Brachial Plexus Lecture Notes

Overview

• The brachial plexus is a crucial structure in the upper limb.
• Generally starts at C5 and ends at T1.
  • May gain branches from C4.
  • No 8th cervical vertebra, but 8 pairs of cervical spinal nerves.

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Main Mnemonic: Mar mu

• M - Musculocutaneous
• A - Axillary
• R - Radial
• M - Median
• U - Ulnar

Key Points

• Understand the structure, branches, and muscle/cutaneous supply of the brachial plexus.

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Structure of the Brachial Plexus

Roots and Trunks

• C5 and C6 roots combine to form the upper trunk.
• C7 root forms its own trunk (middle trunk).
• C8 and T1 roots combine to form the lower trunk.

Trunks and Divisions

• Each trunk divides into an anterior and a posterior division:
  • Upper trunk: Anterior division, Posterior division
  • Middle trunk: Anterior division, Posterior division
  • Lower trunk: Anterior division, Posterior division

Cords

• Posterior cord: Formed by all posterior divisions.
  • Branches into Axillary and Radial nerves.
• Lateral cord: Formed by anterior divisions of upper and middle trunks.
  • Branches into Musculocutaneous nerve.
• Medial cord: Formed by anterior divisions of middle and lower trunks.
  • Branches into Ulnar nerve.
  • Median nerve formed by branches from both lateral and medial cords.

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Important Branches

Minor Branches

• Dorsal Scapular Nerve: Supplies rhomboids and levator scapulae.
• Long Thoracic Nerve: Supplies serratus anterior.
• Suprascapular Nerve: Supplies supraspinatus and infraspinatus.
• Nerve to Subclavius: Supplies subclavius muscle.

Lateral Cord Branches

• Lateral Pectoral Nerve: Supplies pectoralis major.

Posterior Cord Branches

• Upper Subscapular Nerve: Supplies subscapularis.
• Thoracodorsal Nerve: Supplies latissimus dorsi.
• Lower Subscapular Nerve: Supplies subscapularis and teres major.

Medial Cord Branches

• Medial Pectoral Nerve: Supplies pectoralis major and minor.
• Medial Brachial Cutaneous Nerve: Supplies skin of medial arm.
• Medial Antebrachial Cutaneous Nerve: Supplies skin of medial forearm.

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Major Nerves and Their Functions

Musculocutaneous Nerve

• Cutaneous Function: Supplies lateral forearm.
• Motor Function: Supplies coracobrachialis, brachialis, and biceps brachii.

Axillary Nerve

• Cutaneous Function: Supplies skin over the deltoid.
• Motor Function: Supplies deltoid and teres minor muscles.

Radial Nerve

• Cutaneous Function: Supplies posterior/lateral arm and dorsum of hand.
• Motor Function: Supplies triceps brachii, brachioradialis, and most forearm extensors.

Median Nerve

• Cutaneous Function: Supplies anterior surface of lateral hand and fingers 2 & 3.
• Motor Function: Supplies most flexor muscles of the forearm and some hand muscles.

Ulnar Nerve

• Cutaneous Function: Supplies the medial side of the hand, including the little finger.
• Motor Function: Supplies flexor carpi ulnaris and part of the flexor digitorum profundus, as well as all hypothenar muscles.

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Conclusion

• The brachial plexus intricately connects spinal nerves to upper limb muscles and skin.
• Understanding the structure and function is crucial for clinical practice.
• For further learning, check out related resources and platforms.