Brachial Plexus

Question 1

the brachial plexus is formed by which cervical roots

Answer 1

C5-T1

Question 2

identify the roots of the
Upper
Middle and
Lower Trunks of the Brachial Plexus

Answer 2

Upper: C5-C6
Middle: C7
Lower: C8-T1

Question 3

major Terminal Nerves of Brachial Plexus

Answer 3

Radial: innervates extensor musculature
Ulnar: innervates medial flexors that lie below elbow
Median: innervates lateral flexors that lie below elbow

Question 4

Where is erb’s point

Answer 4

where C5 and C6 come together

Question 5

roots of long thoracic nerve

Answer 5

C5, C6, C7

Question 6

long thoracic nerve innervates the

Answer 6

serratus anterior muscle which pulls the scapula forward

Question 7

Erb’s Palsy

Answer 7

Upper trunk plexopathy

waiter’s tip deficit

Question 8

Lower trunk plexopathies

Answer 8

Klumpke’s Palsy
Produce claw hand wherein the metacarpalphalangeal joints extend and the proximal interphalangeal joints flex, like a claw – it affects both ulnar and distal median nerve musculature, so all fingers are affected!

Thoracic Outlet syndrome
Thoracic outlet syndrome can also cause vascular compression signs, like edema and arm discoloration, from subclavian artery compression.

Question 9

axillary nerve
C5-C6

innervates:

Answer 9

Innervates the
deltoid muscle- responsible for the latter 70 to 80 degrees of arm abduction. Whereas supraspinatus is responsible for the first 20 to 30 degrees of arm abduction.

teres minor, which assists in shoulder external rotation, which makes sense along with the deltoid’s role in shoulder abduction.

Question 10

Musculocutaneous Nerve
C5-C6

innervates:

Answer 10

innervates the biceps brachii (most notably) it is superficial and flex the forearm in supination
The role of the biceps brachii in supination explains why supination is at least partially preserved in radial nerve injury (when the radial-innervated supinator muscle, itself, is weak).

Brachialis muscle, which is deep and flexes the elbow with the forearm in any position.
Coracobrachialis, which is an important anatomical landmark because the axillary nerve penetrates it to run underneath the biceps brachii; it assists the clavicular head of the pectoralis major muscle in shoulder flexion.

Question 11

dorsal scapular nerve
C4-C5

innervates:

Answer 11

Innervates the rhomboid muscles, which pull the scapula toward midline and downward

Question 12

Subclavius nerve
C5-C6

innervates:

Answer 12

The subclavius provides clavicle depression

Question 13

Suprascapular nerve
C5-C6

Innervates:

Answer 13

innervates the supraspinatus muscle (C5, C6), which is responsible for the first 20 to 30 degrees of arm abduction.

Innervates the infraspinatus muscle (C5, C6), which is the primary external rotator of the arm (the other is… teres minor).

Question 14

The pectoral nerves
Lateral pectoral nerve (C5, C6, C7)
Medial pectoral nerve (C8, T1)

Answer 14

Both innervate the pectoralis major muscle, which provides shoulder adduction and shoulder internal rotation.

Lateral pectoral nerve innervates the clavicular head of pectoralis major, which additionally provides shoulder flexion.

Medial pectoral nerve innervates the sternal head of the pectoralis major muscle, which additionally provides shoulder extension.

The pectoral nerves (mostly the medial pectoral nerve) also innervate pectoralis minor, which provides scapula depression.

Question 15

Thoracodorsal nerve

C6, C7, C8

Answer 15

lies along posterior cord interspersed between the upper and lower subscapular nerves
Innervates latissimus dorsi, which provides shoulder adduction.

Question 16

Subscapular nerves

Answer 16

innervate the subscapularis muscle, which assists in shoulder internal rotation.
The lower subscapular nerve also innervates teres major, which assists in shoulder internal rotation

(compare this to teres minor, which assists in shoulder external rotation and is innervated by the axillary nerve)