Spinal nerve root

C8

Muscle contributions

Follow the branches from the spine toward their muscle targets. These are parallel pathways, not a chain in which one muscle innervates the next. Most muscles receive more than one root.

Dorsal ramus · near the spine

• Regional intrinsic back and posterior neck fascicles; individual C8 muscle-to-fascicle assignments are not resolved by the reviewed sources
• Levatores costarum (corresponding fascicles)

Direct anterior-ramus branches · neck

• Middle scalene
• Posterior scalene

Medial pectoral nerve

• Pectoralis minor
• Pectoralis major (sternocostal portion)

Thoracodorsal nerve

• Latissimus dorsi

Radial nerve · arm and elbow

• Triceps brachii (long, lateral and medial heads)
• Anconeus

Deep radial branch · proximal forearm

• Extensor carpi radialis brevis

Posterior interosseous nerve · forearm

• Extensor digitorum
• Extensor digiti minimi
• Extensor carpi ulnaris
• Abductor pollicis longus
• Extensor pollicis longus
• Extensor pollicis brevis
• Extensor indicis

Median nerve · forearm

• Palmaris longus (when present)
• Flexor digitorum superficialis

Median → anterior interosseous nerve

• Flexor digitorum profundus (lateral part, digits 2–3)
• Flexor pollicis longus
• Pronator quadratus

Median → recurrent and digital branches · hand

• Abductor pollicis brevis
• Opponens pollicis
• Flexor pollicis brevis (superficial head)
• Lumbricals 1–2

Ulnar nerve · forearm

• Flexor carpi ulnaris
• Flexor digitorum profundus (medial part, digits 4–5)

Ulnar → deep branch · hand

• Abductor digiti minimi
• Flexor digiti minimi brevis
• Opponens digiti minimi
• Adductor pollicis
• Flexor pollicis brevis (deep head)
• Lumbricals 3–4
• Dorsal interossei (four)
• Palmar interossei (usually three)

Ulnar → superficial branch · hand

• Palmaris brevis