Nerves of the Upper Limb Flashcards
What are the ventral rami that make up the brachial plexus?
C5,6,7,8 and T1
What is a prefixed brachial plexus?
A plexus from C4-8
What is a postfixed brachial plexus?
A plexus from C5-T2
What are the divisions of the brachial plexus?
roots, trunks, divisions, cords, branches
Which roots make up the upper trunk?
C5 and C6
Which roots make up the middle trunk?
C7
Which roots make up the lower trunk?
C8 and T1
What does each trunk divide into?
an anterior and posterior divisions
What do the anterior divisions supply?
flexor muscles and the skin overlying them
What do the posterior divisions supply?
extensor muscles and the skin overlying them
How are the cords named?
based on their relationship to the axillary artery - lateral, medial and posterior
What makes up the lateral cord?
anterior divisions of upper and middle trunks
What makes up the medial cord?
anterior division of the lower trunk
What makes up the posterior cord?
all of the posterior divisions
What makes up the musculocutaneous branch?
the lateral cord
What makes up the median nerve?
the lateral cord and the medial cord
What makes up the ulnar nerve?
the medial cord
What makes up the axillary nerve?
the posterior cord
What makes up the radial nerve?
the posterior cord
Where do the medial cutaneous nerves of arm and forearm branch off?
from the medial cord
Which parts of the brachial plexus are above the clavicle?
roots and trunks
Which parts of the brachial plexus are behind the clavicle?
divisions
Which parts of the brachial plexus are below the clavicle?
cords and branches
Which roots supply the musculocutaneous nerve?
C5,6,7
What muscles does the musculocutaneous nerve supply?
coracobrachialis, brachialis, biceps
Which muscle does musculocutaneous pierce?
coracobrachialis
Where does musculocutaneous descend?
in the arm above brachialis and deep to biceps
Where does musculocutaneous become superficial?
lateral to the tendon of biceps at the elbow joint - becomes lateral cutaneous nerve of forearm
Are injuries to musculocutaneous common?
no
What is the cutaneous supply of musculocutaneous?
lateral side of the forearm
Which roots supply the ulnar nerve?
C8 and T1 (with contribution from C7)
Where does the ulnar nerve descend in the arm?
medial to the artery
What injury at the elbow risks injury to the ulnar nerve?
fracture of the medial epicondyle
Where does the ulnar nerve descend in the forearm?
underneath FCU on top of the medial part of FDP
How does the ulnar nerve cross the wrist?
superficial to the flexor retinaculum - at risk in a laceration to the wrist
Which carpal bone does the ulnar nerve tuck in next to?
pisiform
What is the motor supply of the ulnar nerve?
FCU, medial half of FDP, and all of the muscles in the hand except the thenar eminence and half the lumbricals
What is the cutaneous supply of the ulnar nerve?
medial 1 and a half fingers and related dorsal and palmar aspect of the hand
What roots supply the median nerve?
C5,6,7,8,T1
How does the median nerve descend in the arm?
starts off anterior or lateral to the artery and as it descends it becomes medial to the artery
Where is the median nerve in the elbow?
medial to the artery
How does the median nerve descend in the forearm?
goes through the fibrous arch of FDS and then passes in the middle of the forearm between the superficial and deep muscles
How does the median nerve cross the wrist?
in the flexor retinaculum through the carpal tunnel - at risk in carpal tunnel syndrome
What is the motor supply of the median nerve?
all of the anterior muscles of the forearm except FCU and half of FDP and in the hand it supplies the thenar eminence and the lateral 2 lumbricals
What branch of the median nerve supplies the thenar eminence?
the recurrent thenar branch
What is the cutaneous supply of the median nerve?
lateral 3 and a half fingers and their associated palmar region at at least the nail beds of the lateral 3 and a half fingers for the dorsal aspect
Why isn’t the cutaneous supply affected in carpal tunnel syndrome?
because cutaneous branches are given off before it enters the carpal tunnel
What nerve roots supply the axillary nerve?
C5 and 6
Where does the axillary nerve enter the posterior compartment of the arm?
between teres major and teres minor
When is the axillary nerve at risk?
in a shoulder dislocation
What is the motor supply of the axillary nerve?
deltoid and teres minor
What is the cutaneous supply of the axillary nerve?
the military badge area
What nerve roots supply the radial nerve?
C5,6,7,8 and T1
Where does the radial nerve enter the posterior compartment of the arm?
beneath teres major
What is the path of the radial nerve in the arm?
spiral around the shaft of the humerus from medial to lateral
When is the radial nerve at risk?
in a fracture of the shaft of the humerus or a poorly fitted crutch
Where does the radial nerve travel in the forearm?
Divides into the posterior interosseus nerve (deep branch) and the superficial branch - the deep branch travels through supinator and then in the middle of the posterior compartment of the forearm and the superficial branch travels under brachioradialis - the deep branch supplies the muscles and the superficial branch is cutaneous
Where does the radial nerve cross the hand?
in the roof of the anatomical snuffbox on to the dorsum of the hand
What is the motor supply of the radial nerve?
all extensor muscles in the arm and forearm
Why doesn’t a fracture to the shaft of the humerus effect the action of the triceps?
because the branches to supply the triceps branch off just at the radial nerve emerges - well before it get to the humerus
What is the cutaneous supply of the radial nerve?
the posterior aspect of the arm, forearm and part of the dorsum of the hand - variable area but will always include the first webbed space
What is the cutaneous supply of the medial side of the arm?
the medial cutaneous nerve of arm and forearm
When do you see a dermatomal and myotomal deficit?
If the nerve damage is at the root not the nerve branches
What is the dermatomal supply of the middle finger?
C7
