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Structure

Muscles of the upper limb

Not medically reviewed · Content last updated · 2 min read ·

This is the date the draft was written, not a medical review date.

The upper limb muscles are grouped by region (shoulder, arm, forearm, hand), and nearly all are supplied by branches of the brachial plexus. Their organisation by compartment and nerve explains most patterns of weakness after nerve injury.

Terminologia Anatomica (Latin): Musculi membri superioris · Open in the 3D atlas

Location

Shoulder: deltoid, rotator cuff, teres major. Arm: anterior flexor compartment and posterior extensor compartment. Forearm: anterior (flexor-pronator) and posterior (extensor-supinator) compartments. Hand: thenar, hypothenar, lumbricals and interossei.

Structure

Arm: biceps, brachialis and coracobrachialis (musculocutaneous nerve); triceps (radial nerve). Forearm flexors: median nerve (except flexor carpi ulnaris and the medial half of flexor digitorum profundus: ulnar); extensors and supinator: radial nerve (posterior interosseous branch). Hand: the ulnar nerve supplies most intrinsic muscles; the median nerve supplies the thenar muscles (abductor pollicis brevis, flexor pollicis brevis, opponens) and lateral two lumbricals (LOAF).

Blood supply

Axillary and brachial arteries (with profunda brachii) supply the shoulder and arm; radial and ulnar arteries, with the anterior and posterior interosseous arteries, supply the forearm; the superficial and deep palmar arches supply the hand. Collateral anastomoses at the shoulder and elbow maintain flow after proximal ligation.

Innervation

Axillary (deltoid, teres minor), suprascapular (supraspinatus, infraspinatus), musculocutaneous (arm flexors), radial (all extensors), median (most forearm flexors, thenar) and ulnar (flexor carpi ulnaris, hypothenar, interossei) nerves. Roots: C5-C6 shoulder and elbow flexion, C7 elbow extension, C8-T1 hand intrinsics (approximate myotomes).

Function

Shoulder muscles position the arm in space; the biceps and brachialis flex the elbow, the triceps extends it; forearm muscles produce wrist movement, pronation-supination and finger flexion and extension; intrinsic hand muscles produce fine grip, precision pinch and opposition of the thumb.

Clinical correlations

Radial nerve injury gives wrist drop; median nerve injury gives weak thumb opposition and the hand of benediction (high lesions) with carpal tunnel syndrome as the commonest entrapment; ulnar nerve injury gives claw hand and loss of finger abduction and adduction. Erb palsy (C5-C6) and Klumpke palsy (C8-T1) reflect upper and lower brachial plexus injury. Compartment syndrome may follow forearm fractures.

Common exam points

  • Musculocutaneous nerve: coracobrachialis, biceps, brachialis (anterior arm). Radial nerve: triceps and all extensors.
  • Median nerve: LOAF muscles (lateral two lumbricals, opponens pollicis, abductor pollicis brevis, flexor pollicis brevis).
  • Ulnar nerve: flexor carpi ulnaris, medial half of flexor digitorum profundus, hypothenar, interossei, adductor pollicis.
  • Wrist drop (radial), ape hand/hand of benediction (median), claw hand (ulnar).
  • Axillary nerve: deltoid and teres minor; sensation over the regimental badge area.

References

  1. Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. Elsevier — Tier 3 (textbook)
  2. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. Wolters Kluwer, 8th edition (2018) — Tier 3 (textbook)
  3. Netter FH. Atlas of Human Anatomy. Elsevier — Tier 3 (textbook)

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