|
Year |
2007 |
|---|---|
|
Question Number |
49 |
|
Category |
Shoulder and Elbow |
Question
What is the innervation of the muscle that appears to be disrupted in the patient shown in Figure 15?
1- Lateral pectoral
2- Axillary
3- Musculocutaneous
4- Upper subscapular
5- Lower subscapular
Figures
Answer (click for answer)
The correct answer is 1 – Lateral pectoral (lateral anterior thoracic n.)
The patient has a drooping right pec muscle. The pectoralis major muscle is innervated by the medial and lateral pectoral nerves. The lateral nerve is larger and arises from the lateral cord of the brachial plexus. It is composed of nerves from C5, C6, and C7.
The axillary n (C5-6) is the terminal branch of the posterior cord and innervates the deltoid and teres minor. The Musculocutaneous n (C5-7) arises from the lateral cord and innervates the coracobrachialis, biceps brachii, and brachialis; it continues as the lateral antebrachial cutaneous nerve. The upper subscapular n (C5-6) arises as a branch of the posterior cord and innervates the superior part of the subscapularis. The lower subscapular n (C5-6) arises as a branch of the posterior cord and innervates the inferior portion of the subscap and teres major.
Reference:
