Which of the following lists contains the muscles that contribute to wrist flexion?

Which of the following lists contains the muscles that contribute to wrist flexion?

• A. Abductor pollicis longus
• B. Flexor carpi radialis, flexor pollicis longus, flexor digitorum superficialis, flexor digitorum profundus, flexor carpi ulnaris, and palmaris longus
• C. Extensor carpi radialis longus and brevis
• D. Flexor carpi radialis and extensor carpi ulnaris only

Answer: (B)

Wrist flexion comes from forearm flexor muscles that cross the wrist on the anterior side. The primary wrist flexors are flexor carpi radialis and flexor carpi ulnaris, and other muscles that cross the wrist also contribute: flexor digitorum superficialis and flexor digitorum profundus (which flex the fingers and assist the wrist when the fingers are flexed), palmaris longus (which tenses the palmar fascia and helps flex the wrist), and flexor pollicis longus (which flexes the thumb but also crosses the wrist and adds to wrist flexion). So the list that includes all of these muscles—flexor carpi radialis, flexor pollicis longus, flexor digitorum superficialis, flexor digitorum profundus, flexor carpi ulnaris, and palmaris longus—is the correct one. In contrast, muscles that extend the wrist or abduct it (such as extensor carpi radialis longus and brevis, extensor carpi ulnaris, and abductor pollicis longus) do not contribute to wrist flexion.

Wrist flexion comes from forearm flexor muscles that cross the wrist on the anterior side. The primary wrist flexors are flexor carpi radialis and flexor carpi ulnaris, and other muscles that cross the wrist also contribute: flexor digitorum superficialis and flexor digitorum profundus (which flex the fingers and assist the wrist when the fingers are flexed), palmaris longus (which tenses the palmar fascia and helps flex the wrist), and flexor pollicis longus (which flexes the thumb but also crosses the wrist and adds to wrist flexion).

So the list that includes all of these muscles—flexor carpi radialis, flexor pollicis longus, flexor digitorum superficialis, flexor digitorum profundus, flexor carpi ulnaris, and palmaris longus—is the correct one. In contrast, muscles that extend the wrist or abduct it (such as extensor carpi radialis longus and brevis, extensor carpi ulnaris, and abductor pollicis longus) do not contribute to wrist flexion.