Overview
This lecture provides strategies and mnemonics to help remember the skeletal muscles of the upper limb, organized into logical muscle groups for easier study.
Back Muscles
- Trapezius originates from the skull and thoracic vertebrae, inserts on scapula and clavicle, and moves the shoulder in multiple ways.
- Latissimus dorsi (lats) is the widest muscle, spanning back and inserting on the humerus, important for arm movement.
- Rhomboid major and minor retract the scapula; major is rhomboid-shaped and minor is above it, more cylindrical.
- Levator scapulae elevates the scapula, attaching from high cervical vertebrae to upper scapula.
Chest Muscles
- Pectoralis major (large, superficial) and pectoralis minor (smaller, deep) move the arm and shoulder.
- Serratus anterior has a jagged edge, aids in protracting the scapula.
- Intercostal muscles are located between the ribs, aiding respiration.
Shoulder Muscles
- Deltoid is triangular, covering the shoulder, main abductor of the arm.
- Rotator cuff muscles (SITS): Supraspinatus (above scapular spine), Infraspinatus (below spine), Teres minor (small, angled), Subscapularis (under scapula).
- Teres major is a larger, powerful mover of the arm, not part of the rotator cuff.
Upper Arm Muscles
- Biceps brachii (two-headed) flexes the elbow; triceps brachii (three-headed) extends it.
- Coracobrachialis attaches from coracoid process to humerus, aids in flexion and adduction.
- Brachialis is a deep elbow flexor.
- Brachioradialis connects upper arm to radius, aids in forearm flexion.
- Anconeus is a small accessory elbow extensor.
Forearm Muscles (Anterior)
- Flexor carpi radialis and ulnaris flex the wrist on respective sides.
- Palmaris longus has a long tendon, often absent in some people.
- Pronator teres/pronator quadratus pronate the forearm.
- Flexor digitorum superficialis/profundus flex fingers at different depths.
- Flexor pollicis longus flexes the thumb.
Forearm Muscles (Posterior)
- Extensor carpi ulnaris/radialis (longus and brevis) extend the wrist on respective sides.
- Extensor digitorum extends the fingers; extensor digiti minimi extends the pinky.
- Extensor indicis extends the index finger.
- Abductor pollicis longus and extensor pollicis longus/brevis move and extend the thumb.
- Supinator muscle supinates the forearm near the elbow.
Hand Muscles
- Thenar mass: Flexor pollicis brevis, opponens pollicis, adductor pollicis, abductor pollicis brevis control thumb movements.
- Hypothenar mass: Opponens digiti minimi, flexor digiti minimi brevis, abductor digiti minimi control pinky.
- Palmaris brevis tenses the palm's connective tissue.
- Lumbricals flex MCP joints and extend IP joints, forming an "L" shape.
- Palmar interossei adduct fingers (PAD); dorsal interossei abduct fingers (DAB).
Key Terms & Definitions
- Scapula — shoulder blade bone.
- Humerus — upper arm bone.
- Rotator cuff — group of four shoulder-stabilizing muscles: supraspinatus, infraspinatus, teres minor, subscapularis.
- Pronate/Supinate — rotate forearm so palm faces down/up.
- Thenar/Hypothenar — muscle masses at thumb/pinky side of palm.
- Lumbricals — hand muscles that flex MCP and extend IP joints.
- Interossei — muscles between hand bones, controlling finger movement.
Action Items / Next Steps
- Review muscle names and their actions, focusing on origins, insertions, and innervations.
- Practice palpating major muscles on yourself to reinforce learning.
- Watch suggested supplementary videos for deeper understanding of muscle groups.