Joints and Articulation

Unit 2: Joints Study Guide Joints and Articulation Classification of Joints Define a joint: ● ● ● ● Articulation - site where two or more bones meet The rigid elements of the skeleton meet at sites called joints Weakest parts of the skeleton Functions of a joint: ○ Give the skeleton mobility ○ Hold the skeleton together, support. Compare the structural and the functional classification of joints: ● ● Structural classification focuses on the material binding bones together and whether a joint cavity is present. ○ There are three structural classifications of joints: ■ Fibrous – bones united by collagenic fibers ● Sutures (short fibers) – immobile (synarthrosis) ● Syndesmosis (longer fibers) – slightly mobile (amphiarthrosis) and immobile ● Gomphosis (periodontal ligament) - immobile ■ Cartilaginous – bones ends/parts united by cartilage ● Synchondrosis (hyaline cartilage) – immobile ● Symphysis (fibrocartilage) – slightly movable ■ Synovial – bone ends/parts covered with articular cartilage and enclosed within an articular capsule lined with synovial fluid ● Plane, hinge, pivot, condylar, saddle, ball and socket – freely movable Functional classification focuses on the amount of movement allowed. ○ There are three functional classifications of joints: ■ Synarthroses - immovable joints ■ Amphiarthroses - slightly movable joints ■ Diarthroses - freely movable joints Know the three types of cartilage, where they can be found and characteristics and functions of each: ● ● ● Hyaline ○ Provides support, flexibility and resilience ○ It’s the most abundant skeletal cartilage ○ The only type of fiber found in the hyaline cartilage matrix is a collage unit fibril, which forms networks that are too thin to be seen with a light microscope. ○ Found in: ■ Articular - covers the end of long bones ■ Costal - connects ribs to the sternum ■ Respiratory - makes up the larynx and reinforces air passages ■ Nasal - supports the structure of the nose Elastic ○ Similar to hyaline cartilage except its matrix contains many elastic fibers along with the delicate collagen fibrils. It’s more flexible and tolerates repeated bending ○ Found in the epiglottis and the external ear Fibrocartilage ○ An usual tissue that resists both strong compression and strong tensions ○ It consists of two rows of thick collagen fibers alternating with rows of chondrocytes ○ Found in intervertebral discs and menisci of the knee Fibrous Joints ● ● ● ● Bones joined by fibrous tissues, namely dense regular connective tissue. No joint cavity present Most are immovable There are 3 types: ○ Gomphoses (synarthrosis) ○ Sutures (synarthrosis) ○ Syndesmoses (amphiarthrosis) Gomphoses (periodontal ligament) Explain the location and characteristics of gomphoses: ● ● The peg-in-socket joint The only example is the articulation of a tooth with its socket. In this case, the connecting ligament is the short periodontal ligament. Sutures (short fibers) Describe the location and functions of sutures: ● ● ● ● ● Only occur between the bones of the skull and their fibrous tissue is continuous with the periosteum around these flat bones Bones are tightly bound by a minimal amount of fibrous tissue The edges of the joining bones are wavy and interlocking Sutures not only knit the bones together but also allow growth in youth so that the skull can expand with the brain during childhood. During middle age, the fibrous tissue ossifies and the skull bones fuse together. At this stage, the close sutures are more precisely called synostoses, literally meaning “bony junction”. The immovable nature of sutures is a protective adaptation. Syndesmoses (longer fibers) Name the locations of syndesmoses and describe their function: ● ● ● Bones are connected exclusively by ligaments, bands of fibrous tissue longer than those that occur in the suture. The name syndesmosis derives from the Greek word for “ligament.” Movement varies from immovable to slightly movable. The amount of movement allowed at a syndesmosis depends on the length of the connecting fibers. If the fibers are short, as in the distal tibiofibular articulation, little to no movement is allowed and the joint is synarthrotic. If the fibers are quite long, as in the interosseous membrane between the radius and ulna, a large amount of movement is possible and the joint is diarthrotic. Found in connections like the tibia and fibula, and the radius and the ulna