Which back muscle inserts on the humerus?

• A. Rhomboid
• B. Trapezius
• C. Latissimus Dorsi
• D. Levator Scapula

Answer: (C)

Muscle insertions determine which bone they move. The back muscle that reaches the humerus is the latissimus dorsi, which attaches at the floor of the intertubercular groove of the humerus. From that position, it can pull the arm down and back, extend the shoulder, and medially rotate the arm. The other muscles attach to the scapula or other regions instead of the humerus—rhomboids to the medial border of the scapula, trapezius to the clavicle and scapula, and levator scapula to the superior angle of the scapula. So the latissimus dorsi is the one that inserts on the humerus.