Spinal Nerve Anatomy

🥼 Practice and Clinical
1

Composition

[[Terminal root]] consists of anterior root and posterior root (the posterior root swelling is the [[spinal ganglion]])
The anterior and posterior roots converge at the intervertebral foramen

Branches


[[Meningeal branch]] — nourishes the vertebrae
[[Communicating branch]] — connects to the sympathetic trunk
[[Posterior branch]] — fine, segmentally distributed (segmentally innervates the skin on both sides beside the spine)
[[Anterior branch]] — except for thoracic nerves which are segmentally distributed, all blend into nerve plexuses

Fiber components

Anterior root — motor (somatic movement, visceral movement)
Posterior root — sensory (somatic sensation, visceral sensation)

Cervical plexus (C1-C4 anterior branches)

Location: deep to the sternocleidomastoid muscle
Branches:

  • Cutaneous branches
    • Lesser occipital nerve
    • Great auricular nerve
    • Transverse cervical nerve
    • Supraclavicular nerve
  • Phrenic branch (mixed branch)
    • Motor fibers innervate the diaphragm
    • Sensory fibers innervate the pleura, pericardium, peritoneum below the diaphragm; the right branch innervates the liver, gallbladder, extrahepatic bile ducts, and their serosa

Brachial plexus (C5-T1 anterior branches)

  • Axillary nerve
    • Muscular branches: deltoid, teres minor
    • Cutaneous branch: lateral superior cutaneous nerve of the arm (outer upper arm)
  • Musculocutaneous nerve
    • Muscular branches: coracobrachialis, brachialis, biceps brachii
    • Cutaneous branch: lateral cutaneous nerve of the forearm
  • Median nerve
    • Articular branches: branches to the elbow joint, intercarpal joint
    • Muscular branches: most of the forearm flexors, thenar muscles (except adductor pollicis), first and second lumbricals
    • Cutaneous branches: palmar half of the radial side + three and a half radial side fingers on the palmar side; the most sensitive area is the thenar regionfiles/Pasted image 20250901110705.png
  • Ulnar nerve
    • Articular branches: branches to the elbow joint, wrist joint
    • Muscular branches: flexor carpi ulnaris, the ulnar half of the flexor digitorum profundus, hypothenar muscles, adductor pollicis, third and fourth lumbricals, interossei muscles, first dorsal interosseous muscle
    • Cutaneous branches: dorsal branch (dorsal side of the ulnar two fingers, palmar side of the ulnar one and a half fingers); the most sensitive area is the lateral edge of the hypothenar
  • Radial nerve
    • Articular branches: branches to elbow joint, wrist joint, proximal radioulnar joint, metacarpophalangeal joint, interphalangeal joint
    • Muscular branches: entire extensor group of the upper limb
    • Cutaneous branches: dorsal side of the radial side of the hand, dorsal side of the two-and-a-half radial fingers