Articulations Chapter 6

Classification of Joints (Articulations): Joint- Where two bones interact Three functional classes of joints Synarthroses Immovable – e.g., sutures Amphiarthroses Slightly movable – e.g., pubic symphysis, distal radius/ulna Diarthroses Freely movable – e.g., shoulder, elbow etc.

Classification of Joints (Articulations): Three structural classes of joints Fibrous No space between articulating bones; held together by dense connective tissue – e.g., sutures, distal radius/ulna May be functionally synarthroses or amphiarthroses Cartilagenous No space between articulating bones; held together by cartilage – e.g., pubic symphysis May be funtionally synarthroses or amphiarthroses Synovial Space (synovial/joint cavity) between articulating bones – e.g., shoulder, elbow etc. Functionally are diarthroses

The Structure of Synovial Joints

The Structure of Synovial Joints

Movements ocurring at synovial joints Flexion Extension Hyperextension

Lateral flexion Abduction Adduction Rt. lateral flexion Lt. lateral flexion

Rotation: Left/Right Medial (internal) Lateral (external)

Pronation Supination

Dorsiflexion/Plantarflexion Inversion/Eversion Elevation/Depression Protraction/Retraction Opposition

Movement at synovial joints occurs through contraction of skeletal muscles When skeletal muscles contract, they pull on bones of the skeleton at their attachment points, creating movement in a particular direction (or directions)

Origin - Muscle attachment that remains fixed Insertion - Muscle attachment that moves Action - What movement a muscle produces. Movement usually occurs at joints i.e. flexion, extension, abduction, etc.

For muscles to create a movement, they can only pull, not push Muscles in the body rarely work alone, & are usually arranged in groups surrounding a joint A muscle that contracts to create the desired action is known as an agonist or prime mover A muscle that helps the agonist is a synergist A muscle that opposes the action of the agonist, therefore undoing the desired action is an antagonist

Skeletal muscle movements Flexion/extension Abduction/adduction Rotation – left/right; internal(medial)/external(lateral) Pronation/supination Elevation/depression Protraction/retraction Dorsiflexion/plantarflexion Inversion/eversion *note: muscles of facial expression (e.g. orbicularis oculi; orbicularis oris) produce movements of the features of the face, and therefore the actions use more descriptive terminology