Topic 6

Question 1

describe the formation of the brachial plexus

Answer 1

the brachial plexus is a complex plait of nerves formed by the joining of the ventral rami C5 to T1.

Question 2

how does the brachial plexus divide

Answer 2

the brachial plexus divides into trunks, divisions, and cords.

Question 3

what are the trunks of the brachial plexus

Answer 3

upper trunks - is formed when C5 and C6 unite.
middle trunk - is formed by only C7.
lower trunk - is formed by C8 and T1 uniting.

Question 4

what are the divisions of the brachial plexus

Answer 4

trunks divides into the anterior and posterior

Question 5

how does the brachial plexus divide the divisions

Answer 5

2 x anterior divisions from the anterior divisions form the lateral cord

all 3 posterior divisions form the posterior cord

1 anterior division of lower trunk forms the medial cord.

then these cords go into the nerves

Question 6

what are the branches of nerves to the roots

Answer 6

dorsal scapular nerve - rhomboids

long thoracic nerve - serratus anterior

Question 7

branches of nerves from the trunks

Answer 7

suprascapular nerve - supraspinatus and infraspinatus

nerve to subclavis - subclavis

Question 8

branches of nerves from the cords

Answer 8

upper scapula
lower scapula
thoracodorsal
medial cutaneous nerve of arm
medial cutaneous nerve of forearm
medial pectoral
lateral pectoral

the big five:
axillary nerve
radial nerve (and its posterior nerve)
musculocutaneous nerve
medial nerve (and its anterior branch)
ulnar nerve

Question 9

musculocutaneous nerve

Answer 9

from lateral cord, root value = C5-C7.
starts lateral to axillary artery , descends and pierces coracobrachialis, runs between biceps and brachialis.

branches - lateral cutaneous nerve of forearm
Vulnerability to injury - not very vulnerable but childbirth.

Question 10

axillary nerve

Answer 10

from posterior cord, rot value C5-C6.
starts posterior to axillary artery, divides deep into shoulder to supply shoulder joint, ant. branch winds around neck of humerus to supply deltoid and post. branch to supply deltoid and teres minor.

branches - superior/upper lateral cutaneous nerve of arm.

vulnerability to injury - shoulder dislocation.

Question 11

radial nerve

Answer 11

from posterior cord, root value = C5-T1

lies posterior to axillary nerve, ducks deep between lateral and medial heads of triceps brachii, travels in radial groove on humerus, enters ent arm between brachioradialis and brachialis, crosses elbow joint anteriorly and divides.

thicker than musculocutaneous and axillary nerve.

branches - deep branch/ posterior interosseous branch goes into supinator muscle then runs along posterior surface of interroseus membrane.

     - superficial branch radial only innervates skin and skin of joints. 

vulnerable to injury - fracture of humerus incorrect technique with crutches, can be entrapped between supinator muscle.

Question 12

median nerve

Answer 12

from lateral cord, root value = C5-C7 and medial cord, root value = C8 to T1.

the cords unite anteriorly, to axillary artery, travels deep to biceps brachii, deep to bicipital aponeurosis in cubital fossa, runs between heads of pronator teres, then deep to FDS, travels deep to flexor retinaculum to enter the hand-via the carpal tunnel.

branches - anterior interosseous branch is formed in cubital fossa, travels on anterior surface of interosseous membrane.

injury - deep cuts to forearm, superficial cuts at wrist, entrapment between heads of pronator teres, carpal tunnel syndrome.

Question 13

ulnar nerve

Answer 13

from medial cord, root value = C8-T1.

medial to axillary then brachial artery, travels anterior to triceps brachii, passes between medial epicondyle of humerus and olecranon, enters anterior forearm by passing through flexor carpi ulnaris heads, runs along FDP, lateral to ulnar atery enters hand by passing anterior to flexor retinaculum just lateral to the pisiform.

branches - none

injury - groove behind medial epicondyle, superficial cuts @ wrist, fall onto hand/compression in guyons canal.

Question 14

list the smaller branches of nerves from cords

Answer 14

lateral pectoral nerve (pec major), comes from lateral cord - can be missing.

