Joints P A R T A

Joints (Articulations) Weakest parts of the skeleton Articulation – site where two or more bones meet Functions of joints Give the skeleton mobility Hold the skeleton together

Classification of Joints: Structural Structural classification focuses on the material binding bones together and whether or not a joint cavity is present The three structural classifications are: 1. Fibrous 2. Cartilaginous 3. Synovial

Classification of Joints: Functional Functional classification is based on the amount of movement The three functional classes of joints are: 1. Synarthroses – immovable 2. Amphiarthroses – slightly movable 3. Diarthroses – freely movable

Fibrous Structural Joints The bones are joined by fibrous tissues No joint cavity Most are immovable There are three types – sutures, syndesmoses, and gomphoses

Fibrous Structural Joints: Sutures Occur between the bones of the skull Comprised of interlocking junctions filled with connective tissue fibers Bind bones tightly together, but allow for growth during youth Fusion of bones = synostoses

Fibrous Structural Joints: Sutures Figure 8.1a

Fibrous Structural Joints: Syndesmoses Bones are connected by a fibrous ligament Either immovable or slightly moveable Examples include the connections between the tibia and fibula, and the radius and ulna

Fibrous Structural Joints: Syndesmoses Figure 8.1b

Fibrous Structural Joints: Gomphoses The peg-in-socket fibrous joint between a tooth and its alveolar socket The fibrous connection is the periodontal ligament

Cartilaginous Joints Articulating bones are united by cartilage Lack a joint cavity Two types – synchondroses and symphyses

Cartilaginous Joints: Synchondroses A plate of hyaline cartilage unites the bones All synchondroses are synarthrotic Examples include: Epiphyseal plates of children Joint between the first rib and the sternum

Cartilaginous Joints: Synchondroses Figure 8.2a, b

Cartilaginous Joints: Symphyses Hyaline cartilage covers bone and is fused to a pad of fibrocartilage Amphiarthrotic joints designed for strength and flexibility Examples include intervertebral joints and the pubic symphysis of the pelvis

Cartilaginous Joints: Symphyses Figure 8.2c

Synovial Joints Bones are separated by a fluid-containing joint cavity All are freely movable diarthroses Examples – all limb joints, and most joints of the body

Synovial Joints: General Structure Synovial joints all have the following Articular cartilage Joint (synovial) cavity Articular capsule Synovial fluid Reinforcing ligaments

Synovial Joints: General Structure Figure 8.3a, b

Synovial Joints: Friction-Reducing Structures Bursae – flattened, fibrous sacs containing synovial fluid Common where ligaments, muscles, tendons, or bones rub together Tendon sheath – elongated bursa that wraps completely around a tendon

Synovial Joints: Friction-Reducing Structures Figure 8.4

Synovial Joints: Stability Stability is determined by: 1. Articular surfaces – shape determines what movements are possible 2. Ligaments – prevent excessive or undesirable motion

Synovial Joints: Movement The two muscle attachments across a joint are: 1. Origin – attachment to the immovable bone 2. Insertion – attachment to the movable bone Described as movement along transverse, frontal, or sagittal planes

Synovial Joints: Range of Motion Nonaxial – slipping movements only Uniaxial – movement in one plane Biaxial – movement in two planes Multiaxial – movement in or around all three planes

Gliding Movements Nonaxial One flat bone surface glides or slips over another Examples – intercarpal and intertarsal joints, and between the vertebrae

Angular Movement Flexion — decreases the angle of the joint Extension — reverse of flexion; joint angle is increased Dorsiflexion and plantar flexion — up and down movement of the foot

Angular Movement Abduction — movement away from the midline Adduction — movement toward the midline Circumduction — movement describes a cone in space

Gliding Movement Figure 8.5a

Angular Movement Figure 8.5b

Angular Movement Figure 8.5c, d

Angular Movement Figure 8.5e, f

Rotation The turning of a bone around its own long axis Uniaxial Examples Between first two vertebrae Hip and shoulder joints Figure 8.5g

Special Movements Supination and pronation Inversion and eversion Protraction and retraction Elevation and depression Opposition

Special Movements Figure 8.6a

Special Movements Figure 8.6b

Special Movements Figure 8.6c

Special Movements Figure 8.6d

Special Movements Figure 8.6e