Innervation of the upper limb including peripheral nerves and spinal level innervation eg dermatomes

Question 1

spinal levels that contribute to the brachial plexus

Answer 1

C5-C8,T1

Answer 2

Roots
* Ventral rami of C5-C8,T1 spinal nerves

Trunks
* Superior trunk (C5 & C6)
* Middle trunk (C7)
* Inferior trunk (C8 & T1)

Divisions
* Anterior divisions
* Posterior divisions

Cords (named according to their relation to the axillary artery)
* Lateral cord
* Medial cord
* Posterior cord

Branches

Question 3

Name the 5 terminal branches of the brachial plexus. Next to each, list the spinal cords and levels that contribute to each nerve.

Answer 3

Musculocutaneous nerve – lateral cord (C5-7)
Median nerve – (C5-8, T1) and formed by the union of the:
Medial root from the medial cord (C5-C7)
Lateral root from the lateral cord (C8-T1)
Ulnar nerve – medial cord (C7, C8, T1)
Axillary nerve – posterior cord (C5-6)
Radial nerve – posterior cord (C5-C8, T1)

Question 4

Dermatome definition:

Answer 4

an area of skin supplied by a single spinal nerve

Question 5

Cutaneous nerve supply definition

Answer 5

an area of skin supplied by a single peripheral nerve

Question 6

myotome definition

Answer 6

a group of muscles innervated by a single spinal nerve

Question 7

Summary of myotomes for the upper limb

Answer 7

C4 -Shoulder elevation
C5- Shoulder (glenohumeral) abduction
C6-Elbow flexion or wrist extension
C7-Elbow extension
C8-Finger flexion
T1-Finger abduction & adduction

Question 8

Summary of dermatomes for the upper limb

Answer 8

C5 Lateral upper arm (deltoid area)
C6 Lateral forearm, thumb
C7 Middle finger
C8 Medial forearm, little finger
T1 Medial upper arm (near axilla)