American Board of Surgery Qualifying Exam (ABS QE) Practice Test

Which nerve provides innervation to the pectoralis major from a lateral position?

1. Medial pectoral nerve

2. Lateral pectoral nerve

3. Thoracodorsal nerve

4. Intercostal nerve

The correct answer is: Lateral pectoral nerve

The lateral pectoral nerve is primarily responsible for innervating the pectoralis major muscle from a lateral position. This nerve originates from the lateral cord of the brachial plexus and specifically supplies the clavicular head of the pectoralis major, which plays an essential role in shoulder flexion, adduction, and medial rotation. The anatomical relevance lies in its pathway; the lateral pectoral nerve travels laterally towards the pectoralis major muscle, ensuring that it can effectively carry motor signals to this muscle. Understanding the anatomical routes of these nerves provides crucial insights into their function and the intricate connections within the brachial plexus. In contrast, while the medial pectoral nerve also innervates the pectoralis major, it primarily targets the sternocostal head and approaches the muscle from a medial aspect. The thoracodorsal nerve mainly innervates the latissimus dorsi, serving a different area entirely. Additionally, the intercostal nerves provide sensory innervation to the thoracic wall and do not facilitate the motor control of the pectoralis major. Knowing these distinctions highlights the specific pathway and role of the lateral pectoral nerve in muscle innervation.