Physical Therapy Assistant Practice Exam

Which nerve is responsible for innervating the serratus anterior muscle?

1. Accessory nerve

2. Long thoracic nerve

3. Dorsal scapular nerve

4. Thoracodorsal nerve

The correct answer is: Long thoracic nerve

The long thoracic nerve is the key nerve responsible for innervating the serratus anterior muscle, which plays a crucial role in the movement and stabilization of the scapula. This muscle is essential for actions such as protraction of the scapula and upward rotation, particularly during overhead arm movements. The long thoracic nerve emerges from the brachial plexus, specifically from the ventral rami of the C5, C6, and C7 spinal nerves. Its course runs laterally along the thorax, innervating the serratus anterior muscle, and is pivotal for shoulder function. Weakness or injury to the long thoracic nerve can lead to conditions like "winging" of the scapula, where the medial border protrudes away from the thoracic wall, significantly impacting a person's ability to perform overhead activities. Other nerves mentioned play different roles: the accessory nerve primarily innervates the sternocleidomastoid and trapezius muscles, the dorsal scapular nerve innervates the rhomboids and levator scapulae, and the thoracodorsal nerve innervates the latissimus dorsi muscle. Each of these innervations contributes to upper body movement but does not directly affect the