Lecture on Brachial Plexus

Overview

• The Brachial Plexus is a network of nerves that begins at the spinal cord, runs through the cervicothoracic region, and is crucial for the innervation of the upper limb.
• Originates from spinal cord segments C5 through T1 (sometimes C4).
• Composed of roots, trunks, divisions, cords, and branches.

Mnemonics

• Remember To Drink Cold Beer: Mnemonic for order of roots, trunks, divisions, cords, and branches.
• MARMU: Mnemonic for major nerves (Musculocutaneous, Axillary, Radial, Median, Ulnar).

Anatomy of Brachial Plexus

• Roots: C5, C6 roots form a trunk, C7 forms its own trunk, C8 and T1 form a trunk.
• Trunks:
  • Upper trunk (formed by C5, C6 roots)
  • Middle trunk (C7)
  • Lower trunk (C8, T1)
• Divisions:
  • Each trunk splits into an anterior and posterior division.
• Cords:
  • Posterior Cord: Formed by all posterior divisions. Braches to axillary,radial nerve
  • Lateral Cord: Formed by anterior divisions of upper and middle trunks.branched to musculocutaneous
  • Medial Cord: Formed by anterior division of the lower trunk.branches ulnar nerve
  • Medial and lateral cord :branches the median nerve

Branches and Nerves

• Musculocutaneous Nerve:
  • Origin: Lateral Cord
  • Motor Function: Innervation of anterior compartment of the arm (Coracobrachialis, Brachialis, Biceps brachii).
  • Cutaneous: Lateral forearm.
• Axillary Nerve:
  • Origin: Posterior Cord
  • Function: Innervation of Deltoid, Teres minor.
  • Cutaneous: Skin over lateral,posterior .(deltoid)
• Radial Nerve:
  • Origin: Posterior Cord
  • Function: Innervation of posterior arm(triceps,anconeus) and forearm muscles.(extensors:brochioradialis,ECR,Longus,Bravis,extensor digitorum,extensor indisis,extensor digiti minimi,ECU,Abbductor pollicus longus,EPL/B,supinator)
  • Cutaneous: Posterior and lateral surface of arm, dorsal hand., pollec
• Median Nerve:
  • Origin: Formed by branches of lateral and medial cords.
  • Function: Innervation of most forearm flexors(pronator teres,quadratus,palmaris longus, FCR, FD superficialis ,FDProfundus (radial part),some hand muscles.(lumbrecals 2,3 +thenar muscles)
  • Cutaneous: ventral ,Lateral palm and fingers.2,3 (ventral,dorsal)
• Ulnar Nerve:
  • Origin: Medial Cord
  • Function: Innervation of hypothenar muscles, some forearm flexors.(APB,Ulnar half of FDP,FCU)
  • Cutaneous: Medial hand.(ventral , dosal hand 1/3)

Minor Branches

• Dorsal Scapular Nerve (C5): Supplies Rhomboids and Levator Scapulae.
• Long Thoracic Nerve (C5-C7): Supplies Serratus Anterior.
• Suprascapular Nerve(upper trunk): Supplies Supraspinatus, Infraspinatus.
• Lateral Pectoral Nerve(lateral cord): Supplies Pectoralis Major.
• Upper Subscapular, Thoracodorsal(middle), Lower Subscapular Nerves(post cord): Supply various muscles like Subscapularis, Latissimus Dorsi, Teres Major.

• medial pectoral nerve,medial brachial cutaneous,medial anti brachial cutaneous (medial cord):supply pectoralis,post brachial region,anterior brachial region

Muscle Innervations

• Musculocutaneous Nerve: Flexion and supination of forearm.
• Axillary Nerve: Abduction, flexion, extension of shoulder.
• Radial Nerve: Extension of elbow, wrist, fingers.
• Median Nerve: Flexion of wrist and fingers, pronation of forearm.
• Ulnar Nerve: Flexion, abduction, and opposition of fingers.

Summary

• The brachial plexus is essential for motor and sensory innervation of the upper limb.
• Understanding the structure helps in diagnosing and managing nerve injuries.
• Mnemonics and diagrams are useful tools for learning the complex anatomy.