Segmental Innervation to Muscles of Upper Limbs

The segmental innervation to the muscles of the upper limbs has a proximal—distal gradient, i.e., the more proximal muscles are innervated by the higher segments (C5 and C6) and the more distal muscles are innervated by the lower segments (C8 and Tl). Therefore, the intrinsic shoulder muscles are innervated by C5 and C6, the intrinsic hand muscles are innervated by C8 and Tl, the distal arm and proximal forearm muscles are innervated by C6 and C7, and the more distal forearm muscles are innervated by C7 and C8.

SENSORY INNERVATION

The sensory innervation of the hand is summarized in Figure III-4-2.

Anterior (palmar) Posterior (dorsal)

Anterior (palmar) Posterior (dorsal)

Median n.

Figure 111-4-2. Sensory Innervation of the Hand

Median n.

Figure 111-4-2. Sensory Innervation of the Hand

NERVE INJURIES

Remember: Follow clues in the questions as to the location of the injury. An injury will manifest in symptoms distal to the site of injury.

Example: Radial nerve cut at the wrist. Sensory loss on the dorsum of the hand. No muscular loss as these are already innervated above the site of the lesion.

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