Overview
This lecture covers the key muscles that move the elbow joint and forearm, focusing on their origins, insertions, actions, and notable landmarks.
Muscles of Elbow Flexion
- Elbow flexors include biceps brachii, brachialis, and brachioradialis; they are synergists.
- Biceps brachii has two heads: long head (origin: glenoid cavity, lateral) and short head (origin: coracoid process, medial).
- Both biceps heads insert on the radial tuberosity to flex the elbow.
- Brachialis originates on the humerus and inserts on the ulnar tuberosity.
- Brachioradialis originates from the humerus and inserts on the radius.
Muscles of Elbow Extension
- Triceps brachii has three heads: lateral, long, and medial.
- All triceps heads insert on the olecranon process of the ulna to extend the elbow.
- Lateral and medial heads originate on the humerus; long head originates on the scapula.
- Anconeus is a small muscle at the elbow assisting extension.
Muscles of Forearm Flexion and Pronation
- Most anterior forearm muscles are flexors or pronators.
- Pronator teres originates on the medial epicondyle and inserts on the radius for forearm pronation.
- Palmaris longus (may be absent in some people) originates at the medial epicondyle, inserts on the palmar aponeurosis, and aids wrist flexion.
Wrist Flexors and Related Muscles
- Flexor carpi radialis and flexor carpi ulnaris both originate at the medial epicondyle and insert on metacarpals to flex the wrist.
- Flexor carpi radialis is on the radial (thumb) side; flexor carpi ulnaris is on the ulnar (pinky) side.
- These muscles also help with wrist abduction (radialis) and adduction (ulnaris).
Finger Flexors
- Flexor digitorum superficialis (superficial) and flexor digitorum profundus (deep) flex the fingers, inserting on the phalanges.
- Flexor pollicis longus flexes the thumb, inserting on the thumb's phalanges.
Muscles of Forearm and Finger Extension
- Posterior forearm muscles originate on the lateral epicondyle and act as extensors.
- Extensor carpi radialis (longus and brevis) and extensor carpi ulnaris extend the wrist; radialis abducts and ulnaris adducts the wrist.
- Extensor digitorum extends the fingers by inserting on the phalanges.
- Extensor digiti minimi extends the pinky finger.
- Extensor pollicis longus and brevis extend the thumb.
- Abductor pollicis longus abducts the thumb.
Key Terms & Definitions
- Origin — where a muscle begins, usually on a stable bone.
- Insertion — where a muscle attaches to moveable bone.
- Synergist — muscles that work together to produce the same action.
- Flexion — decreasing the angle between bones (bending).
- Extension — increasing the angle between bones (straightening).
- Abduction — movement away from the midline.
- Adduction — movement toward the midline.
- Pronator — a muscle that turns the palm downward.
- Palmar aponeurosis — sheet-like tendon in the palm.
Action Items / Next Steps
- Use 3D models or videos to visualize muscle layers and their locations.
- Practice identifying muscle origins and insertions on diagrams and your own arm.
- Watch the supplemental video for locating palmaris longus.