Which muscles and area are innervated by the C5 nerve root?

Which muscles and area are innervated by the C5 nerve root?

• A. Deltoid and biceps; shoulder and upper arm
• B. Triceps and forearm; elbow and forearm sensation
• C. Hand intrinsic muscles
• D. Hip flexors

Answer: (A)

C5 mainly supplies shoulder function and the upper arm. The deltoid muscle, which abducts the shoulder, and the biceps muscle, which flexes the elbow and helps with forearm supination, are driven by C5 via the axillary and musculocutaneous nerves, respectively. Sensory fibers from this root cover the shoulder region and the lateral aspect of the upper arm. So the pairing of deltoid and biceps with shoulder and upper arm sensation fits C5. In contrast, the triceps and forearm are primarily innervated by branches that include C7-C8; hand intrinsic muscles are mainly C8–T1; and hip flexors come from L2–L4, not C5.

C5 mainly supplies shoulder function and the upper arm. The deltoid muscle, which abducts the shoulder, and the biceps muscle, which flexes the elbow and helps with forearm supination, are driven by C5 via the axillary and musculocutaneous nerves, respectively. Sensory fibers from this root cover the shoulder region and the lateral aspect of the upper arm. So the pairing of deltoid and biceps with shoulder and upper arm sensation fits C5.

In contrast, the triceps and forearm are primarily innervated by branches that include C7-C8; hand intrinsic muscles are mainly C8–T1; and hip flexors come from L2–L4, not C5.