Joints Lecture 5 PDF

Joints Joints  Joints are articulations – the place of union or junction between two or more bones or parts of bones  Joints have different form and function – from no to slight to freely movable Classification  Three types of joints  Synovial  Fibrous  Cart...

Joints Joints  Joints are articulations – the place of union or junction between two or more bones or parts of bones  Joints have different form and function – from no to slight to freely movable Classification  Three types of joints  Synovial  Fibrous  Cartilaginous  Classified according to the manner or type of material by which articulating bones are united Synovial Joints  An articular capsule spans and encloses the articulating surfaces and joint cavity. Composed of a fibrous capsule lined with synovial membrane.  Articular cartilage covers the articular surfaces of bones  The joint cavity enclosed by the capsule contains synovial fluid. The joint cavity is a potential space that contains a small amount of synovial fluid.  All internal structures in a synovial joint that are not covered with articular cartilage are covered with a synovial membrane. Synovial Joints Synovial Joints  Synovial joints are the most common types of joints  They allow free movement between the bones they join – are typical of nearly all limb joints.  Synovial fluid in the joint (synovial) cavity acts as a lubricant  The synovial membrane is a vascular connective tissue that produces the synovial fluid  Can be reinforced by accessory ligaments. Synovial Joints Classified according to the shape of the articulating surface and/or the type of movement they permit Synovial Joints  Hinge Joints  Allow movement in one plane around only one axis  Allow flexion and extension only  E.g. Elbow joint  Their capsule is thin and lax anteriorly and posteriorly where movement occurs, however they have strong lateral collateral ligaments  Plane Joints (Gliding)  Numerous and small  Allow gliding or sliding movement  Uniaxial  E.g. Acromioclavicular joint Synovial Joints  Condyloid Joints  Biaxial , the two axes lie perpendicular to each other  Movement in one axis is freer  E.g. Metacarpopharyngeal joints (knuckles)  Saddle Joints  Biaxial, opposing surfaces shaped like a saddle (Concave-convex at the articulating surfaces)  1st Carpometacarpal Joint – base of thumb Synovial Joints  Ball and socket joints -  Multiaxial – move in multiple axes and planes  Spheroidal surface of one bone moves within socket of another  E.g. Head of femur in acetabulum of pelvis  Allow flexion, extension, abduction, adduction, medial and lateral rotation  Pivot joints  Uniaxial and allow rotation  A rounded process of a bone rotates within a sleeve or ring  E.g. Rotation of radius in pronation/supination of forearm and the atlantoaxial joint - C1 around the odontoid process of C2 in rotation of head Fibrous Joints  United by fibrous tissue  The range of movement allowed by fibrous joints depends on the length of fibres uniting the bones  E.g sutures of the skull – bones are close together  A syndesmosis is a type of fibrous joint that unites the bones with a sheath of fibrous tissue e.g. Interosseous membrane of forearm Fibrous Joints Fibrous Joints  A gomphosis (dentoalveolar syndesmosis) is a type of fibrous joint where a peg-like process fits into a socket articulation between the root of the tooth and alveolar process (socket) Cartilaginous Joints  United by hyaline cartilage or fibrocartilage  Primary Cartilaginous joints – synchondroses  Bones are united by hyaline cartilage  Temporary – as in the development of long bone where the epiphysis and diaphysis are joined by an epiphyseal plate  Allows linear growth in bone  When full growth is achieved, the epiphyseal plate converts to bone and the epiphysis is fused to the diaphysis. Cartilaginous Joints Secondary cartilaginous joints (Symphyses) are strong, slightly movable and united by fibrocartilage E.g. the fibrocartilaginous intervertebral discs that join the vertebrae together, providing strength and shock absorption and considerable flexibility to the spine. Vasculature  Joints receive blood supply from articular arteries that arise from blood vessels around the joint  These often join to form arterial articular networks – anastomoses  This ensures a blood supply to and across the joint in the various positions assumed by the joint Vasculature Innervation  Joints have a rich nerve supply, with nerve endings in the articular capsule  In the hands and feet, the articular nerves are branches of the cutaneous nerves that supply the overlying skin  Most articular nerves are branches of nerves that supply the muscles that cross and therefore move the joint  Joint transmit proprioception – joint position sense. This provides awareness of position and movement of body parts.