The insertion of the extensor carpi radialis longus muscle is on which of the following bones or structures?

• A. The base of the second metacarpal
• B. The styloid process of the radius
• C. The lateral epicondyle of the humerus
• D. The olecranon process of the ulna

Answer: (A)

Verified step by step guidance

1. Step 1: Begin by identifying the extensor carpi radialis longus muscle. This muscle is part of the posterior compartment of the forearm and is responsible for extending and abducting the wrist.
2. Step 2: Understand the concept of muscle insertion. The insertion is the point where the muscle attaches to the bone or structure that moves when the muscle contracts. For the extensor carpi radialis longus, this is crucial to determine its function.
3. Step 3: Recall the anatomical location of the base of the second metacarpal. This is a bone in the hand, specifically the second metacarpal, which corresponds to the index finger. The extensor carpi radialis longus inserts here to facilitate wrist extension and abduction.
4. Step 4: Eliminate the other options by understanding their anatomical relevance. The styloid process of the radius, lateral epicondyle of the humerus, and olecranon process of the ulna are not insertion points for this muscle. Instead, they serve as attachment points for other muscles or structures.
5. Step 5: Confirm the correct answer by reviewing the muscle's function and insertion point. The extensor carpi radialis longus inserts at the base of the second metacarpal, allowing it to perform its role in wrist movement.