Final answer:
The long thoracic nerve innervates the serratus anterior muscle, and injury to this nerve can cause weakness in that muscle.
Step-by-step explanation:
The long thoracic nerve is a nerve that originates from the brachial plexus, a network of nerves formed by the anterior rami (branches) of the lower cervical and upper thoracic spinal nerves (C5 to C7). The long thoracic nerve has a specific course and innervates a particular muscle, playing a crucial role in the movement and stability of the shoulder.
The long thoracic nerve innervates the serratus anterior muscle. Injury to the long thoracic nerve can result in weakness of the serratus anterior muscle. Dissection of the axillary lymph nodes or a mastectomy can potentially injure the long thoracic nerve, leading to weakness in this muscle.