Muscle
Latissimus dorsi
Broad back muscle that pulls on the upper arm
High-yield
Its main shoulder actions are extension, adduction and inward rotation. Both its principal nerve and artery are named thoracodorsal.
Overview
Latissimus gathers a wide attachment across the lower trunk into a tendon on the humerus. It draws a raised arm down and backward; with the hands fixed, it can help lift the body toward them.
Reference facts
- Origin
- Lower thoracic spinous processes, usually T7–T12; thoracolumbar fascia, posterior iliac crest and lower 3–4 ribs; sometimes the inferior scapular angle
- Insertion
- Floor of the humeral intertubercular groove
- Action
- Extends, adducts and internally rotates the arm; helps raise the trunk when the hands are fixed overhead
- Innervation
- Thoracodorsal nerve, C6–C8
- Blood supply
- Mainly the thoracodorsal artery, with additional intercostal and lumbar branches
Mnemonic
Map the humeral groove from lateral to medial: pectoralis major at one lip, latissimus on the floor, teres major at the other lip.
Clinical correlation
Its broad tissue coverage and thoracodorsal vascular supply make it useful in reconstructive flaps. Damage to the accompanying nerve can weaken the muscle's pulling actions.
Frequently asked questions
What does the latissimus dorsi do?
Extends, adducts and internally rotates the arm; helps raise the trunk when the hands are fixed overhead.
What nerve innervates the latissimus dorsi?
The latissimus dorsi is innervated by the thoracodorsal nerve, C6–C8.
Where does the latissimus dorsi attach?
Origin: Lower thoracic spinous processes, usually T7–T12; thoracolumbar fascia, posterior iliac crest and lower 3–4 ribs; sometimes the inferior scapular angle. Insertion: Floor of the humeral intertubercular groove.
What is the blood supply of the latissimus dorsi?
Mainly the thoracodorsal artery, with additional intercostal and lumbar branches.