Insertion at the base of the second metacarpal is a characteristic of which muscle?

Insertion at the base of the second metacarpal is a characteristic of which muscle?

• A. External Oblique
• B. Rectus Abdominis
• C. Internal Oblique
• D. Extensor Carpi Radialis Longus

Answer: (D)

The key idea is linking where a muscle inserts to what it does at the wrist. A insertion at the base of the second metacarpal points to a muscle that acts on the wrist on the radial side. The Extensor Carpi Radialis Longus fits this: it runs from the humerus and attaches to the base of the second metacarpal, allowing wrist extension and radial deviation. The abdominal muscles listed attach to the ribs, linea alba, and pelvis, not to hand bones, so they don’t insert on the metacarpals and aren’t involved in wrist movements. Therefore, this muscle’s insertion location makes it the correct choice.

The key idea is linking where a muscle inserts to what it does at the wrist. A insertion at the base of the second metacarpal points to a muscle that acts on the wrist on the radial side. The Extensor Carpi Radialis Longus fits this: it runs from the humerus and attaches to the base of the second metacarpal, allowing wrist extension and radial deviation. The abdominal muscles listed attach to the ribs, linea alba, and pelvis, not to hand bones, so they don’t insert on the metacarpals and aren’t involved in wrist movements. Therefore, this muscle’s insertion location makes it the correct choice.