Nerves and vessels of the upper limb Flashcards
State the sections of the brachial plexus
ROOTS (from anterior rami) TRUNKS DIVISIONS CORDS (TERMINAL) BRANCHES (peripheral nerves)
Read That Damn Cadaver Book!
T/f the roots of the brachial plexus refers to the anterior and posterior roots emerging from the spinal cord
F!
Anterior/posterior roots from spinal cord firstly combine to form spinal nerve. There are then anterior and posterior rami which contain mixed motor/sensory function.
The roots of the brachial plexus are separate from these spinal cord roots, and are formed by anterior rami
What are the roots of the brachial plexus
C5-T1 from anterior rami
Which nerve(s) emerge(s) from the root.
Dorsal scapular nerve (C5)
Long thoracic nerve (C5-C7)
Where do the roots exit to get into the base of the neck
These nerves pass between the anterior and medial scalene muscles to enter the base of the neck.
What does the dorsal scapular nerve do
levator scapulae (as does cervical nerve (C3,C4), rhomboid major, and rhomboid minor muscles.
What are the names of the trunks? Which innervation do each contain
Superior (C5,C6)
Middle (C7)
Inferior (C8, T1)
Which nerve(s) emerge(s) from the trunks. What does it/they do
The subclavian nerve (C5, C6) from the superior trunk.
Innervates the subclavius muscle
What are the names of the divisions and how many are there
There are anterior and posterior divisions of each trunk, so 6 divisions
NOTE it is A, P, A, P, P, A
Which nerve(s) arise(s) from the divisions
Suprascapular nerve (C5, C6), from the anterior division of the superior trunk
What are the names of the cords, how many are there, and what are their contributions
Lateral (AS, AM)
Posterior (SP, MP, IP)
Medial (AI)
Which nerve(s) emerge(s) from the cords
Lateral: lateral pectoral nerve (C5-C7)
Posterior: Upper subscapular nerve (C5, C6), lower subscapular nerve (C5, C6) and thoracodorsal nerve (C6-C8)
Medial: medial pectoral nerve (C8, T1), medial cutaneous nerve of the arm, medial cutaenous nerve of the forearm
What is the function of the lateral pectoral nerve
Innervates pectoralis major (along with the medial pectoral nerve)
What is the function of the upper subscapular nerve
Innervates subscapularis
What is the funtion of the lower subscapular nerve
Innervates subscapularis, and TERES MAJOR
What is the function of the thoracodorsal nerve
Innervates lat. dorsi
What is the function of the medial pectoral nerve
Innervates pectoralis major
Innervates pectoralis minor
What are the terminal branches of the brachial plexus?
Musculocutaneous (from lateral cord), C5-C7
Axillary (posterior cord)- C5,6
Radial (posterior cord)- C5-T1
Median nerve (lateral root of median nerve from lateral cord=C6,7, medial root from medial cord=C8,T1).
Ulnar (medial cord)- C8,T1, C7
(my auntie ripped my uncle)
What are the CORDS named according to
according to their relationship to the axillary artery.
The posterior cord is posterior to the artery etc.
Which spinal cord segments supply the shoulder girld muscles
C3-C7
Which spinal cord segments supply the shoulder joint muscles and elbow flexors
C5-C6
Which spinal cord segments supply the elbow joint extensors
C7,C8
Which spinal cord segments supply the wrist and coarse hand muscles
C6-C8
Which spinal cord segments supply the small muscles of hand
C8-T1
Which spinal cord segments abduct the arm from when it is perpendicular to body
C5
Which spinal cord segments adduct the arm from when it is perpendicular to body
C6,7,(8)
Which spinal cord segments flex the elbow
C5,6
Which spinal cord segments extend the elbow
C7,8
Which spinal cord segments pronate
C7,8
Which spinal cord supinate
C6
Which spinal cord segments flex the wrist
C6, 7
Which spinal cord segments extend the wrist
C6,7
Which spinal cord segments abduct the fingers
T1
Which spinal cord segments extend the finger
C7,8
Which spinal cord segments flex the finger
C7,8
LEARN THE DERMATOMES
…
T/F the dermatome and cutaneous nerve patterns are similar
F: Because of all the fibre recombination that takes place in a plexus, the pattern of cutaneous nerve distribution is very different from the dermatome pattern
WHY
Where does the axillary nerve come form
Posterior cord
How is the axillary nerve damaged
Commonly damaged through dislocations of shoulder and fracture of the surgical neck of the humerus.
Which muscles are supplied by the axillary nerve
Deltoid, teres minor, and glenohumeral
What is the course of the axillary nerve
Exits axillary fossa posteriorly, passes through quadrangular space with posterior circumflex humeral artery, gives rise to superior lateral brachial cutaneous nerve, then winds around surgical neck of humerus deep to deltoid
What would happen if axillary nerve was damaged
Wasting of deltoid/analgesia in a spot on the lateral arm due to lack of superior lateral cutaenous nerve of the arm
Where is the radial nerve derived from
Posterior cord
Outline the course of the radial nerve
Exits axillary fossa POSTERIOR to axillary artery
Passes posterior to humerus in the radial groove with the deep brachial artery between lateral and medial heads of triceps
Perforates lateral intermusclar septum
Enters cubital fossa
Rivides into superfical (cutaneous) and deep (motor) radial nerves
How can the radial nerve be damaged
The radial nerve runs closely apposed to the shaft of the humerus, so can be damaged in humeral fractures.
