Certified Surgical First Assistant (CSFA) Practice Test

Which nerve innervates the latissimus dorsi muscle?

1. Femoral nerve

2. Thoracodorsal nerve

3. Median nerve

4. Radial nerve

The correct answer is: Thoracodorsal nerve

The latissimus dorsi muscle is primarily innervated by the thoracodorsal nerve, which is a branch of the posterior cord of the brachial plexus. The thoracodorsal nerve arises from the C6, C7, and C8 spinal nerves. This muscle plays a crucial role in various upper body movements, including adduction, extension, and internal rotation of the arm. Because it is innervated by the thoracodorsal nerve, injury to this nerve could significantly impact a person's ability to perform these movements effectively. In contrast, the other nerves listed are associated with different muscle groups or functions and do not innervate the latissimus dorsi. For instance, the femoral nerve primarily innervates the quadriceps and other muscles of the anterior thigh, while the median nerve is involved with flexor muscles in the forearm and hand. The radial nerve mainly innervates muscles in the posterior aspect of the arm and forearm, which are responsible for extension. Thus, the thoracodorsal nerve is specifically linked to the function and movement of the latissimus dorsi, making it the correct answer.