Lecture Notes: The Brachial Plexus

Introduction

• Brachial Plexus: A critical network of nerves.
• Lecture Structure:
  • Topography of nerves feeding into the brachial plexus.
  • Drawing a schematic of the brachial plexus.
  • Discussing supraclavicular and infraclavicular parts.
  • Ending with a quiz.

Topography of the Brachial Plexus

• Spinal Cord and Nerves:
  • Spinal nerve exits via intervertebral foramen.
  • Focus is on the anterior branch of spinal nerves.
• Nerves Forming the Brachial Plexus:
  • Spinal nerves C5, C6, C7, C8, and T1.
  • Sometimes C4 contributes.

Schematic of the Brachial Plexus

• Main Topographical Progression: Roots → Trunks → Divisions → Cords → Nerves.
• Mnemonic: “Really Tired, Drink Coffee Now”.
• Trunks Formation:
  • C5 & C6 form the superior trunk.
  • C7 forms the middle trunk.
  • C8 & T1 form the inferior trunk.
• Divisions:
  • Each trunk splits into anterior and posterior divisions.
• Cords:
  • Posterior divisions form the Posterior Cord.
  • Anterior divisions of upper and middle trunks form the Lateral Cord.
  • Anterior division of the inferior trunk forms the Medial Cord.

Main Nerves and Their Origins

• Musculocutaneous Nerve: Lateral cord.
• Ulnar Nerve: Medial cord.
• Radial and Axillary Nerves: Posterior cord.
• Median Nerve: Branches from lateral and medial cords.

Small Branches and Their Functions

• Dorsal Scapular Nerve (C5): Supplies rhomboid major/minor and levator scapula.
• Long Thoracic Nerve (C5, C6, C7): Supplies serratus anterior.
• Suprascapular Nerve: Supplies supraspinatus and infraspinatus.
• Subclavian Nerve: Supplies subclavius muscle.
• Lateral Pectoral Nerve: Comes from the lateral cord, supplies pectoralis major.
• Branches from Posterior Cord:
  • Upper Subscapular Nerve: Supplies subscapularis.
  • Lower Subscapular Nerve: Supplies subscapularis and teres major.
  • Thoracodorsal Nerve: Supplies latissimus dorsi.
• Branches from Medial Cord:
  • Medial Pectoral Nerve: Supplies pectoralis major and minor.
  • Medial Cutaneous Nerve of the Arm.
  • Medial Cutaneous Nerve of the Forearm.

Supraclavicular vs. Infraclavicular Parts

• Supraclavicular Part: Muscular branches from roots, trunks, and cords.
• Infraclavicular Part: Main nerves supplying the arm.

Infraclavicular Nerves and Their Innervations

• Musculocutaneous Nerve:
  • Cutaneous branch: Lateral forearm.
  • Motor branch: Coracobrachialis, brachialis, biceps brachii.
• Axillary Nerve:
  • Cutaneous branch: Deltoid skin.
  • Motor branch: Deltoid and teres minor.
• Radial Nerve:
  • Cutaneous branch: Posterior/lateral arm.
  • Motor branch: Triceps brachii, anconeus, and extensor muscles of forearm.
• Median Nerve:
  • Cutaneous branch: Palm surface and digits 2 & 3.
  • Motor branch: Anterior forearm muscles and thenar muscles.
• Ulnar Nerve:
  • Cutaneous branch: Medial hand.
  • Motor branch: Flexor carpi ulnaris, flexor digitorum profundus (4th & 5th digits), and intrinsic hand muscles.

Conclusion

• End of the lecture.
• Reminder to practice memorization through diagrams.
• Encouragement to engage with the video and support content creation.

These notes cover the entire scope of the brachial plexus lecture, aiding in understanding its structure, function, and associated nerves.