Axilla and Brachial Plexus Flashcards
Important structures in the axilla:
- Axillary artery
- Axillary vein(s)
- Axillary lymph nodes
- Brachial plexus of nerves
- Pectoralis minor muscle
- Biceps brachii muscle
- Coracobrachialis muscle
- Axillary tail of female breast.
Axilla “Armpit”
- Floor: axillary fascia and skin of armpit
- Apex: passageway for structures entering or leaving the shoulder and arm; bounded by 1 rib, clavicle and superior portion of scapula.
- Anterior wall: pectoralis major & minor muscles, clavipectoral fascia
- Posterior wall: Subscapularis, teres major, latissimus dorsi, long head of triceps brachii muscle.
- Medial wall: superior rib cage, intercostal and serratus anterior muscles.
- Lateral wall: humerus.
Arterial supply of axilla
Brachiocephalic trunk -> subclavian artery -> axillary artery -> brachial artery -> radial/ulnar arteries
Venous drainage of axilla
Superficial: cephalic & basilic veins
Dive down to axillary vein
Brachial veins surround brachial artery
-> Axillary v. -> subclavian v.
Axillary lymph nodes
20-30 nodes divided into five groups: • Central nodes • Lateral (brachial, humeral) nodes • Posterior (subscapular) nodes • Anterior (pectoral) nodes • Apical (subclavian) nodes
Brachial plexus
Neurovascular bundle in axilla= • Axillary artery • Axillary vein • Cords of brachial plexus => all bound in the axillary sheath • Brachial plexus = ventral rami of spinal nerves C5-T1.
Posterior triangle of neck
Middle scalene and trapezius
Anterior scalene
Sternocleidomastoid
Functions of nerves in the upper limb
- Motor innervation to muscles
- Sensory innervation to skin & deep structures
- Vascular tone by sympathetic vasomotor nerve fibres
- Secretomotor fibres to supply sweat glands
Brachial plexus
- 5 roots (ventral rami)
- 3 trunks
- 6 divisions (3 anterior, 3 posterior)
- 3 cords (named for their relationship to the axillary artery)
- 5 large terminal branches (M, A, R, M, U)
Named nerves of the Brachial Plexus
Anterior rami of C5-T1
Supplies: Muscles of shoulder (superficial back muscles, anterior thoracic wall muscles)
All muscles of upper extremity.
Upper limb skin.
Posterior cord nerves
- Derived from posterior divisions of all 3 trunks.
- (ULTRA)
- Upper subscapular nerve
- Lower subscapular nerve
- Thoracodorsal nerve
- Radial nerve
- Axillary nerve
Lateral cord nerves
- Derived from the anterior divisions of the superior and middle trunks.
- (LML)
- Lateral pectoral nerve
- Musculocutaneous nerve
- Lateral root of median nerve
Medial cord nerves
- Derived from the anterior division of the inferior trunk.
- (M4U)
- Medial pectoral nerve
- Medial cutaneous nerve of arm
- Medial cutaneous nerve of forearm
- Medial root of the median nerve
- Ulnar nerve
Brachial Plexus: Terminal Nerves
- Axillary —innervates the deltoid, teres minor, and skin and joint capsule of the shoulder
- Musculocutaneous —innervates the anterior arm muscles and skin of lateral forearm
- Median —innervates the skin, most flexors and pronators in the forearm, and thenar muscles
- Ulnar —supplies the flexor carpi ulnaris, medial half of flexor digitorum profundus, most intrinsic muscles of the hand, and skin of medial aspect of hand
- Radial —innervates essentially all extensor muscles, supinators, and posterior skin of limb
Axillary nerve (C5-C6)
Deltoid muscle
Teres minor muscle
Derived from posterior cord and passes posterior to humerus wrapping transversely across lateral aspect of humerus
Musculocutaneous nerve (C5-C6-C7)
Coracobrachialis muscle
Brachialis muscle
Biceps brachii muscle
Derived from medial cord, pierces through
coracobrachialis, travels deep to biceps brachii / superficial to brachialis then passes
superficially to dermis to innervate lateral skin
on forearm
Median nerve (C5-C6-C7-C8-T1)
Pronator teres muscle Flexor carpi radialis muscle Palmaris longus muscle Flexor digitorum superficialis muscle Flexor digitorum profundus muscles to thumb and index fingers Flexor pollicis longus muscle Pronator quadratus muscle Lumbricals to index and middle fingers Thenar muscles of thumb
Radial nerve (C5-C6-C7-C8-T1)
Triceps brachii muscle Anconeus muscle Brachioradialis muscle Extensor carpi radialis longus Extensor carpi radialis brevis Extensor digitorum Extensor digiti minimi Extensor carpi ulnaris Supinator Abductor pollicis longus Extensor pollicis longus Extensor pollicis brevis Extensor indicis
Ulnar nerve (C7-C8-T1)
Flexor carpi ulnaris muscle Ulnar/lateral half of Flexor digitorum profundus muscles Palmar interossie Morsal interossei Adductor pollic muscle Palmaris brevis muscle Hypothenar muscles Lumbricals to ring and little finger Passes through cubital tunnel between medial epicondyle of humerus and olecranon then between heads of FCU.
