All of the following muscles of pollex are supplied by median nerve, EXCEPT?
**Core Concept**
The muscles of the pollex (thumb) are primarily innervated by the median nerve, which is responsible for thumb opposition, flexion, and abduction. This is due to the median nerve's supply to the thenar muscles, specifically the opponens pollicis, abductor pollicis brevis, and flexor pollicis brevis.
**Why the Correct Answer is Right**
The median nerve innervates the thenar muscles, which are crucial for thumb function. The opponens pollicis muscle is responsible for opposition of the thumb, allowing it to touch the other fingers. The abductor pollicis brevis muscle abducts the thumb, moving it away from the palm. The flexor pollicis brevis muscle flexes the thumb, bringing it towards the palm. These muscles are essential for fine motor movements and grasping functions.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the opponens pollicis, abductor pollicis brevis, and flexor pollicis brevis are indeed supplied by the median nerve.
* **Option B:** This option is incorrect because the first dorsal interosseous muscle is actually supplied by the ulnar nerve, not the median nerve.
* **Option C:** This option is incorrect because the adductor pollicis muscle is supplied by the ulnar nerve, not the median nerve.
* **Option D:** This option is incorrect because the flexor pollicis longus muscle is supplied by the anterior interosseous branch of the median nerve, which is part of the median nerve's supply.
**Clinical Pearl / High-Yield Fact**
When examining a patient with median nerve damage, it is essential to assess thumb function, as the median nerve's supply to the thenar muscles can result in weakness or paralysis of the thumb. This can affect a patient's ability to grasp or perform fine motor tasks.
**Correct Answer:** B.