Unit 3 Concept E Upper Limb Brachial Plexus

Concept Overview

  • Brachial Plexus of Nerves

    • Connects spinal cord to the upper limb

    • Comprised of nerves, functioning as highways for:

      • Efferent/Motor nerve fibers

      • Afferent/Sensory nerve fibers

Brachial Plexus: Definition & Outline

  • Definition:

    • A network of nerves carrying signals between the spinal cord and the upper limb.

  • Outline:

    • Illustrate all components of the Brachial Plexus

    • Name and describe specific nerves innervating the upper limb structures

Anatomy Background

  • Spinal Nerves:

    • Each spinal nerve (SN) branches into:

      • Anterior ramus (AR)

      • Posterior ramus (PR)

    • Multiple anterior rami form "plexuses" that innervate:

      • Upper Limb

      • Lower Limb

Overview of Brachial Plexus

  • Composition:

    • Comprised of roots, trunks, divisions, cords, and terminal branches

    • Responsible for innervation of upper limb structures

Named Segments of the Brachial Plexus

  • 5 Segments:

    • Roots: Anterior rami of C5-T1

    • Trunks: Formed from roots

    • Divisions: Each trunk splits into anterior and posterior divisions

    • Cords: Organized based on their position relative to the axillary artery

    • Terminal Branches: Named nerves emerging from the cords

Roots of the Brachial Plexus

  • Locations:

    • C5, C6, C7, C8, T1

  • Function:

    • Provide anterior rami that contribute to the brachial plexus

Trunks of Brachial Plexus

  • Three Trunks:

    • Superior Trunk: Communicates with C5 and C6 roots

    • Middle Trunk: Continuation of C7 root

    • Inferior Trunk: Communicates with C8 and T1 roots

Divisions of Brachial Plexus

  • Each Trunk has 2 Divisions:

    • Anterior Division: Supplies nerves for anterior compartments of the upper limb

    • Posterior Division: Supplies nerves for posterior compartments of the upper limb

Cords of the Brachial Plexus

  • Three Cords:

    • Posterior Cord: Receives posterior divisions of all three trunks

    • Lateral Cord: Receives anterior divisions of the superior and middle trunks

    • Medial Cord: Receives anterior division of the inferior trunk

Terminal Branches of Brachial Plexus

  • From Posterior Cord:

    • Axillary Nerve: Innervates deltoid and teres minor

    • Radial Nerve: Innervates all posterior arm and forearm muscles

  • From Lateral and Medial Cords:

    • Median Nerve: Supplies anterior forearm muscles (except certain flexors)

    • Musculocutaneous Nerve: Supplies anterior arm muscles

    • Ulnar Nerve: Supplies certain forearm muscles and hand muscles

Injuries and Presentations

  1. Axillary Nerve Injury:

    • Key Anatomy: Origin from posterior cord, passes behind surgical neck of humerus

    • Presentation: Difficulty abduction at shoulder

  2. Radial Nerve Injury:

    • Key Anatomy: Origin from posterior cord, runs posterior to humerus

    • Presentation: Loss of extension ("wrist drop")

  3. Musculocutaneous Nerve Injury:

    • Key Anatomy: Origin from lateral cord, pierces coracobrachialis

    • Presentation: Difficulty with elbow flexion and supination

  4. Median Nerve Injury:

    • Key Anatomy: Origin from lateral and medial cords, passes cubital fossa and carpal tunnel

    • Presentation: Weak hand grip and thumb opposition (Carpal Tunnel Syndrome)

  5. Ulnar Nerve Injury:

    • Key Anatomy: Origin from medial cord, runs posterior to medial epicondyle

    • Presentation: Complex hand deficits

Summary of Terminal Branches

  • 5 Terminal Branches:

    • Axillary Nerve: Innervates deltoid, teres minor

    • Radial Nerve: Innervates posterior arm & forearm muscles

    • Musculocutaneous Nerve: Innervates anterior arm muscles

    • Median Nerve: Innervates most anterior forearm muscles

    • Ulnar Nerve: Innervates specific forearm and hand muscles