Upper Limb Part 2- Brachial Plexus

Question 1

Anterior rami splits into

Answer 1

Anterior division (flexors) 
Posterior division (extensors)

Question 2

Upper limb receives most of its innervation from spinal segments

Answer 2

C5-T1

Question 3

Proximal muscles tend to be innervated by

While distal muscles tend to be innervated by more

Answer 3

More superior nerve segments (C5,6)

Inferior nerve segments (C8-T1)

Question 4

Composition of the brachial plexus

Answer 4

C5-T1 roots–>superior, middle, inferior trunks–>anterior and posterior divisions of each–> lateral, posterior and medial cords–> terminal branches: musculocutaneous, median, ulnar, radial, axillary

Question 5

The posterior cord of the brachial plexus is made up of

Answer 5

All 3 posterior divisions

Question 6

The lateral cord and medial cord are made up of

Answer 6

All anterior divisions
Lateral- anterior of the middle and superior trunks
Medial- anterior division of the inferior trunk

Question 7

The superior trunk is made up of

Answer 7

C5-6 roots

Question 8

The middle trunk is made up of

Answer 8

C7 root

Question 9

The inferior trunk is made up of

Answer 9

C8-T1 roots

Question 10

Levels of the terminal branches

Answer 10

Lateral cord: Musculocutaneous(C5-C7)and median nerve(C6-T1)
Posterior cord: axillary nerve (C5,C6) and radial nerve (C5-T1)
Medial cord: median nerve (C6-T1) and ulnar nerve (C8, T1)

Question 11

Proximal branches of the brachial plexus

Answer 11

Dorsal scapular nerve off of C5 root
Suprascapular off of superior trunk
Nerve to subclavius off of superior trunk
Long thoracic nerve off the inferior trunk
Medial pectoral nerve off medial cord
Medial cutaneous nerve of the arm (C8-T2) and medial cutaneous nerve of forearm (C8,T1) off of medial cord
Subscapular nerves (upper and lower) off of posterior cord
Thoracodorsal nerve off of posterior cord (between two subscapulars)
Lateral pectoral off of the lateral cord

Question 12

Musculocutaneous n- motor and cutaneous innervation

Pierces through:

Answer 12

Motor- anterior compartments of arm (flexors)
Cutaneous- skin of lateral forearm
Pierces the coracobrachialis m

Question 13

Axillary nerve- motor, cutaneous, clinically important landmark

Answer 13

Innervated the deltoid and teres minor m
Skin on the upper lateral arm
Travels near surgical neck of humerus with posterior circumflex humeral artery

Question 14

Radial nerve- motor, cutaneous, clinically important landmark

Answer 14

Innervates muscles in posterior compartment of the arm and forearm (extensors)
Skin on lateral and posterior arm, posterior forearm, dorsolateral hand
Travels in radial groove on posterior aspect of humerus with the deep brachial artery- midshaft fracture is relevant here

Question 15

In the forearm, the radial nerve splits into:

Answer 15

Superficial branch: sensory to dorsolateral hand
Deep branch: motor to most posterior compartment muscles of forearm. Changes name to posterior interosseous nerve once it pierces the supinator muscle and enters the posterior compartment

Question 16

Median nerve- motor, cutaneous, clinically important landmark

Answer 16

Innervates most muscles in anterior forearm (flexors) and some muscles in lateral hand
Skin on lateral palm and tips of digits 1-3
Travels through carpal tunnel

Question 17

Median nerve in the hand

Answer 17

Common/proper palmar digital innervate skin
Palmar cutaneous branch goes to skin at base of thumb/central palm: branches proximal to carpal tunnel and innervates the skin in central palm area
Recurrent branch innervates thenar muscles

Question 18

Which nerve in the hand may be spared from carpal tunnel compression?

Answer 18

Palmar cutaneous branch= exits prior to carpal tunnel compression

Question 19

Ulnar nerve- motor, cutaneous, clinically important landmark

Answer 19

Innervates 1.5 (FCU and medial half of FDP) muscles in anterior forearm and most intrinsic hand muscles
Skin on medial hand
Travels just posterior to the medial epicondyle of humerus- very superficially= numbness when laying on elbow for a very short time

Question 20

Ulnar nerve in the hand

Answer 20

Splits into several named branches that innervate most intrinsic hand muscles and the skin on medial part of hand and 1.5 digits

Question 21

Subscapular nerves- off of, spinal roots, innervates:

Answer 21

Off of the posterior cord
C5 (upper) C6 (lower)
Innervates the subscapularis and teres major m

Question 22

Thoracodorsal nerve

Answer 22

Off of the posterior cord
C6-C8
Innervates the latissimus dorsi- extend, adducts, and medially rotates the arm

Question 23

Pectoral nerves

Answer 23

Medial pectoral- off of medial cord, C8,T1, innervates the pectoralis major and minor m
Lateral pectoral- off of lateral cord, C5-C7, innervates pectoralis major m
Major: adducts, medially rotates the arm (also extend/flex arm)
Minor: stabilizes the scapula

Question 24

Dorsal scapular nerve

Answer 24

Off of root C5

Innervates rhomboid major and minor mm (retract scapula, depress glenoid cavity) and levator scapulae (elevates scapula)

Question 25

Long thoracic nerve

Damage*

Answer 25

Off of roots C5-C7
Innervates serratus anterior muscle (protracts scapula)
Damage to this nerve results in winged scapula

Question 26

Nerve to the subclavius

Answer 26

Off of superior trunk
C5,C6
Innervates the subclavius muscle (anchors clavicle)

Question 27

Suprascapular nerve

Answer 27

Off of superior trunk
C5,C6
Innervates the Supra spinatus (initiates abduction of arm) and infraspinatus m (laterally rotates the arm)

Question 28

Erb’s palsy

Answer 28

Superior trunk damage- musculocutaneous and axillary cutaneous nerve lost

Question 29

Klumpke’s palsy

Answer 29

Inferior trunk damage- radial, median and ulnar nerve damage