Topic 6 Flashcards
describe the formation of the brachial plexus
the brachial plexus is a complex plait of nerves formed by the joining of the ventral rami C5 to T1.
how does the brachial plexus divide
the brachial plexus divides into trunks, divisions, and cords.
what are the trunks of the brachial plexus
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.
what are the divisions of the brachial plexus
trunks divides into the anterior and posterior
how does the brachial plexus divide the divisions
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
what are the branches of nerves to the roots
dorsal scapular nerve - rhomboids
long thoracic nerve - serratus anterior
branches of nerves from the trunks
suprascapular nerve - supraspinatus and infraspinatus
nerve to subclavis - subclavis
branches of nerves from the cords
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
musculocutaneous nerve
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.
axillary nerve
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.
radial nerve
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.
median nerve
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.
ulnar nerve
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.
list the smaller branches of nerves from cords
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.
describe the distributions for the axillary and radial nerve
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.
describe the distributions for the musculocutaneous
root value = C567
motor - coracobrachialis, biceps, brachialis
sensory - skin of lateral forearm to base of thumb via a cutaneous nerve, elbow joint.
describe the distributions for the median nerve
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.
describe the distributions for the ulnar nerve
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.
radial nerve lesion
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.
ulnar nerve lesion
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.
median nerve lesion
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.
suprascapular nerve lesion
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.
long thoracic nerve lesion
motor loss - serratus anterior
functional motor loss - reduced scapulothoracic joint stability and implications on scapulothoracic rhythm.
deformity - winged-scapula
upper limb myotomes for shoulder
shoulder
abd and lateral rotation - C5
add and medial rotation - C6, C7, C8.
upper limb myotomes for elbow
flexion - C5, C6
extension - C7, C8.
upper limb myotomes for radioulnar joint
supination - C6
pronation - C7, C8.
upper limb myotomes for wrist joint
flexion and extension - C6 C7.
upper limb myotomes for digits
flexion and extension - C7, C8
ADD, ABD, opp - C8, T1.
