Lats

Lats (Latissimus Dorsi)

The latissimus dorsi, commonly known as "lats," is a broad, flat muscle that covers most of the lower posterior thorax (lower back). It originates from the lower six thoracic vertebral spinous processes, the thoracolumbar fascia (connecting to lumbar and sacral spinous processes), the posterior iliac crest, and the lower three to four ribs. The muscle fibers converge towards the armpit and insert onto the intertubercular groove of the humerus (upper arm bone).

The lats are primarily responsible for movements of the upper extremity, including adduction (moving the arm towards the body), extension (moving the arm backward), and medial (internal) rotation of the arm at the shoulder joint. They also play a significant role in movements such as climbing, rowing, and swimming. Additionally, the latissimus dorsi can act as an accessory muscle of respiration, assisting with deep inspiration and forceful respiratory functions like coughing and sneezing.