Anatomy Exam Brachial Plexus Structures 2 — Questions and Answers
Question 1: Which roots of the brachial plexus form the upper trunk?
- C5 and C6 (Correct answer)
- C6 and C7
- C7 and C8
- C8 and T1
Correct answer: C5 and C6
The upper trunk is formed by the union of the C5 and C6 ventral rami.
Question 2: The suprascapular nerve arises from which part of the brachial plexus?
- Upper trunk (Correct answer)
- Middle trunk
- Posterior cord
- Lateral cord
Correct answer: Upper trunk
The suprascapular nerve branches directly from the upper trunk before cord formation.
Question 3: Which nerve of the brachial plexus is most commonly injured in a posterior shoulder dislocation?
- Axillary nerve (Correct answer)
- Radial nerve
- Musculocutaneous nerve
- Suprascapular nerve
Correct answer: Axillary nerve
The axillary nerve is most vulnerable in shoulder dislocations due to its proximity to the surgical neck of the humerus.
Question 4: The medial cutaneous nerve of the forearm is a direct branch of which cord?
- Medial cord (Correct answer)
- Lateral cord
- Posterior cord
- Middle trunk
Correct answer: Medial cord
The medial cutaneous nerve of the forearm arises directly from the medial cord of the brachial plexus.
Question 5: Which terminal branch of the brachial plexus carries fibers exclusively from C5 and C6?
- Musculocutaneous nerve (Correct answer)
- Median nerve
- Ulnar nerve
- Radial nerve
Correct answer: Musculocutaneous nerve
The musculocutaneous nerve is derived from C5–C7 but its motor contribution to the flexors is predominantly C5–C6.
Question 6: In Klumpke's palsy, which roots of the brachial plexus are injured?
- C8 and T1 (Correct answer)
- C5 and C6
- C6 and C7
- C7 and C8
Correct answer: C8 and T1
Klumpke's palsy results from injury to the lower trunk (C8–T1), causing intrinsic hand muscle weakness.
Question 7: Which brachial plexus cord lies medial to the axillary artery in the axilla?
- Medial cord (Correct answer)
- Lateral cord
- Posterior cord
- All three cords surround it equally
Correct answer: Medial cord
The medial cord lies on the medial side of the axillary artery, while the lateral cord is lateral and the posterior cord is posterior.
Anatomy Exam Brachial Plexus Structures 2
Which roots of the brachial plexus form the upper trunk?