What can happen in radial nerve damage
Wrist drop and anaesthesia of the dorsal hand
(around the thumb area)
Loss of muscle mass evident in the arm and forearm.
Remember what the guy said in dissection: the radial nerve gives off its branches very high, so the triceps us
What loss of function occurs in radial nerve damage
Loss of power grip
wrist extension required
Where is the musculocutaneous nerve derived from
The lateral cord
Outline the course of the musculocutaneous nerve
Pierces coracobrachialis to exit the axilla.
Descneds between biscpes brachii and brachialis. Supplies both.
Continues as lateral cutaneous nerve of the forearm
When is musculocutaenous nerve injured
not often injured in trauma as it is well protected by musclesMay be damaged during surgery for breast cancer
Where is the ulnar nerve derived from
Medial cord
Outline the course of the ulnar nerve
Descends medial arm, passes posterior to medial epicondyle of hmerus
Descends ulnar aspect of forearm to hand
Function of ulnar nerve
FCU, ulnar half of flexro digitorum produndus, most intrinsic muscles of hand, skin of hand medial to axial line of digit 4
Common sites of ulnar nerve injury
Medial epicondyle, near the ulnar stylus
Injuries to medial epicondyle of humerus cause injury to the ulnar nerve at the elbow.
When might clinicians see ulnar nerve damage in the wrist
Self harm/assisted suicide
What happens in ulnar nerve injury
Claw deformity
What cuases claw deformity in ulnar nerve injudry
lumbrical contraction means loss of flexion of the MPJs and weakened extension of the IPJs.
THEREFORE YOU GET AN EXTENED MPJ and a flexed IPJ
What other motor deficits will be evident: in ulnar nerve damage
aside from claw like:
Many small muscles of hand affected but thumb, index and middle finger movements largely spared
Adductin and abduction due to interossei muscles
Sensory deficits in ulnar nerve
skin of hand medial to axial line of digit 4
When is claw deformity worse in ulna nerve damage, near the wrist or the elbow and why
AT WRIST WORST THAN ELBOW (paradox as you expect to be worse when more proximal)
This is because the ulnar nerve also innervates the ulnar half of FDP, flexion of the IP joints is weakened (there is flexion at IPJ because of loss of the extension usually provided by the lumbicals, but having less flexion from FDP as would occur when the elbow is involved not the wrist reduces the flexion ), therefore less claw-like appearance
Where does the medial nerve come from
Medial and Lateral Cords
What is the path o the median nerve
Lateral and medial roots (frm the cords) merge to form median nerve lateral to axillary artery
Descends throiguh arm adjacent to brachial artery, nerve crosses anterior to artery to lie medial to artery in the cubital fossa
Runs through the carpal tunnel
Where does the median nerve run within the carpal tunnel
Quite laterally
T/F ulnar nerve lies LATERAL to the median nerve in the carpal tunnel
F! The ulnar nerve doesn’t run within the carpal tunnel!!!
When is the median nerve most commonly entrapt
Carpal tunnel syndrome
Signs in carpal tunnel syndrome
Wasting of thenar eminence (adductor pollicis may become prominent as it is NOT supplied by the median nerve)
Sensory deficit lateral to the axial line of the ring finger palmar sid
T/F sensory damage in ulnar nerve damage is more signfiicant than in median nerve damage
F…. inconvenient in ulnar nerve but severely debitilating in mdian nerve damage
What does the long thoracic nerve innervate
Serratus anterior muscle
Where does the long thoacic nerve lie
is relatively superficial, therefore easily damaged
What will damage to long thorac nerve resutlt in
Pressing against a wall will lead to “winging” of the scapula resulting from the loss of activity of serratus anterior.
Injuries to the upper roots of the brachial plexus is ferred to as what
Erb-Duchenne Palsy (C5,C6)
When can erb dchenne palsy occur
During injury (see the image) or during birth
What occurs in erb’s palsy to limb position and why
“Waiter’s Tip” Position with Upper Root Injury
Many muscles affected (shoulder, anterior arm). Forearm pronated by lack of biceps supination.
What is injury to the lower roots called
Klumpke’s Palsy
What is the common cause of klumpke’s palsy
Common cause is over-abduction due to gripping overhead to break a fall.
T1 (and sometimes C8)
or during birth
What occurs in lower root injury
T1 mainly supplies the small muscles of the hand via the ulnar and median nerves. Loss of their activity results in clawed hand.
Why does the claw occur in klumpke’s palsy?
/…
What does ulnar nerve supply in the arm
Nothing
The ulnar nerve supplies flexor digitorum profundus to which digits
medial, so 4 and 5
What can klumke’s result from
Klumpke’s monkeys fall from the tree (over abduction)