• upper subscapular (subscapularis)
  thoracdorsal (latissimus dorsi)
• lower subscapular (lower subscap and teres minor).
• these are from posterior cord
• medial pectoral nerve (pectoralis minor and part of pec major of arm).
• medial cutaneous nerve of arm
• medial cutaneous nerve of forearm
• these are from medial cord.

Question 15

describe the distributions for the axillary and radial nerve

Answer 15

axiallary - root value = C56
- motor distribution: deltoid, and teres minor
- sensory distribution: skin over deltoid and shoulder joint

radial nerve - root value - C5678T1
- motor: all ulnarus extensors, brachioradialis, supinator, abd. pollucis.
- sensory: skin of posterior arm, forearm and hand (lateral 3.5 digits), wrist and elbow joints.

Question 16

describe the distributions for the musculocutaneous

Answer 16

root value = C567

motor - coracobrachialis, biceps, brachialis
sensory - skin of lateral forearm to base of thumb via a cutaneous nerve, elbow joint.

Question 17

describe the distributions for the median nerve

Answer 17

root value = C5678T1

FCR, PL, both pronators, FDS, FDP (lat), FPL, Abductor PB, FBP, opp poll, lateral 2 lumbricals.

skin of lateral 3.5 digits and corresponding palm and wrist and elbow.

Question 18

describe the distributions for the ulnar nerve

Answer 18

root value = C8T1

FCU, FDP (medial), PB, Abductor DM, opp DM, medial 2 lumbricals, adductor poll, all interossei.

skin of medial 1.5 digits and corresponding palm, wrist joint.

Question 19

radial nerve lesion

Answer 19

motor loss - triceps, anconeus, brachioradialis, supinator, ECRL, ECRB, ED, ECU, EI, abd PL.

sensory loss - posterior arm, forearm and hand (lateral 3.5 digits).

functional loss - no weightbearing on upper limb, cannot release grip

deformity - wrist drop.

Question 20

ulnar nerve lesion

Answer 20

motor loss - FCU, medial half FDP, hypothenar muscles, medial 2 lumbricals, adductor pol, all interossei.

sensory - palmer and dorsal skin of the medial one and a half digits and corresponding palm.

functional motor loss - loss of digital sweep (medial 2 digit), reduced power grip (unable to adduct thumb), sensory loss.

deformity - claw hand, wasting of hypothenar muscles occurs, medial 2 digits cannot extend.

Question 21

median nerve lesion

Answer 21

motor loss - FCR, FDS, FDL, lateral half FDP, both pronators. thenar muscles, lateral 2 lumbricals

sensory loss - palmer and dorsal skin of lateral 2.5 digits and corresponding palm.

functional motor loss - loss of digital sweep lateral 2 digits (loss of lumbricals), reduced precision grip (unable to position thumb), sensory loss (because median nerve delivers sensory info to brain for precision grip despite not being in conscious thought).

deformity - ape hand - wasting of thenar muscles and carpal tunnel syndrome.

Question 22

suprascapular nerve lesion

Answer 22

motor loss - supraspinatus and infraspinatus
sensory loss - shoulder joint
functional motor loss - reduced ability to seat humeral head and reduced range of shoulder motion, particularly ABD and ex rotation (inability to use all of glenoid surface).

deformity - maybe none noticeable at first, but during shoulder joint movement the humeral head slides forward.

Question 23

long thoracic nerve lesion

Answer 23

motor loss - serratus anterior
functional motor loss - reduced scapulothoracic joint stability and implications on scapulothoracic rhythm.

deformity - winged-scapula

Question 24

upper limb myotomes for shoulder

Answer 24

shoulder

abd and lateral rotation - C5
add and medial rotation - C6, C7, C8.

Question 25

upper limb myotomes for elbow

Answer 25

flexion - C5, C6
extension - C7, C8.

Question 26

upper limb myotomes for radioulnar joint

Answer 26

supination - C6
pronation - C7, C8.

Question 27

upper limb myotomes for wrist joint

Answer 27

flexion and extension - C6 C7.

Question 28

upper limb myotomes for digits

Answer 28

flexion and extension - C7, C8
ADD, ABD, opp - C8, T1.