Which of the following best describes the primary action of the highlighted muscle, the biceps brachii?

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

Answer: (A)

Verified step by step guidance

1. Step 1: Begin by identifying the anatomical location and function of the biceps brachii. The biceps brachii is a two-headed muscle located in the anterior compartment of the upper arm.
2. Step 2: Understand the primary action of the biceps brachii. Its main function is flexion of the forearm at the elbow joint, as it crosses the elbow joint and attaches to the radius via the bicipital aponeurosis and radial tuberosity.
3. Step 3: Consider the secondary actions of the biceps brachii. It also assists in supination of the forearm (rotating the forearm so the palm faces upward) due to its attachment to the radius.
4. Step 4: Evaluate the options provided in the question. Flexion of the forearm at the elbow is the primary action of the biceps brachii, while adduction, abduction, and extension involve other muscles such as the deltoid, triceps brachii, or pectoralis major.
5. Step 5: Confirm your understanding by visualizing or referencing the muscle's anatomy and its role in elbow movement. This ensures clarity in identifying the correct action associated with the biceps brachii.