What is the origin of the latissimus dorsi?

• A. Spinous processes of T7-L5, thoracolumbar fascia, iliac crest, and inferior ribs 9-12
• B. Clavicle
• C. Scapula
• D. Spinous processes of T2-T6

Answer: (A)

The latissimus dorsi has a broad, powerful origin from the lower trunk of the back, which helps it cover a large area before its tendon reaches the arm. It starts from spinous processes of the lower thoracic to lumbar spine (around T7 down to L5), continues through the thoracolumbar fascia, attaches to the iliac crest, and also connects to the inferior ribs (9–12). This widespread origin explains why the muscle can generate strong extension, adduction, and medial rotation of the humerus, especially when the arm is pulled downward or when the trunk helps drive the movement.

It doesn’t arise from the clavicle or scapula, and a small, upper-thoracic origin (like only T2–T6) wouldn’t provide the same broad attachment pattern needed for its actions. The thoracolumbar fascia and iliac crest connections are key features that differentiate this muscle’s origin from other back or shoulder muscles.