Anatomy Limbs 5 - Brachial Plexus Flashcards
How does the brachial plexus divide as it moves distally?
Roots - Trunks - Divisions - Cords - Terminal branches
What muscle does the long thoracic nerve supply?
Serratus anterior
What muscle does the thorax-dorsal nerve supply?
Latissimus dorsi
Which spinal cord nerves make up the brachial plexus?
C5 - T1
Which nerve roots form the upper trunk?
C5 and C6
Which nerve roots form the middle trunk?
C7
Which nerve roots form the lower trunk?
C8 and T1
There is a lateral cord, posterior cord and medial cord. They are all named in relation to?
The axillary artery
Which nerve roots supply the shoulder girdle muscles?
c3-c7
Which nerve roots supply the shoulder joint muscles and elbow flexors?
C5-C6
Which nerve roots supply the elbow joint extensors?
C7-C8
Which nerve roots supply the wrist and coarse hand muscles
C6-C8
Which nerve roots supply small muscles of the hand (fine movements)
C8-T1
What are the terminal divisions of the posterior cord?
Axillary nerve and radial nerve
How is the axillary nerve commonly damaged?
Shoulder dislocation and fracturing the surgical neck of the humerus
Which 2 muscles does the axillary nerve innervate?
Deltoid and teres minor
How is axillary nerve damage assessed?
Test the superior lateral part of the shoulder/arm. Supplied by superior lateral cutaneous nerve of arm.
Area of anaesthesia if axillary nerve damaged
When and why is the radial nerve commonly damaged?
Radial nerve runs closely with the shaft of the humerus - so is susceptible in humeral fractures
What muscle of the arm does the radial nerve supply?
Triceps, and also muscles of the hand
How can radial nerve damage be assessed?
“Wrist drop” and anaesthesia of the dorsal hand
Radial nerve more proximally may also result in muscle masss wastage
ALSO LOSS OF POWER GRIP
Which cord is the musculocutaneous nerve derived from?
The lateral cord
Which muscles does the musculocutaneous nerve supply?
Anterior muscles of the arm
Why is the musculocutaneous nerve not often injured in trauma?
It is well protected by muscles
When might the musculocutaneous nerve be injured?
During surgery for breast cancer
From which cord is the ulnar nerve derived?
Medial cord
Which epicondyle does the ulnar nerve run behind?
Medial epicondyle
Which muscles does the ulnar nerve supply?
Flexor carpi ulnari and ulnar half of flexor digitorum profundus
Which muscles of the hand does the ulnar nerve supply?
Hypothenar muscles, lumbricals (4 and 5) and ALL dorsal/palmar interossei
When is the ulnar nerve commonly injured?
- Injury to medial epicondyle of humerus
2. Self harm - slashing wrists
How can you distinguish ulnar nerve injury in someone?
Claw-like appearance
Due to loss of lumbrical contraction - causes loss of flexion in metacarpal-phalangeal joints and weakened extension in the first interphalangeal joints
Which digits are largely spared in ulnar nerve damage?
Thumb, index finger and middle fnger
Why might ulnar injury at the wrist appear worse than ulnar injury at the elbow (counterintuitively)
at elbow, ulnar half of FDP also injured - meaning weaker flexion of interphalangeal joints = less claw like appearance than just at the wrist
Which cords form the median nerve?
Lateral and medial cords
What structure does the median nerve pass under en route to the hand
Flexor retinaculum
Which digits does the median nerve supply?
The thumb, index and middle fingers
What other region does the median nerve supply?
Proximal palmar regions
Wasting of the thenar eminence is a symptom of?
Carpal tunnel syndrome
Where is sensory anaesthesia present in carpal tunnel syndrome?
Thumb, much of the radial Half of the palm (but not the hypothenar region), index finger and much of middle finger
How come the long thoracic nerve is easily damaged?
It runs quite superficially to the serrates anterior muscle, so susceptible to trauma/stabbing etc
How can you tell damage to the long thoracic nerve?
Pressing against a wall = leads to winging of the scapula due to loss of activity from serratus anteior
Upper root injury (aka Erb-Duchenne palsy) can be caused by?
Falls which puts strain on the neck/ giving birth - can damage C5 and C6
Damage to the upper root can cause?
“Waiters tip”
Shoulder and anterior arm affected - forearm pronated due to lack of biceps supination
How can damage to the lower roots occur (C8/T1)
Overabduction due to gripping overhead to break a fall or in difficult births
Which cords can be affected by damage to the lower roots (C8/T1)
Medial cord and posterior cord
What is the outcome of lower root injury?
“Klumpke’s Palsy” - Klumpkes monkey falls from a tree
T1 - mainly supplies small muscles of hand via median and ulnar nerves - loss in activity gives clawed appearance
Clawed due to hyperextension of MCP joints and strong flexion of the fingers
