Download Lecture 13 – The brachial plexus

Lecture 13 – The brachial plexus
Learning goals
The brachial plexus
 Describe the spinal cord segments that give rise to the brachial plexus
 Briefly describe the structure & function of the brachial plexus
 Describe the effects of muscle innervations of an upper of lower brachial plexus injury
Readings: CH4 – the shoulder girdle
Brachial Plexus
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Supplies the pectoral girdle & entire upper limb
Consists of a branching network of nerves
Derived from the anterior rami C5-T1 spinal nerves
most branches arise within the axilla
Organisation of the brachial plexus
Roots
 in the inferior part of
the neck, the roots
unite to form 3
trunks
Trunks
 superior, middle &
inferior
Divisions
 anterior & posterior
cords
 lateral, posterior &
medial
Trunks, divisions, cords in
relation to axillary artery
5 roots give rise to 3
trunks
superior
 union of C5 & C6
middle trunk
 continuation of C7 root
Interior trunk
 union of C8 & T1 roots
Lie in the posterior triangle of the neck (can palpate)
Each trunk divides into anterior & posterior divisions
Within the Axilla the divisions combine to produce 3 cords
Lateral cord
 superior & middle trunks of the anterior division unite to form the lateral cord
Medial cord
 anterior division of the inferior trunk continues as the medial cord
posterior cord
 all 3 trunks of the posterior division unit to form the posterior cord
Named according to their relationship with the axillary artery
Each cord ends at the lower border of the pectoralis minor
Each cord divides into terminal branches
Lateral cord
 Musculocutaneous nerve & lateral root of the median nerve
Medial cod
 Ulnar nerve & medial root of the median nerve
Posterior cord
 Axillary & radial nerves
Cords of the Brachial Plexus
Lateral cord
 Musculocutaneous nerve (C5 – C7)
o Innervates flexor muscles of the arm (specifically those on the ulnar/medial side e.g.
flexor digitorum superficialis & profundus)
 Median nerve, lateral root
Medial cord
 Ulnar nerve (C8-T1)
o Innervates flexor muscles of forearm (FCU, medial FDP), hypothenar eminence,
intrinsic hand muscles. Sensation medial hand
 Median nerve (C6-T1),, medial root
o Innervates forearm flexors, thenar eminence, 1st 2nd lumbricals. Sensation lateral
palm
Ulnar nerve damage
Indicated by:
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An inability to adduct or abduct the 4 fingers, but not the
thumb
o
Lumbricals & interossei
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Weakness in flexing & adducting the wrist
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Loss of sensation over the little finger
Also: pressure on elbow when in flexion
Median Nerve injuries
Indicated by:
 Numbness, tingling & pain in the palm & fingers
 Weak thumb movement s
 Inability to pronate the forearm
 Difficulty in proper wrist flexion