Brachial Plexus

Nerve Plexuses All ventral rami except T2-T12 form interlacing nerve networks called plexuses found in the cervical, brachial, lumbar, and sacral regions Each resulting branch of a plexus contains fibers from several spinal nerves Each muscle receives a nerve supply from more than one spinal nerve Damage to one spinal segment cannot completely paralyze a muscle

Brachial Plexus

Formed by ventral rami of C5-C8 and T1 (C4 and T2 may also contribute to this plexus) It gives rise to the nerves that innervate the upper limb

Really Tired? Drink Coffee, Buddy! • Roots (ventral rami) • Trunks • Divisions • Cords • Branches

Roots Combine Forming Trunks Which Then Split Into Divisions C5 Anterior Division Upper Trunk C6 Posterior Division Anterior Division C7 Middle Trunk Posterior Division C8 Anterior Division Lower Trunk T1 Posterior Division

Divisions Form Cords • Anterior Upper • Posterior

Lateral Cord

• Anterior • Posterior Middle

Medial Cord

• Anterior • Posterior Lower

Posterior Cord

Cords Form Branches • Lateral Cord

Musculocutaneous n. Median n.

• Medial Cord

Ulnar n.

• Posterior Cord

Radial n. Axillary n.

The Brachial Plexus – Innervation of the Upper Limb • Axillary Nerve (Posterior Cord) – Runs posterior to the neck of the humerus – Deltoid and teres minor – Skin over inferior half of deltoid • Musculocutaneous Nerve (Terminal Branch of Lateral Cord) – Anterior arm – Innervates arm flexors – Distal to elbow, becomes cutaneous – sensation on lateral forearm

The Brachial Plexus – Innervation of the Upper Limb • Median Nerve (Lateral & Medial Cords) – Travels with brachial artery in arm, with radial artery in forearm – Muscles of flexor compartment of forearm except flexor carpi ulnaris and medial flexor digitorum profundus. – Through carpal tunnel to 5 intrinsic muscles of hand – Skin of lateral 2/3 of hand on palm side and dorsum of fingers 2 and 3

The Brachial Plexus – Innervation of the Upper Limb • Ulnar Nerve (Medial cord) – Descends along medial side of arm – Passes posterior to medial epicondyle = “” – Runs with ulnar artery in forearm – Innervates flexor carpi ulnaris and medial flexor digitorum profundus in forearm – Intrinsic muscles of hand except for 5 – Skin of medial 1/3 of hand anteriorly and posteriorly

The Brachial Plexus – Innervation of the Upper Limb • Radial Nerve (Posterior Cord) – Largest branch of brachial plexus – Humerus in radial groove supplying posterior compartment of arm – Curves anteriorly around lateral epicondyle, dividing into superficial and deep branch – Superficial branch to skin on dorsolateral surface of hand – Deep branch to extensor muscles of forearm

Superficial and Deep Muscles • • • • •

Flexor digitorum superficialis Flexor carpi radialis Pronator teres Palmeris longus Flexor carpi ulnaris

• Flexor pollicis longus • Flexor digitorum profundus • Pronator quadratus

Median n. Median n. Median n. Median n. Ulnar n. Median n. Median n. + Ulnar n. Median n.

Superficial Muscles • • • •

[Brachioradialis] Extensor carpi radialis longus & brevis Extensor digitorum Extensor carpi ulnaris

• • • •

Supinator Abductor pollicis longus Extensor pollicis longus & brevis Extensor indicis

Intrinsic Muscles of Hand • Thenar – Abductor pollicis brevis – Flexor pollicis brevis – Opponens pollicis – Adductor pollicis • Hypothenar – Abductor digiti minimi – Flexor digiti minimi brevis – Opponens digiti minimi

Median n. Median n. Median n. Ulnar n. Ulnar n. Ulnar n. Ulnar n.

Pg. 311

Intrinsic Muscles - Midpalmar • Lumbricals – Medial n. (lateral 2) – Ulnar n. (medial 2)

• Palmar interossei – Ulnar n.

• Dorsal interossei – Ulnar n.

Innervation of Muscles of Scapula • • • • • • • • • •

Lattisimus dorsi Thoracadorsal n. Subscapularis, teres major Subscapular n. Supraspinatus, infraspinatus Suprascapular n. Teres minor Axillary n. Deltoid Axillary n. Coracobrachialis Musculocutaneous n. Levator scapulae, rhomboids Dorsal scapular n. Pectoralis Minor Pectoral n. Serratus Ventralis Long thoracic n. Trapezius Accessory n.

Muscles – Origin on Scapula • Movement of arm – – – – – – – –

Subscapularis Supraspinatus Rotator Infraspinatus Cuff Teres minor Teres major Latissimus dorsi Corocobrachialis Deltoid

Pg. 296