All Access Pass - 1 FREE Month!
Institutional email required, no credit card necessary.

Brachial Plexus

Brachial Plexus
Roots
  • Typically formed from the C5–T1 roots (their ventral rami).
Trunks
Divisions
Cords
  • Posterior cord forms the radial nerve and the axillary nerve.
  • Medial cord forms the ulnar nerve and a portion of the median nerve.
  • Lateral cord forms the musculocutaneous nerve, and branches from the lateral and medial cords join to form the median nerve.
Major Terminal Nerves
  • Radial nerve
    • Innervates extensor musculature.
  • Ulnar nerve
    • Innervates medial (pinky side of the hand) flexors that lie below the elbow.
  • Median nerve
    • Innervates lateral (thumb side of the hand) flexors that lie below the elbow.
Derived from the Roots
Relevant Anatomical Landmarks
Posteriorly
Medially (posteriorly)
  • Vertebral bodies of levels: C4, C5, C6, C7, and T1.
    • C5, C6, and C7 roots lie above their corresponding vertebrae T1.
    • C8 root lies below C7/above T1.
    • T1 root lies below its vertebra.
Laterally
Transverse
  • Clavicle
Axillary Artery
The axillary artery and its relationship to the brachial plexus
  • A continuation of the subclavian artery.
  • It climbs over the first rib, passes over the posterior cord, & beneath the lateral and medial cords.
  • The cords are named by their relationship to the axillary artery (specifically the 2nd portion of it):
    • Lateral cord lies lateral.
    • Posterior lies posterior.
    • Medial lies medial.