Latissimus dorsi muscle

The latissimus dorsi is a broad, flat muscle spanning the lower and middle back to the upper arm. It extends, adducts, and internally rotates the arm at the shoulder.

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Humerus: The long bone of the upper arm, extending from the shoulder to the elbow. The latissimus dorsi inserts into the humerus, transmitting its pull to the arm.
Superficial back muscles: Muscles that connect the upper limb to the trunk or move the scapula, lying over deeper back muscles. The latissimus dorsi is one of the broad superficial muscles connecting trunk and upper limb.
Pull-up: An exercise in which a person raises the body toward a bar by pulling with the arms. The latissimus dorsi helps pull the body upward by extending and adducting the arms.
Pectoralis major: A large chest muscle that adducts and internally rotates the arm and assists shoulder flexion. It shares several shoulder actions with the latissimus dorsi but lies on the front of the chest.
Lumbosacral transitional vertebra: A congenital vertebral variation in which the lowest lumbar vertebra or upper sacral vertebra has features of both regions. Variation in vertebral anatomy can alter the lower attachment pattern described for the muscle.
Thoracolumbar fascia: A strong sheet of connective tissue covering deep back muscles and anchoring muscles of the trunk. The muscle arises partly from this fascia, linking its pull to the lower trunk.
Muscle origin and insertion: The conventional names for a muscle's relatively fixed attachment and its more mobile attachment. Its extensive trunk origins and humeral insertion help explain its line of pull.
Swimming: Locomotion through water using coordinated movements of the limbs and body. The muscle contributes to powerful arm strokes, especially during the pull phase.
Trapezius: A large superficial back muscle that moves and stabilizes the scapula and extends the neck. It overlies part of the latissimus dorsi but primarily acts on the scapula, not the humerus.
Latissimus dorsi avulsion: A traumatic detachment of the latissimus dorsi tendon from its humeral attachment. This uncommon injury directly disrupts the muscle's force transfer to the arm.