Which muscles are innervated by the anterior interosseous nerve (AIN)?

• A. Flexor Carpi Ulnaris
• B. Pronator Teres
• C. Flexor Pollicis Longus
• D. Extensor Carpi Radialis Longus

Answer: (C)

The anterior interosseous nerve (AIN), a branch of the median nerve, is primarily responsible for innervating specific deep muscles in the forearm. The correct option highlights the Flexor Pollicis Longus, which is one of its key targets. This muscle plays an essential role in flexing the thumb at the interphalangeal joint.

The AIN innervates the deep flexors in the forearm, which includes the Flexor Pollicis Longus, along with the flexor digitorum profundus for the index and middle fingers, and the pronator quadratus. Its role is crucial for fine motor control and dexterity in the hand, particularly in thumb movements.

In contrast, the other muscles listed do not receive innervation from the AIN. The Flexor Carpi Ulnaris is innervated by the ulnar nerve, while the Pronator Teres is primarily innervated by the median nerve, and the Extensor Carpi Radialis Longus is innervated by the radial nerve. Understanding the specific innervations helps in diagnosing and managing conditions related to nerve injuries and muscle function in the upper limb.