Page 52 - Alaska A & P Primer

9.1 Classification of Joints
9.2 Fibrous Joints
9.1 OBJECTIVES
1. Distinguish between the functional and structural classifications for joints, and an example of three functional types of
9.2 OBJECTIVES
1. Distinguish between a suture, syndesmosis, and gomphosis
Structural classifications of the body joints are based on how the bones are held together and articulate with each other. At fibrous joints, the adjacent bones are directly united to each other by fibrous connective tissue. Similarly, at a cartilaginous joint, the adjacent bones are united by cartilage. In contrast, at a synovial joint, the articulating bone surfaces are not directly united to each other, but come together within a fluid-filled joint cavity.
The functional classification of joints is determined by the amount of mobility found be- tween the adjacent bones. Joints are thus functionally classified as a synarthrosis or immo- bile joint, an amphiarthrosis or slightly moveable joint, or as a diarthrosis, which is a
freely moveable joint (arthroun = “to fasten by a joint”). Depending on their location, fi- brous joints may be functionally classified as a synarthrosis (immobile joint) or an amphi- arthrosis (slightly mobile joint). Cartilaginous joints are also functionally classified as ei- ther a synarthrosis or an amphiarthrosis joint. All synovial joints are functionally classified as a diarthrosis joint.
The most common type of joint is the diarthrosis, which is a freely moveable joint. All syno- vial joints are functionally classified as diarthroses. A uniaxial diarthrosis, such as the el- bow, is a joint that only allows for movement within a single anatomical plane. Joints that allow for movements in two planes are biaxial joints, such as the metacarpophalangeal joints of the fingers. A multiaxial joint, such as the shoulder or hip joint, allows for three planes of motions.
Fibrous joints form strong connections between bones. (a) Sutures join most bones of the skull. (b) An interosseous membrane forms a syndesmosis between the radius and ulna bones of the forearm. (c) A gomphosis is a specialized fibrous joint that anchors a tooth to its socket in the jaw.
9.3 Cartilaginous Joints
As the name indicates, at a cartilaginous joint, the adjacent bones are united by cartilage, a tough but flexible type of connective tissue. These types of joints lack a joint cavity and in- volve bones that are joined together by either hyaline cartilage or fibrocartilage . There are two types of cartilaginous joints. A synchondrosis is a cartilaginous joint where the bones are joined by hyaline cartilage. Also classified as a synchondrosis are places where bone is united to a cartilage structure, such as between the anterior end of a rib and the costal car- tilage of the thoracic cage. The second type of cartilaginous joint is a symphysis, where the bones are joined by fibrocartilage
9.3 OBJECTIVES
1. Describe the structural features of cartilaginous joints
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State of Alaska EMS Education Primer - 2016
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