Articulations Chapter 6 n Classification of Joints Articulations

Articulations Chapter 6

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

n Classification of Joints (Articulations): ¨ Three structural classes of joints n Fibrous No space between articulating bones; held together by dense connective tissue – e. g. , sutures, distal radius/ulna ¨ May be functionally synarthroses or amphiarthroses ¨ n Cartilagenous No space between articulating bones; held together by cartilage – e. g. , pubic symphysis ¨ May be funtionally synarthroses or amphiarthroses ¨ n 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