Session 5: The Brachial Plexus Flashcards
What are the 5 segments of the brachial plexus called?
Proximal to distal:
- roots
- trunks
- divisions
- cords
- terminal branches (peripheral nerves)
What are the names of the trunks of the brachial plexus? How many are there?
- 3
- superior, middle and inferior
Which nerve roots go into the brachial plexus?
- C5 (superior trunk)
- C6 (superior trunk)
- C7 (middle trunk)
- C8 (inferior trunk)
- T1 (inferior trunk)
Long thoracic nerve
- C5,6,7
- supplies serratus anterior
- Emerges from the root of the neck and runs over the surface of the serratus anterior muscle which it supplies.
supraclavicular and infraclavicular branches
x
Dorsal scapular nerve
- C5
- innervates rhomboids
Divisions
- anterior and posterior
- no terminal branches coming off diviisons
Trunks
- divisions recombine to form trunks
- upper 2 anterior divisions form lateral trunk
- all posterior fibers form the posterior trunk
- anterior trunk of inferior root forms median trunk
Summary of the motor nerves of the Upper limb (spinal levels)
- C3-7 supply shoulder girdle muscles
- C5-C6 supply shoulder joint muscles and elbow flexors
- C7-C8 supply elbow joint extensors
- C6-C8 supply wrist and coarse hand muscles
- C8-T1 supply small muscles of the hand (fine movements)
=> opposing movements are generally supplied by adjacent nerves -> see slide 13)
Dermatome vs. cutaneous nerve patterns
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.
Axillary nerve
- comes of the posterior branch of the brachial plexus
- passes posteriorly and then becomes lateral
- passes under the shoulder joint
- vulnerable to shoulder dislocation
- surgical neck of the humerus damage can also damage axillary nerve
- innervates deltoid muscle
What happens in axillary nerve damage?
- deltoid muscle wasting
- teres minor also supplied by that nerve
- superior lateral cutaneous nerve of arm -> loss of sensation in that area if that nerve is damaged
What does the axillary nerve innervate?
M:
- deltoid
- teres minor
S:
- name of the area
Radial nerve injury
- posterior muscle wasting if higher up
- wrist drop
- loss of power grip (you have to extend the wrist to get an efficient power grip)
=> depends on the level of the injury (where along the course of the nerve the damage occurs)
What is a plexus?
- nerve roots from different spinal levels merge together and produce peripheral nerves.
- these nerves usually have fibres from more than one spinal level
What are the names of the cords of the brachial plexus?
- lateral (anterior divisions of superior and middle trunk -> C5,6,7)
- posterior (made of all posterior divisions -> C5,6,7,8,T1)
- medial ( anterior division of inferior trunk -> C8,T1)
What are the names of the divisions of the brachial plexus?
- there are anterior and posterior divisions of each trunk (superior, middle, inferior)
What are the terminal branches of the brachial plexus called?
- musculocutanoues
What does the thoracodorsal nerve innervate?
Latissimus dorsi