Which of the following is a primary action of the biceps brachii muscle?

• A. Abduction of the arm at the shoulder
• B. Adduction of the arm at the shoulder
• C. Extension of the forearm at the elbow
• D. Flexion of the forearm at the elbow

Answer: (D)

Verified step by step guidance

1. Understand the anatomy of the biceps brachii muscle: The biceps brachii is a two-headed muscle located in the upper arm. It originates from the scapula and inserts into the radius bone of the forearm. Its primary function is related to movements of the forearm and elbow joint.
2. Identify the types of movements possible at the elbow joint: The elbow joint allows for flexion (bending the forearm toward the upper arm) and extension (straightening the forearm away from the upper arm). The biceps brachii is primarily involved in flexion.
3. Analyze the role of the biceps brachii in flexion: When the biceps brachii contracts, it pulls on the radius bone, causing the forearm to move closer to the upper arm, which is the action of flexion.
4. Eliminate incorrect options: Abduction and adduction refer to movements at the shoulder joint, not the elbow. Extension of the forearm is performed by the triceps brachii, not the biceps brachii.
5. Conclude that the primary action of the biceps brachii muscle is flexion of the forearm at the elbow, as this is its main function during contraction.