Overview
This lecture covers the anatomy and movement of the elbow and wrist joints, their articulating bones, joint types, and the roles of different muscles during movement.
Elbow Joint Structure and Function
- The elbow joint is a uniplanar hinge joint allowing movement in one plane (flexion/extension).
- Three bones articulate at the elbow: humerus (upper arm), radius (thumb side forearm), and ulna (pinky side forearm).
- Flexion at the elbow is produced by the biceps brachii as the prime mover, with triceps brachii as the antagonist.
- Extension of the elbow is driven by the triceps brachii as the prime mover, with biceps brachii as the antagonist.
- The biceps brachii inserts on the radius; triceps brachii inserts on the ulna.
Muscle Actions and Examples
- During a football throw-in, the biceps cause elbow flexion; during the throw, the triceps cause elbow extension.
- In a push-up's downward phase, triceps brachii act as the prime mover during elbow flexion by lengthening (eccentric contraction) to control descent.
Wrist Joint Structure and Movements
- The wrist involves the radius, ulna, and multiple carpal (wrist) bones.
- The wrist joint is a condyloid (condylar) joint, not a hinge joint.
- The main wrist joint is the radiocarpal joint; the metacarpophalangeal joint in the fingers is also condyloid.
- Wrist flexion: wrist flexors (e.g., flexor digitorum superficialis, palmaris longus) are prime movers; wrist extensors are antagonists.
- Wrist extension: wrist extensors are prime movers; wrist flexors act as antagonists.
Key Terms & Definitions
- Hinge Joint — A joint that permits movement in one plane (e.g., elbow).
- Condyloid Joint — Joint allowing movement in two planes (e.g., wrist).
- Prime Mover (Agonist) — The muscle primarily responsible for movement.
- Antagonist — The muscle that relaxes to allow movement by the agonist.
- Flexion — Decreasing the angle between two bones (e.g., bending the elbow).
- Extension — Increasing the angle between two bones (e.g., straightening the elbow).
- Isotonic Eccentric Contraction — Muscle lengthens under tension, controlling movement.
Action Items / Next Steps
- Study muscle insertions (biceps on radius, triceps on ulna) for upcoming work on levers.
- Review types of muscle contractions, especially isotonic eccentric contractions.
- Learn specific names and actions of the wrist flexor and extensor muscles.