Which nerve innervates the interossei and intrinsic hand muscles, enabling finger abduction and adduction, with sensation to the little finger?

Which nerve innervates the interossei and intrinsic hand muscles, enabling finger abduction and adduction, with sensation to the little finger?

• A. Sciatic nerve
• B. Radial nerve
• C. Ulnar nerve
• D. Median nerve

Answer: (C)

The key concept here is which nerve supplies the muscles that move the fingers together or apart and also provides sensation to the little finger. The interossei (dorsal and palmar) are the muscles that abduct (spread) and adduct (bring together) the fingers. All of these interossei, along with most of the intrinsic hand muscles in the ulnar side of the hand, are innervated by the ulnar nerve (C8–T1). The little finger’s sensation is also carried by the ulnar nerve, which covers the medial one and a half fingers on the palmar side. Other nerves don’t fit both parts. The sciatic nerve is for the leg, so it can’t account for hand muscles or finger sensation. The radial nerve mainly supplies extensor muscles and the back of the hand and doesn’t innervate the interossei or provide sensation specifically to the little finger. The median nerve innervates the lateral (thumb-side) intrinsic muscles and provides sensation to the thumb through the index and middle fingers, not the little finger. So, the ulnar nerve best explains both the motor control of finger abduction/adduction via the interossei and the sensory territory of the little finger.

The key concept here is which nerve supplies the muscles that move the fingers together or apart and also provides sensation to the little finger. The interossei (dorsal and palmar) are the muscles that abduct (spread) and adduct (bring together) the fingers. All of these interossei, along with most of the intrinsic hand muscles in the ulnar side of the hand, are innervated by the ulnar nerve (C8–T1). The little finger’s sensation is also carried by the ulnar nerve, which covers the medial one and a half fingers on the palmar side.

Other nerves don’t fit both parts. The sciatic nerve is for the leg, so it can’t account for hand muscles or finger sensation. The radial nerve mainly supplies extensor muscles and the back of the hand and doesn’t innervate the interossei or provide sensation specifically to the little finger. The median nerve innervates the lateral (thumb-side) intrinsic muscles and provides sensation to the thumb through the index and middle fingers, not the little finger.

So, the ulnar nerve best explains both the motor control of finger abduction/adduction via the interossei and the sensory territory of the little finger.