If median nerve is injured at the wrist, then loss of function of all of the following muscles will take place, EXCEPT:
**Core Concept**
The median nerve innervates muscles in the anterior compartment of the forearm, primarily responsible for wrist and finger movements. Injury to the median nerve at the wrist can lead to weakness or paralysis of these muscles, affecting hand function.
**Why the Correct Answer is Right**
The median nerve innervates the thenar muscles (thumb muscles), specifically the opponens pollicis, abductor pollicis brevis, and flexor pollicis brevis, which are responsible for thumb opposition, abduction, and flexion, respectively. These muscles are critical for fine motor activities, such as grasping and manipulating objects. The median nerve also innervates the lumbrical muscles of the fingers (II and III), which are responsible for finger flexion at the metacarpophalangeal joints. In contrast, the ulnar nerve innervates the interosseous muscles and the adductor pollicis muscle, which are responsible for finger spreading and thumb adduction.
**Why Each Wrong Option is Incorrect**
**Option A:** The thenar muscles are indeed innervated by the median nerve, making this option incorrect.
**Option B:** The lumbrical muscles of the fingers (II and III) are also innervated by the median nerve, making this option incorrect.
**Option C:** The adductor pollicis muscle is actually innervated by the ulnar nerve, not the median nerve, making this option correct.
**Clinical Pearl / High-Yield Fact**
The median nerve injury at the wrist can lead to a characteristic "claw hand" deformity due to the paralysis of the intrinsic muscles of the hand, which are responsible for finger flexion and spreading.
**Correct Answer: C. The adductor pollicis muscle is actually innervated by the ulnar nerve, not the median nerve.