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Anatomy Study Guide Joints Joints(articulations) – elements that are rigid in the skeleton meet at joints. Classify joints by structure and by function Functional classification focuses on the amount of movement allowed Synarthroses – immovable joints   Amphiarthroses – slightly movable joints  Diarthroses – freely movable joints Structural classification is based on the material that binds the bones together and on the presence or absence of a joint cavity  Fibrous bones are connected by fibrous tissue; dense regular connective tissue, no joint cavity is present, immovable or only slightly movable  Sutures – joints held together w/very short interconnecting fibers, and bone edges interlock found only in the skull  Syndesmosis – joint is held together by a ligament. Fibrous tissues can vary in length but is longer than in sutures  Gomphosis – peg-in-socket fibrous joint, periodontal ligament holds tooth in socket  Cartilaginous – articulating bones are united by cartilage; joints lack a joint cavity and are not highly movable  Synchondrosis(hyaline cartilage) – junction of cartilage, immovable synarthroses  Symphysis(fibrocartilage) – growing together, slightly movable joints; fibrocartilage resists both tension and compression and can act as a resilient shock absorber  Synovial Joints – most movable joints of the body, all diarthroses, synovial joint contains a fluid filled joint cavity  Articular cartilage – the ends of the opposing bones are covered by articular cartilages composed of hyaline cartilage  Joint cavity – a potential space that holds a small amount of synovial fluid  Articular capsule – joint cavity is enclosed by a 2 layered articular capsule o Fibrous layer dense irregular connective tissue is continuous w/ the periosteum layer of the joining bones o Synovial membrane – composed of loose connective tissue; fx is to make synovial fluid  Synovial fluid – liquid inside the joint cavity; resembles raw egg white; primarily a filtrate of blood arising from capillaries in the synovial membrane o Weeping lubrication – nourishes he cells in the articular cartilages and lubricates the free surfaces of these cartilages, allowing the adjoining bones to move across each other w/ a minimum of friction  Reinforcing ligaments – the ligaments are capsular, they are thickened parts of the fibrous layer of the articular capsule o Extracapsular ligaments are located just outside the capsule, for instance, the fibular and tibial collateral o the knee\ o Intracapsular ligaments are internal to the capsule for ex. the anterior and posterior cruciate ligaments in the knee  Nerves & Vessels – synovial joints are richly supplied w/ sensory nerve fibers that innervate the articular capsule, most of the blood vessels supply the synovial

Anatomy Study Guide Joints membrane, where extensive capillary beds produce the blood filtrate that is the basis of synovial fluid  Articular disc(meniscus) – certain synovial joints contain a disc of fibrocartilage, fills the gaps and improves the fit, thereby disturbing the load more evenly and minimizing wear and damage  Bursae & Tendon sheaths – contain synovial fluid, not synovial joints, closed bags of lubricants o Bursa – a flattened fibrous sac lined by a synovial membrane o Tendon sheath – essentially an elongated bursa that wraps around a tendon like a hot dog bun Movements Allowed by Synovial Joints  Gliding – sliding the flat surfaces of 2 bones across each other  Angular movements  Flexion, Extension, Abduction, Adduction, Circumduction  Rotation – turning a bone around the longitudinal axis Stability of Synovial Joints  Articular surfaces – a joint fit together in a complementary manner  Ligaments – help hold the bones together and prevent excessive or undesirable motions  Muscle Tone – a constant low level of contractile force generated by a muscle even when it is not causing movement; helps stabilize joints by keeping tension on the muscle tendons that cross over joints just external to the joint capsule Types of Synovial Joints  Nonaxial – adjoining bones do not move around a specific axis Ex. Plane  Uniaxial – movement occurs around a single axis Ex. Hinge, Pivot  Biaxial – movement can occur around 2 axes, thus, the joint enables motion along both the frontal & sagittal planes Ex. Condylar, Saddle  Multiaxial – movement can occur around all 3 axes and along all 3 body planes: frontal, sagittal, & transverse Ex. Ball&Socket Selected Synovial Joints Temporomandibular Joint – jaw joint; modified hinge joint; lies anterior to the ear Sternoclavicular Joint – a saddle joint; Glenohumeral (shoulder) Joint – stability has been sacrificed to provide the most freely moving joint of the body Hip Joint – ball and socket; wide range of motion but not as much as the shoulder Knee Joint – the largest and most complex joint in the body primarily acts as a hinge(P230)

D/O of Joints  Torn Cartilage – cartilage tears in the knee often happen when a meniscus is simultaneously subjected to both high compression and shear stresses Sprains - the ligaments reinforcing a joint are stretched or torn   Dislocation – occurs when the bones of a joint are forced out of alignment Inflammatory & Degenerative Conditions

Anatomy Study Guide Joints      

Bursitis – inflammation of a bursa, usually results from a physical blow or friction, although it may also be caused by arthritis or bacterial infection Tendonitis – inflammation of a tendon Arthritis – describe over 100 kinds of inflammatory or degenerative disease that damage the joints Osteoarthritis – a chronic degenerative condition that is often called wear and tear arthritis Rheumatoid Arthritis – a chronic inflammatory d/o. Gouty Arthritis –rate of excretion is low, uric acid levels rise abnormally in blood and body fluids and the acid precipitates as solid crystals of urate in the synovial membranes...