a cartilaginous plate separates the diaphysis from the epiphysis. This plate allows the end of bones to grow throughout early human development. As growth and development continue, the hyaline cartilage ossifies. By adulthood the joint is gone. Another example of a synchondrosis in the human body is the articulation between the first rib and the manubrium or the upper portion of the sternum. Initially, the connection between the manubrium and first rib is hyaline cartilage. Through adulthood the hyaline cartilage is replaced by fibrocartilage. This process allows the superior portion of the thorax to be more secure and stable.

Common diseases and disorders

The most common disorder of sutures or fontanelles of the skull is the disruption of the bony components, thus compromising the integrity of the fibrous attachment. This could occur as a result of head injury from a blow to the head or a fall. Common disorders of the teeth that compromise the integrity of the fibrous attachment of tooth to bone are: fracture of the jaw bone, fracture of the tooth, avulsion of the tooth, loosening of the tooth secondary to decay, or a blow to the head or jaw. The most common disorder associated with a synchondrosis is a disruption of the epiphyseal hyaline cartilage plate. This is particularly evident in the proximal femur, specifically related to the hip. This disorder occurs mainly in young children as a result of a fall or other trauma. This disruption to the plate can lead to fracture, disruption of blood supply, and, if not treated appropriately, deformity of the hip. The medical term for this disorder is slipped capital femoral epiphysis.