Overview of the Brachial Plexus

Introduction

• Lecturer: Dr. Morton, noted anatomist
• Topic: Brachial Plexus
• Focus: Understanding its roots, trunks, divisions, cords, and branches

Brachial Plexus Basics

• Location: C5 to T1 spinal cord levels
• Function: Provides motor and sensory innervation to the upper limb

Components

• Roots: C5, C6, C7, C8, T1 (ventral rami)
• Trunks: Upper, Middle, Lower
• Divisions: Anterior and Posterior
• Cords: Lateral, Medial, Posterior
• Branches/Terminal Branches: Axillary, Radial, Musculocutaneous, Median, Ulnar

Mnemonic

• "Randy Travis Drinks Cold Beer" for Roots, Trunks, Divisions, Cords, Branches

Details on Components

Roots

• Position: C5 to C8 roots above respective vertebrae; C8 below C7, above T1
• Associated Structures:
  • Dorsal Scapular Nerve: Innervates levator scapulae, rhomboid muscles
  • Long Thoracic Nerve: Innervates serratus anterior (mnemonic: "Roses are red...")
• Sensory and Motor Functions:
  • Each root has a dermatome (area of skin) and myotome (movement)
  • C5: Shoulder abduction, C6: Elbow flexion, C7: Elbow extension, C8: Finger flexion, T1: Finger abduction

Trunks

• Formation:
  • Upper: C5-C6
  • Middle: C7
  • Lower: C8-T1
• Nerves:
  • Suprascapular Nerve: Innervates supraspinatus, infraspinatus

Divisions

• Purpose: Distinguish ventral (flexors) and dorsal (extensors) muscle masses
• Anatomy: No specific branches

Cords

• Relation to Axillary Artery: Lateral, Medial, Posterior
• Branches:
  • Lateral Cord: Lateral pectoral nerve (innervates pectoralis major)
  • Medial Cord:
    • Medial pectoral nerve (innervates pectoralis major and minor)
    • Medial cutaneous nerves of arm and forearm
  • Posterior Cord:
    • Upper and lower subscapular nerves (innervate subscapularis)
    • Thoracodorsal nerve (innervates latissimus dorsi)

Terminal Branches

Axillary Nerve

• Innervates: Deltoid, teres minor
• Cutaneous Nerve: Lateral cutaneous nerve of the arm

Radial Nerve

• Innervates: Triceps, forearm extensor muscles
• Sensory Branch: Dorsal hand

Musculocutaneous Nerve

• Innervates: Biceps, brachialis, coracobrachialis
• Cutaneous Nerve: Lateral cutaneous nerve of the forearm

Median Nerve

• Innervates: Forearm flexors, thenar muscles
• Sensory Branch: Palmar surface of thumb, index, and middle fingers

Ulnar Nerve

• Innervates: Flexor carpi ulnaris, intrinsic hand muscles
• Sensory Branch: Medial half of the hand

Conclusion

• Summary: Detailed anatomy of the brachial plexus with emphasis on roots, trunks, divisions, cords, and terminal branches
• Clinical Reference: Useful for identifying specific nerve function and related muscles