19 Muscles of the Anterior Forearm | The Hand
Learning Objectives:
- Identify and describe the joints of the hand.
- Identify and describe the muscles of the anterior forearm.
- Identify and describe the muscles of the hand.
Terms to Know
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Joints of the Hand
Muscles of the Anterior Forearm
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Muscles of the Hand
Other Terms
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Introduction
In this lab, you will review the muscles of the anterior forearm and hand and the joints of the hand.
Lab Activities
Activity 1: Muscles of the Anterior Forearm
The muscles of the anterior compartment, or anterior aspect of the forearm, are generally flexors of the wrist or fingers. The flexors originate from a flexor mass with its proximal attachment point on the medial epicondyle of the humerus. Palpate your medial epicondyle and then move your fingers to the mass just distal to the medial epicondyle. Flex your wrist, and you should feel this flexor mass contract. The anterior compartment also contains pronators of the arm. From anatomical position, this motion would be turning your hand so that your thumb points medially and your hand faces backward. If you imagine holding a glass of water, pronation would also be the motion of turning your wrist and hand to pour the water out of the glass.
The anterior compartment can be divided into three layers. We won’t ask you specifically which layer a muscle is located in. However, sometimes breaking up these muscles into smaller groups can make it easier to learn them.
Before we observe the muscles of the forearm in these layers, you should observe the brachioradialis. This muscle originates in the brachium, or arm, and inserts onto the styloid process of the radius. It looks like the muscles of the forearm, but it doesn’t actually cross the wrist. It assists with flexion of the elbow.
Superficial layer:
- The pronator teres inserts onto the mid-shaft of the radius. It is the shortest muscle originating from the medial epicondyle.
- Flexor carpi radialis and flexor carpi ulnaris cross only the wrist joints and flex the wrist (flexor = flex, and carpi = wrist). Flexor carpi ulnaris inserts on the ulnar side of the wrist and assists with ulnar deviation (wrist adduction). Flexor carpi radialis inserts on the radial side of the wrist and also assists with radial deviation (wrist abduction).
- The palmaris longus is a very small muscle and weak flexor of the wrist. It is not present in 10-20% of the population.
Intermediate Layer:
- Observe flexor digitorum superficialis (FDS). It crosses the wrist, MCP, and PIP joints of digits 2-5 in the hand. Notice how this muscle splits and inserts on the middle phalanx of these digits.
Deep Layer:
- Observe flexor digitorum profundus (FDP). Profundus means “deep,” and this muscle is deep to the flexor digitorum superficialis. Both of these muscles act to flex MCP and PIP joints of the digits. However, the FDP runs deep to the tendon of FDS through its split at the middle phalanx and continues distally to insert on the distal phalanx