Overview of Upper Limb Muscles

Introduction

• Commonly known muscles: biceps, triceps, deltoids
• Deep-dive into regions and groups of the upper limb muscles
• Focus areas: shoulder, arm, forearm, and hand
• Main actions and anatomical relations

Shoulder Muscles

Superficial Muscle

• Deltoid: Major arm abductor; shaped like the Greek letter Delta

Deep Muscles (Rotator Cuff)

• Supraspinatus: Located in the supraspinous fossa
• Infraspinatus: Located in the infraspinous fossa
• Teres Minor: Located inferior to infraspinatus
• Subscapularis: Located on the anterior surface of the scapula
• Mnemonic (SITS): Supraspinatus, Infraspinatus, Teres Minor, Subscapularis

Other Muscle

• Teres Major: Inserts lower on the humerus, not part of the rotator cuff

Movements

• Deltoid: Major abductor
• Rotator Cuff: Internal and external rotation

Arm Muscles

Anterior Compartment

• Biceps Brachii: Two heads (long and short), acts on shoulder and elbow joints
• Coracobrachialis: Originates from the coracoid process, acts on shoulder joint
• Brachialis: Main flexor of the forearm at the elbow

Posterior Compartment

• Triceps Brachii: Three heads (long, lateral, medial), extends the arm and forearm

Movements

• Anterior muscles: Flexors of the arm and forearm, some also assist in adduction and supination
• Posterior muscle: Extension of the arm and forearm

Forearm Muscles

Anterior Compartment (Superficial)

• Pronator Teres: Inserts on the radius, involved in pronation
• Flexor Carpi Radialis: Flexes carpal bones of the hand
• Palmaris Longus: Variable presence, inserts on palm ligaments
• Flexor Carpi Ulnaris: Flexes carpal bones on the ulnar side
• Flexor Digitorum Superficialis: Deepest superficial muscle, flexes digits

Anterior Compartment (Deep)

• Flexor Pollicis Longus
• Flexor Digitorum Profundus
• Pronator Quadratus: Deepest, square-shaped muscle, involved in pronation

Movements

• Primarily flexors of the forearm, hand, and digits
• Medial/Lateral muscles: Aid in abduction and adduction
• Pronators: Produce twisting (pronation) motions

Posterior Compartment (Superficial)

• Brachioradialis: Flexes forearm, innervated by radial nerve
• Extensor Carpi Radialis Longus & Brevis: Extends hand, abducts
• Extensor Digitorum: Extends digits
• Extensor Digiti Minimi: Extends little finger
• Extensor Carpi Ulnaris: Extends hand, adducts

Posterior Compartment (Deep)

• Extensor Pollicis Longus & Brevis
• Abductor Pollicis Longus
• Extensor Indicis
• Supinator: Produces supination at the radioulnar joints

Movements

• Primarily extensors of the forearm, hand, and digits
• Supinator: Produces supination

Hand Muscles

Intrinsic Muscles

• Dorsal Interossei: Abduct fingers
• Palmar Interossei: Adduct fingers
• Lumbricals: Flex metacarpophalangeal joints, extend interphalangeal joints
• Hypothenar Muscles: Abductor digiti minimi, flexor digiti minimi, opponens digiti minimi, palmaris brevis
• Thenar Muscles: Abductor pollicis brevis, adductor pollicis, flexor pollicis brevis, opponens pollicis

Extrinsic Muscles

• Originating from arm/forearm, inserting into hand

Movements

• Together perform fine motor movements, complex finger and thumb actions

Clinical Note: Rotator Cuff Injury

Types

• Tendonitis
• Bursitis
• Strains: Overstretching or tearing of tendons

Symptoms

• Pain on lifting/rotating arm
• Swelling
• Shoulder joint stiffness

Treatment

• Rest, ice, NSAIDs
• Strengthening exercises
• Surgery if necessary

Summary

• Shoulder Muscles: Deltoid, Rotator Cuff (SITS), Teres Major
• Arm Muscles: Anterior (Biceps, Coracobrachialis, Brachialis), Posterior (Triceps)
• Forearm Muscles: Anterior (Pronator Teres, Flexors), Posterior (Extensors)
• Hand Muscles: Intrinsic (Interossei, Lumbricals, Thenar, Hypothenar)
• Rotator Cuff Injuries: Symptoms, causes, treatment