BRACHIAL PLEXUS
FORMATION :
It is formed by ventral primary rami of C5, C6, C7, C8 and T1.
COMPONENTS :
The brachial plexus consists of four components:
• Roots
• Trunks
• Divisions
• Cords
LOCATION :
• Roots and trunks lie in the root of neck.
• Divisions lie behind the clavicle.
• Cords lie in the axilla.
BRANCHES :
From Roots
• Dorsal scapular nerve (C5) for rhomboids.
• Nerve to serratus anterior (C5, C6 and C7) for serratus anterior as the name implies.
From Trunk (Only Upper Trunk Gives Branches)
• Suprascapular nerve (C5 and C6) for supraspinatus and infraspinatus muscles.
• Nerve to subclavius.
From Cords
• Lateral cord
Lateral pectoral nerve (C5-C7)
Lateral root of median nerve (C5-C7)
Musculocutaneous nerve (C5-C7)
Mnemonic: Laila Loved Majnu.
• Medial cord
Medial pectoral nerve for pectoralis major and pectoralis minor
Medial cutaneous nerve of arm
Medial cutaneous nerve of forearm
Medial root of median nerve
Ulnar nerve
Mnemonic: M4U
• Posterior cord
Upper subscapular nerve for subscapularis muscle
Lower subscapular nerve for subscapularis and teres major muscles
Nerve to latissimus dorsi (thoracodorsal nerve)
Axillary nerve for deltoid and teres minor muscles
Radial nerve
Mnemonic: ULNAR
APPLIED :
• Erb paralysis. It occurs due to injury of the upper trunk of brachial plexus at the Erb's point.
• Klumpke paralysis: It occurs due to injury of the lower trunk of brachial plexus.
• Horner syndrome: It occurs due to involvement of the sympathetic fibres (T1) • Winging of scapula: It occurs due to injury of the nerve to serratus anterior.
Erb Paralysis
Site of injury :
Erb's point (the region of upper trunk where six nerves meet, i.e. ventral rami of C5 and C6, anterior and posterior divisions of the upper trunk, and suprascapular nerve and nerve to subclavius)
Cause :
Undue (i.e. too much) separation of head from shoulder, e.g. (a) pulling of fetal head by forceps during delivery (birth injury) and (b) fall on shoulder.
Clinical features :
Arm hangs by the side. It is adducted and medially rotated, i.e. person is unable to abduct and laterally rotate the arm.
Forearm is extended and pronated, i.e. person is unable to flex and supinate the forearm.
Loss of sensations over a small area on the lower part of the deltoid.
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