12.6 Innervation of the Upper Limb Flashcards
Which spinal levels comprise the brachial plexus?
C5-T1
Dorsal scapular nerve root(s)
C5 (Imagine a handprint on the rhomboids; five fingers)
Long thoracic nerve root(s)
C5-C7 (1,3,5,7,9; remove the three — SA runs from ribs 1-9, nerve roots are C5-C7)
Subclavius nerve root(s)
C5-C6 (Six-five-ius)
Which roots make up which trunks of the brachial plexus?
Superior trunk: C5-C6
Middle trunk: C7
Inferior trunk: C8-T1
Which division of the brachial trunks that arise from the cervical spine correspond to flexors vs extensors?
Anterior division: flexors
Posterior division: extensors
Suprascapular nerve root
C5-C6 (above scapula, and below clavicle [six-five-ius])
Which divisions of which roots of the brachial plexus contribute to which cords? Around which blood vessel do the cords wrap?
- Anterior divisions of sup. and middle root create lateral cord
- Anterior division of inf. root creates medial cord
- Posterior divisions of all three create posterior cord (this one’s easy)
Which nerves arise from the lateral cord of the brachial plexus?
- Lateral pectoral nerve
- Lateral root of median nerve
- Musculocutaneous
(Rugby mnemonic; “long legged movers”)
Which nerves arise from the medial cord of the brachial plexus?
- Medial pectoral nerve
- Medial brachial cutaneous
- Medial antebrachial cutaneous
- Ulnar
- Medial root of medial nerve
(Rugby mnemonic; “make many moves using muscles”)
Which nerves arise from the posterior cord of the brachial plexus?
- Upper subscapular
- Lower subscapular
- Thoracodorsal
- Radial
- Axillary
(Rugby mnemonic; “ULTRA competitive”)
Which nerve innervates most forearm flexors?
Median nerve
Which nerve innervates most intrinsic hand muscles?
Ulnar nerve
Which nerve innervates all the extensors of arm, forearm, posterior skin of arm, forearm, and hand (but not fingers)?
Radial nerve
Which are the three “interesting” nerves of the supraclavicular branches of the brachial plexus? Why?
- Dorsal scapular (rhomboids, levator scapulae, traps)
- Long thoracic (serratus anterior)
- Suprascapular (supra and infraspinatus)
Is the long thoracic nerve deep or superficial to serratus anterior? Why is this important? Which muscle does this nerve pierce?
- Superficial to
- This makes it vulnerable to damage :(
- Pierces middle scalene
Describe the course of the suprascapular artery and nerve relative to the AC ligament
Nerve: under
Artery: above
Therefore, nerve can get impinged
Which area of the forearm skin does the musculocutaneous nerve innervate?
Lateral
From which two cords of the brachial plexus does the median nerve arise? Which artery is this in front of?
Medial and lateral cords, in front of the axillary artery.
Which nerve gives rise to the anterior interosseus nerve? What muscles does it innervate?
- Median nerve
- Innervates radial part of flexor digitorum profundis, flexor pollicis longus and pronator quadratus
Which nerves innervate the thenar/hypothenar muscles?
Thenar: median
Hypothenar: ulnar
Describe cutaneous innervation of the hand
Ulnar: medial 1.5 digits (on ulnar side)
Median: anterior of other digits + posterior distal phalanges of these
Radial: Lateral base of thumb and posterior aspect of 3.5 digits (except those fingertips)
True or false: the whole median nerve passes through the carpal tunnel.
- False
- The palmar branch of the median nerve runs superficial to the flexor retinaculum
(Note: the ulnar nerve also has a palmar branch)
What structures travel through the carpal tunnel?
- Median nerve
- Tendons of flexor digitorum profundus (4x)
- Tendons of flexor digitorum superficialis (4x)
- Tendon of flexor pollicis longus
What does the ulnar nerve innervate?
- Flexor carpi ulnaris
- Medial half of FDP
- Intrinsic muscles of hand (other than thenar muscles and two lateral lumbricals)
Describe the passage of the ulnar nerve across the elbow joint
Runs on the extensor (i.e., posterior) side of the elbow, in the ulnar groove of the medial epicondyle.
(This is why medial epicondyle fractures can cause damage to the ulnar nerve)
The ulnar nerve enters the hand through the ______ canal, along with the ulnar artery and ulnar vein, which is between the _____ and _____ bones.
Guyon’s canal. Between pisiform and hamate bones.
What muscles does the radial nerve innervate/not innervate?
- Upper arm: triceps
- ALL posterior compartment forearm muscles
- NO intrinsic hand muscles
The median/ulnar/radial nerves travel through the two heads of which respective muscles?
Median: pronator teres
Ulnar: flexor carpi ulnaris
Radial: supinator
Which major arteries do which of the median/ulnar/radial nerves travel with?
Median/Ulnar: Brachial artery
Radial: Profunda brachii
Where does the superficial branch of the radial nerve run? What muscles does it innervate?
- Runs with radial artery under brachioradialis
- Superficial branch supplies brachioradialis, anconeus, and extensor carpi radialis longus
The deep branch of the radial nerve becomes the ______. The counterpart to this nerve originates from the ____, and is called _____.
- Becomes the posterior interosseus nerve
- Counterpart is anterior interosseus nerve, which originates from median nerve
Which muscles does the axillary nerve innervate? What are its roots?
- Deltoid
- Teres minor
Roots: C5-C6
Which nerve innervates subscapularis and teres major? What are its roots?
- Subscapular nerve
Roots: C5-C6
Describe the sensory innervation of the arm (not hand)
Lateral shoulder: axillary
Distal arm and posterior arm/forearm: radial
Lateral forearm: musculocutaneous
