Skeletal systems: Joints

Key Words and Topics Make certain that you can define, and use in context, each of the terms listed below, and that you understand the significance of each of the concepts. 1. Define the term “articulation” (joint). • articulation or arthrosis A joint, also called an articulation or arthrosis is a point of contact between two bones, between bone and cartilage, or between bone and teeth. When we say one bone articulates with another bone, we mean that the bones form a joint. 2. Classify joints on the basis of structure and function. • structural classification -The structural classification of joints is based on two criteria: (1) the presence or absence of a space between the articulating bones, called a synovial cavity, and (2) the type of connective tissue that binds the bones together. Structurally, joints are classified as one of the following types: • fibrous joints- There is no synovial cavity, and the bones are held together by dense irregular connective tissue that is rich in collagen fibers. • cartilaginous joints- There is no synovial cavity, and the bones are held together by cartilage. • synovial joints- The bones forming the joint have a synovial cavity and are united by the dense irregular connective tissue of an articular capsule, and often by accessory ligaments. • functional classification • synarthrosis- An immovable joint. The plural is synarthroses. • Amphiarthrosis-A slightly movable joint. The plural is amphiarthroses. • Diarthrosis- A freely movable joint. The plural is diarthroses. All diarthroses are synovial joints. They have a variety of shapes and permit several different types of movements. 3. Describe the structure and functions of the three types of fibrous joints. • fibrous joints (see above for definition) • suture A suture (SOO‐chur; sutur = seam) is a fibrous joint composed of a thin layer of dense irregular connective tissue; sutures occur only between bones of the skull. An example is the coronal suture between the parietal and frontal bones (Figure 9.1a). The irregular, interlocking edges of sutures give them added strength and decrease their chance of fracturing. Sutures are joints that form as the numerous bones of the skull come in contact during development. They are immovable or slightly movable. In older individuals, sutures are immovable (synarthroses), but in infants and children they are slightly movable (amphiarthroses) (Figure 9.1b). Sutures play important roles in shock absorption in the skull.