UNIT 4.4 JOINTS 23 24 Foundation PDF

OUTLINE 4.4 Joints. 4.4.1 Joint classification. Structural classification Functional classification: based on movement 4.4.2 Fibrous joints 4.4.3 Cartilaginous joints 4.4.4 Synovial joints Structure of the synovial joints Movement of synovial joints Types of synovial joints © Copyright Universidad...

OUTLINE 4.4 Joints. 4.4.1 Joint classification. Structural classification Functional classification: based on movement 4.4.2 Fibrous joints 4.4.3 Cartilaginous joints 4.4.4 Synovial joints Structure of the synovial joints Movement of synovial joints Types of synovial joints © Copyright Universidad Europea. Todos los derechos reservados STRUCTURE of SYNOVIAL JOINTS Synovial cavity separates articulating bones. Freely movable (diarthroses). Articular cartilage (covers the articulating surfaces): § reduces friction; § absorbs shock. Articular capsule: surrounds joint (movement/anti-dislocation/nutrition/defense): § Fibrous capsule (dense irregular connective): • thickenings in fibrous capsule: ligaments. § Synovial membrane: • inner lining of capsule (areolar connective tissue, macrophages and synoviocytes). © Copyright Universidad Europea. Todos los derechos reservados Examples of synovial joints Ribs to sternum except 1st rib © Copyright Universidad Europea. Todos los derechos reservados ARTICULAR CAPSULE Surrounds a diarthrosis, encloses synovial cavity and unites the articular bones. It has two layers - the outer fibrous capsule (which may contain ligaments made of bundles of fibers) and the inner synovial membrane (which secretes a lubricating and jointnourishing synovial fluid and contains elastic fibers). Synovial fluid: hyaluronic acid secreted by synoviocytes and interstitial fluid from plasma. It reduces friction and helps nourish the avascular articular cartilage. It brings nutrients and oxygen to the chondrocytes of the articular cartilage. The flexibility of the fibrous capsule permits considerable movement at joints, whereas its great tensile strength (= resistance to stretching) helps prevent bones from dislocating. Other capsule features include ligaments and articular fat pads. © Copyright Universidad Europea. Todos los derechos reservados SYNOVIAL MEMBRANE Lines the synovial cavity (except the articular cartilage) – Synoviocytes secrete synovial fluid which contains slippery hyaluronic acid and interstitial fluid from plasma. • It reduces friction and helps nourish the avascular articular cartilage. • It brings nutrients and oxygen to the chondrocytes of the articular cartilage. Internal use OTHER ELEMENTS OF SYNOVIAL JOINTS • Meniscus or articular disc: It is a cushion of fibrocartilage placed between the articular ends of some diarthrosis. It allows two bones of different shape to fit tightly. It divides the articular cavity in 2 independent compartments. It increases the stability of the joint. Accessory ligaments: § Strong cords or lamina of fibrous tissue in most synovial joints. Important for capsule reinforcement. Labrum = fibrocartilaginous lip that extends from edge of joint socket increasing contact area § In shoulder and hip. © Copyright Universidad Europea. Todos los derechos reservados SPECIAL FEATURES around SYNOVIAL JOINTS BURSAE – Are not a part of synovial joints. – Sac-like structures. Located between skin and bones, tendons and bones, muscles and bones, and ligaments and bones. – Alleviate friction. – Outer fibrous membrane of dense connective tissue lined by synovial membrane. – Filled with fluid (similar to synovial fluid) – BURSITIS = inflammation of synovial membrane and excess production of synovial fluid. Upper limb Internal use SPECIAL FEATURES around SYNOVIAL JOINTS TENDON SHEATHS – Reduce tension at joints. – Tube-like bursae that wrap around certain tendons subjected to friction. – 2 layers: • Inner (visceral) layer attached to tendon. • Outer (parietal) layer attached to bone. – There is synovial fluid between layers. – Found in tendons that go through synovial cavities; in shoulder, fingers, toes, wrist and ankle. Internal use NERVE AND BLOOD SUPPLY INNERVATION: Nerves to joints are branches of nerves to nearby muscles. Articular capsule and ligaments contain pain and other sensory receptors. VASCULARIZATION: Blood supply of a joint consists of branches from nearby structures and supply nutrients to all joint tissues except the articular cartilage (which is covered with synovial fluid). © Copyright Universidad Europea. Todos los derechos reservados