Brachial Plexus Flashcards

Study the brachial plexus roots and trunks, including their formation, cervical relationships, major branches, and clinical injuries.

Card 1 of 30Question

What is the brachial plexus?

A network of nerves formed by the anterior rami of spinal nerves C5 to T1 that supplies the upper limb.

In This Section

1. What is the brachial plexus?

A network of nerves formed by the anterior rami of spinal nerves C5 to T1 that supplies the upper limb.

2. Which spinal nerve roots typically form the brachial plexus?

The anterior rami of C5, C6, C7, C8, and T1.

3. What is the usual structural sequence of the brachial plexus?

Roots, trunks, divisions, cords, and terminal branches.

4. Where do the brachial plexus roots emerge in the neck?

Between the anterior and middle scalene muscles in the interscalene space.

5. Which fascial layer covers the scalene muscles and brachial plexus roots?

The prevertebral layer of deep cervical fascia.

6. What are the three trunks of the brachial plexus?

The superior, middle, and inferior trunks.

7. Which spinal nerve roots unite to form the superior trunk?

C5 and C6.

8. Which spinal nerve root continues as the middle trunk?

C7.

9. Which spinal nerve roots unite to form the inferior trunk?

C8 and T1.

10. In which part of the neck are the brachial plexus trunks primarily located?

The lower posterior cervical triangle, superior to the clavicle.

11. What is the relationship of the brachial plexus trunks to the subclavian artery?

They pass through the interscalene region superior and posterior to the subclavian artery.

12. How is the subclavian vein positioned relative to the anterior scalene muscle?

It passes anterior to the anterior scalene, outside the interscalene triangle.

13. Which nerve arises from the C5 root and commonly receives contributions from C4 and C6?

The dorsal scapular nerve.

14. Which muscles are supplied by the dorsal scapular nerve?

The rhomboid major and minor muscles, with a variable contribution to levator scapulae.

15. Which nerve arises from the C5, C6, and C7 roots of the brachial plexus?

The long thoracic nerve.

16. Which muscle is innervated by the long thoracic nerve?

The serratus anterior muscle.

17. What clinical finding is characteristic of long thoracic nerve injury?

Medial scapular winging caused by serratus anterior weakness.

18. Which two nerves commonly arise from the superior trunk of the brachial plexus?

The suprascapular nerve and nerve to subclavius.

19. Which muscles are supplied by the suprascapular nerve?

The supraspinatus and infraspinatus muscles.

20. Through which scapular opening does the suprascapular nerve pass?

The suprascapular notch, beneath the superior transverse scapular ligament.

21. What is the principal function of the nerve to subclavius?

Motor innervation of the subclavius muscle, which stabilizes and depresses the clavicle.

22. Into which two divisions does each brachial plexus trunk separate?

An anterior division and a posterior division.

23. What is the general muscular distribution of the anterior divisions of the brachial plexus?

They primarily contribute to nerves supplying the anterior, or flexor, muscle compartments of the upper limb.

24. What is the general muscular distribution of the posterior divisions of the brachial plexus?

They primarily contribute to nerves supplying the posterior, or extensor, muscle compartments of the upper limb.

25. What is a prefixed brachial plexus?

A variation with increased contribution from C4 and relatively reduced contribution from T1.

26. What is a postfixed brachial plexus?

A variation with increased contribution from T2 and relatively reduced contribution from C5.

27. Which brachial plexus roots are primarily affected in Erb-Duchenne palsy?

C5 and C6, commonly involving the superior trunk.

28. What characteristic upper limb posture may occur in Erb-Duchenne palsy?

The waiter's tip posture, with shoulder adduction, medial rotation, elbow extension, and forearm pronation.

29. Which brachial plexus roots are primarily affected in Klumpke palsy?

C8 and T1, commonly involving the inferior trunk.

30. Why can an inferior brachial plexus lesion be associated with Horner syndrome?

An associated proximal T1 lesion may interrupt sympathetic fibers destined for the head and neck.