Anatomy Exam Brachial Plexus Structures 3 — Questions and Answers
Question 1: The long thoracic nerve innervates which muscle and arises from which roots?
- Serratus anterior; C5, C6, C7 (Correct answer)
- Subscapularis; C5, C6
- Trapezius; C3, C4
- Rhomboids; C4, C5
Correct answer: Serratus anterior; C5, C6, C7
The long thoracic nerve (of Bell) arises from C5, C6, C7 roots and innervates the serratus anterior.
Question 2: The thoracodorsal nerve innervates the latissimus dorsi and arises from which cord?
- Posterior cord (Correct answer)
- Medial cord
- Lateral cord
- Upper trunk
Correct answer: Posterior cord
The thoracodorsal nerve is a branch of the posterior cord (C6–C8) and innervates the latissimus dorsi.
Question 3: Which nerve arises from the posterior cord and supplies the teres major and subscapularis?
- Lower subscapular nerve (Correct answer)
- Upper subscapular nerve
- Axillary nerve
- Thoracodorsal nerve
Correct answer: Lower subscapular nerve
The lower subscapular nerve (C5–C6) innervates both teres major and the lower portion of subscapularis.
Question 4: A patient has loss of sensation over the medial arm. Which nerve is most likely injured?
- Medial cutaneous nerve of the arm (Correct answer)
- Medial cutaneous nerve of the forearm
- Intercostobrachial nerve
- Medial cord
Correct answer: Medial cutaneous nerve of the arm
The medial cutaneous nerve of the arm (medial brachial cutaneous nerve) provides sensation to the medial surface of the arm.
Question 5: Which division-level structure of the brachial plexus is located posterior to the clavicle?
- Divisions (Correct answer)
- Trunks
- Cords
- Terminal branches
Correct answer: Divisions
The divisions of the brachial plexus lie posterior to the clavicle, between the trunks and cords.
Question 6: The medial pectoral nerve and lateral pectoral nerve together innervate which muscles?
- Pectoralis major and pectoralis minor (Correct answer)
- Pectoralis major only
- Pectoralis minor only
- Subclavius and pectoralis major
Correct answer: Pectoralis major and pectoralis minor
The lateral pectoral nerve innervates pectoralis major; the medial pectoral nerve innervates pectoralis minor and pectoralis major.
Question 7: Which brachial plexus root contributes to both the phrenic nerve and the brachial plexus?
- C5 (Correct answer)
- C6
- C7
- C8
Correct answer: C5
C5 contributes to the phrenic nerve (along with C3 and C4) and is also the most superior root of the brachial plexus.
Anatomy Exam Brachial Plexus Structures 3
The long thoracic nerve innervates which muscle and arises from which roots?