What is the origin of latissimus dorsi?

• A. Clavicle and sternum.
• B. Spinous processes of T7-L5, thoracolumbar fascia, iliac crest, and lower ribs.
• C. Proximal humerus.
• D. Scapular spine.

Answer: (B)

The main idea is where this wide back muscle attaches to the body before it tacks onto the upper arm. Latissimus dorsi originates from a combination of posterior structures: the spinous processes of the lower thoracic and lumbar vertebrae (often around T7–L5), the thoracolumbar fascia, the iliac crest, and the lower ribs. This broad set of origins gives the muscle a strong, low-to-high line of pull that travels upward to insert into the intertubercular groove of the humerus. From there, it functions to extend, adduct, and medially rotate the arm, and it helps pull the body upward when the arm is fixed.

Clavicle and sternum belong to the pectoralis major, not the latissimus dorsi. The proximal humerus is where the latissimus dorsi inserts, not where it originates. The scapular spine is associated with other muscles like the trapezius or deltoid, not latissimus dorsi.