a. Name two forearm muscles that are powerful extensors and abductors of the hand.
b. Name the sole forearm muscle that can flex the distal interphalangeal joints.

Verified step by step guidance

1. For part (a), recall that forearm muscles involved in extension and abduction of the hand are primarily located in the posterior compartment of the forearm. Identify muscles that extend the wrist and also abduct the hand (move it away from the midline).
2. Two key muscles that fit this description are the extensor carpi radialis longus and extensor carpi radialis brevis. Both are powerful wrist extensors and contribute to abduction of the hand.
3. For part (b), focus on the muscles that flex the fingers, specifically those that can flex the distal interphalangeal (DIP) joints, which are the joints closest to the fingertips.
4. The sole forearm muscle capable of flexing the DIP joints is the flexor digitorum profundus. This muscle inserts on the distal phalanges and allows flexion at the DIP joints.
5. Summarize your answers by naming the two muscles for part (a) and the single muscle for part (b), ensuring you understand their anatomical locations and functions.

Key Concepts

Forearm Muscle Functions

Forearm muscles control movements of the wrist, hand, and fingers. Extensors increase the angle at joints (extension), while abductors move the hand away from the midline. Understanding these functions helps identify muscles responsible for specific hand movements.

Extensor and Abductor Muscles of the Hand

Muscles like the extensor carpi radialis longus and brevis are powerful extensors and abductors of the hand. They extend the wrist and move the hand laterally, playing key roles in hand positioning and grip.

Flexion of Distal Interphalangeal Joints

The flexor digitorum profundus is the sole forearm muscle that flexes the distal interphalangeal joints of the fingers. This deep muscle allows bending of the fingertip joints, essential for fine motor skills like gripping small objects.