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Brachial plexus - anatomical depiction
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Brachial plexus - innervation pattern
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Brachial Plexus
Brachial Plexus
Roots
Typically formed from the C5–T1 roots (their ventral rami).
Trunks
Upper (superior) trunk
: C5, C6
Middle trunk
: C7
Lower (inferior) trunk
: C8, T1
Divisions
Posterior divisions
all join to form the posterior cord.
Anterior division
lower trunk forms the medial cord.
Anterior division
upper and middle trunks form the lateral cord.
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
Long thoracic nerve
Relevant Anatomical Landmarks
Posteriorly
Scapula
1st rib
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
Humerus
Coracobrachialis
muscle in the supero-medial shoulder
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.
Related Tutorials
Brachial Plexus - Essentials
Upper Extremity - Mononeuropathies & Plexopathies
Brachial Plexus - Advanced