Lecture Notes: The Brachial Plexus

Overview

• Discussion on the brachial plexus starting from C5 to T1 spinal nerves.
• Reminder to "Remember to Drink Cold Beer" for the brachial plexus components: Roots, Trunks, Divisions, Cords, and Branches (RTDCB).
• Mnemonic: Mar Mu (Musculocutaneous, Axillary, Radial, Median, Ulnar).

Structure of the Brachial Plexus

Roots

• C5 and C6: Form a trunk.
• C7: Forms its own trunk.
• C8 and T1: Form a trunk.

Trunks

• Upper Trunk: C5 and C6.
• Middle Trunk: C7.
• Lower Trunk: C8 and T1.

Divisions

• Each trunk splits into anterior and posterior divisions.
• Posterior divisions of all trunks join to form the Posterior Cord.

Cords

• Posterior Cord: Formed by posterior divisions; branches into axillary and radial nerves.
• Lateral Cord: Anterior divisions of the upper and middle trunks; forms musculocutaneous nerve.
• Medial Cord: Anterior division of the lower trunk; supplies ulnar nerve and contributes to the median nerve.

Branches of the Brachial Plexus

Major Nerves

• Musculocutaneous Nerve: Supplies coracobrachialis, biceps brachii, and brachialis.
• Axillary Nerve: Deltoid and teres minor muscles.
• Radial Nerve: Extensive supply including triceps brachii, anconeus, and extensors of the forearm.
• Median Nerve: Supplies pronator teres, flexor carpi radialis, palmaris longus, and more.
• Ulnar Nerve: Supplies flexor carpi ulnaris, ulnar half of flexor digitorum profundus, and hypothenar muscles.

Minor Branches

• Dorsal Scapular Nerve: Rhomboids and levator scapulae.
• Long Thoracic Nerve: Serratus anterior.
• Suprascapular Nerve: Supraspinatus and infraspinatus.
• Lateral Pectoral Nerve: Pectoralis major.
• Medial Pectoral Nerve: Pectoralis major and minor.
• Upper and Lower Subscapular Nerves: Subscapularis and teres major.
• Thoracodorsal Nerve: Latissimus dorsi.
• Medial Brachial Cutaneous and Medial Antebrachial Cutaneous Nerves: Skin sensation.

Function and Innervation

Cutaneous Innervation

• Musculocutaneous Nerve: Lateral forearm.
• Axillary Nerve: Posterior and lateral deltoid.
• Radial Nerve: Posterior and lateral upper limb, dorsum of hand.
• Median Nerve: Ventral and lateral palm, surfaces of digits 2 and 3.
• Ulnar Nerve: Ventral and dorsal medial one-third of hand.

Motor Innervation

• Musculocutaneous Nerve: Flexes elbow, supinates forearm.
• Axillary Nerve: Shoulder abduction, lateral rotation.
• Radial Nerve: Extends elbow, wrist, fingers; supinates forearm.
• Median Nerve: Pronation, wrist flexion, finger flexion.
• Ulnar Nerve: Wrist flexion, finger abduction/adduction, hypothenar movements.

Examination and Pathologies

• Mention of carpal tunnel syndrome related to median nerve.

Conclusion

• Key points about the brachial plexus, its structure, branches, and innervation.
• Encouragement to engage with additional resources and social media for further learning.