L7.1 - Nerves of UL Flashcards
In the brachial plexus, how are cords named?
According to their relation to the axillary artery
Pre-fixed brachial plexus?
Sometimes roots are higher (C4- 8)
Post-fixed brachial plexus?
Sometimes roots are lower (C6 - T2)
At which location are the following found:
a) Roots and trunks
b) Divisions
c) Cords and terminal branches
a) Roots and trunks - come from neck, supraclavicular
b) Divisions - behind clavicles, retroclavicular
c) Cords and terminal branches - infraclavicular
Msc Nerve - Path it descends into
1) Pierces coracobrachiallis
2) Descends deep to biceps but superior to brachialis
3) Finishes at the lateral side of the elbow before it becomes cutaneous lateral to tendon of biceps, aka lateral antebrachial cutaneous nerve
Injury to Msc nerve leads to?
Loss of motor innervation to arm and loss of cutaneous innervation of anterior lateral forearm (a bit of posterior lateral forearm as well)
Ulnar Nerve - Path it descends into
1) Medial side of axillary artery (becomes brachial artery at lower border of teres major)
2) Passes behind medial epicondyle
3) Slips through 2 heads of FCU and under it. Lies superior to FDP
4) Goes over Flexor Retinaculum and into hand (tucked in under pisiform bone)
Ulnar nerve - motor innervation?
Supplies all muscles of hand except what median nerve supplies:
- FCU
- FDP (medial half)
- Medial 2 lumbricals
- Hypothennar eminence
- Palmar and dorsal interossei
- Adductor Pol (the exception to the rule “all thenar muscles are supplied by the median nerve”)
- May or may not share thennar eminence with median nerve
Ulnar Paradox
The ulnar nerve is vulnerable at two location:
- Behind the medial epicondyle
- At the flexor retinaculum
If damaged distally (at flexor ret), the hand displays a claw-like appearance as the medial lumbricals (responsible for MCP flexion and IP extension) are weakened and instead display MCP extension and IP flexion.
If damaged proximally (near elbow), the ulnar (medial) 1/2 of FDP, the flexor digitorum profundus muscle may be denervated and flexion of the IP joints is weakened, reducing the claw-like appearance of the hand. (Instead, the fourth and fifth fingers are simply paralyzed in their fully extended position rather than flexed.)
This is called the “ulnar paradox” because one would normally expect a more proximal and thus debilitating injury to result in a more deformed appearance.
Cutaneous innervation of the hand - which nerves correspond to which regions?
Ulnar - Medial 1 1/2 digits
Median - Palmar 3 1/2 and nailbeds
Radial - Dorsal 3 1/2 minus nailbeds
What terminal nerve roots correspond to which nerves?
Ulnar - (C7) C8 T1 Msc - C5 - 7 Median - C5 - T1 Axillary - C5 - 6 Radial - C5 - T1
Median Nerve - motor innervation?
Supplies all forearm except FDP (medial half) and FCU
- Thennar muscles
- FDP (lat half)
- Lateral 2 lumbricals
Median Nerve - Path it descends into
1) Descends to forearm, either lateral or superficial to the artery
2) Crosses artery and goes medial to brachial artery when ulnar nerve goes behind medial epicondyle
3) Descends through cubittal fossa
4) Slips under fibrous arch of FDS
5) Descends to middle of forearm, FDS is superficial to it, FDP deep to it
6) Through carpal tunnel and into the hand (palm)
Median nerve - what splits before going through carpal tunnel?
The palmar branch of the median nerve which goes over the top of flexor retinaculum
Axillary nerve - Motor and sensory innervation
Deltoid and regiments patch, has a posterior branch that innervates teres minor a little bit
What space is the axillary nerve found in?
Quadrangular space - between long head of triceps, humerus, t min and maj
Axillary Nerve - Path it descends into
1) Goes beneath shoulder joint before going above T.maj - hence endangered in inferior dislocation of shoulder joint
2) Anterior branch goes around surgical neck of humerus from back to front, feeding branches to lateral part and anterior part of deltoid
Radial Nerve - Path it descends into
1) Goes through posterior wall of axilla to reach extensor compartment of arm and forearm
2) Exits below Teres Major
3) Goes in triangular interval between long and lateral head of biceps and Teres major
4) Spirals around back of humerus from medial to lateral in spiral groove
5) Piercing lateral intermuscular septum, exiting post compartment, going to ant compartment of arm
6) Tucks in under brachioradiallis
7) Splits into:
a) Sensory (superficial) which runs down lateral side of foream onto back of hand (lateral 3/1 digits on dorsum minus nail beds)
b) Motor (deep branch) pierces supinator and changes into posterior interosseous nerve after it goes through interosseous membrane
What 2 extensor muscles attach to supracondylar ridge above CEO?
ECRL and Brachioradialis
Interesting feature of radial nerve in regards to its branches?
Gives off branches early
