Which muscle is the longest in the human body?

• A. Rectus abdominis
• B. Gracilis
• C. Biceps femoris
• D. Sartorius

Answer: (D)

The longest muscle is the one that travels the greatest distance from its origin to its insertion while crossing joints. The sartorius runs from the anterior superior iliac spine of the pelvis down across the thigh to the inner tibia, crossing both the hip and knee joints. This long, diagonal path across the thigh makes it longer than the other muscles listed. The rectus abdominis sits in the abdomen, the gracilis is a shorter, inner-thigh muscle, and the biceps femoris is a long hamstring on the back of the thigh—none span as far from hip to knee as the sartorius.