Which action is primarily performed by the biceps brachii muscle?

• A. Elbow extension
• B. Shoulder abduction
• C. Wrist flexion
• D. Elbow flexion and forearm supination

Answer: (D)

Verified step by step guidance

1. Step 1: Identify the anatomical location and attachments of the biceps brachii muscle. It originates from the scapula and inserts on the radius bone of the forearm.
2. Step 2: Understand the primary movements produced by the biceps brachii. Since it crosses the elbow joint anteriorly, it mainly acts to flex the elbow.
3. Step 3: Recognize that the biceps brachii also attaches to the radius, which allows it to perform forearm supination (rotating the palm upward).
4. Step 4: Differentiate between elbow flexion and extension. Extension is performed by muscles like the triceps brachii, not the biceps brachii.
5. Step 5: Note that shoulder abduction and wrist flexion are actions performed by other muscles, so the primary actions of the biceps brachii are elbow flexion and forearm supination.