Anatomy (Axilla and Brachial Plexus - 11/3) Flashcards
Axillary Sheath
Continuation of fascia associated with anterior/middle scalene muscles – continues laterally as tubular sheath surrounding nerves of brachial plexus/axillary artery (not axillary vein)
Anterior Wall of Axilla
Pec major, minor, clavipectoral fascia
Posterior Wall of Axilla
Subscapularis, teres major, Lat dorsi
Medial Wall of Axilla
First 4 ribs, intercostal muscles, upper part of serratus anterior
Lateral Wall of Axilla
Humerus, coracobrachialis, biceps brachii
Cervicoaxillary canal
Bound by clavicle, scapula, 1st rib. Contains axillary a/v, brachial plexus
Intercostobrachial nerve
Lateral branch of second intercostal nerve (T2), supplies lateral chest wall –> medial arm
Branches of Axillary Artery
1 - Superior Thoracic 2 - Thoracoacromial Trunk Lateral Thoracic 3 - Subscapular artery (-- circumflex scapular artery, thoracodorsal artery) Posterior Circumflex humeral artery Anterior circumflex artery
Lateral thoracic artery –>
Lateral portion of breast
Circumflex scapular artery pathway
From subscapular artery –> enter infraspinous fossa, form anastomosis w/ suprascapular artery
Thoracodorsal artery pathway
From subscapular artery –> join with thoracodorsal nerve –> latissimus dorsi
Posterior circumflex humeral artery pathway
Accompanies axillary nerve through quadrilateral space, encircles humerus to anastomose w/ anterior circumflex humeral artery
Posterior Triangle
Trapezius, sternocleidomastoid, clavicle (brachial plexus here + axilla)
5 Major branches of brachial plexus (from top to bottom)
Musculocutaneous Axillary Radial Median Ulnar
Branches from lateral cord
Lateral pectoral nerve
musculocutaneous nerve
lateral root –> median nerve (with medial root of medial cord)
Branches from posterior cord
upper/lower subscapular nerves
thoracodorsal nerve
axillary nerve
radial nerve
Branches from Medial cord
Medial pectoral nerve
medial brachial cutaneous nerve
medial antebrachial cut. nerve
ulnar
Medial root –> median nerve (with lateral root of lateral cord)
Thoracodorsal nerve innervates _______
Latissimus dorsi
Medial Pectoral nerve innervates
Pectoralis major and minor
Upper/Lower subscapular nerves innervates ____
subscapularis + Teres major
Lateral pectoral nerve innervates ________
pectoralis major
Lateral cord spinal nerve derivatives
C5,6,7
Posterior Cord spinal nerve derivatives
C5,6,7,8,T1 –> extensors! (except brachioradialis = forearm flexor)
Medial cord spinal nerve deri.
C8, T1
Musculocutaneous Nerve SCD
C5,6,7 (from lateral cord)
Median Nerve SCD
C5,6,7 (From Lateral cord) AND C8,T1 (from medial cord)
Ulnar nerve SCD
C8/T1
Axillary / Radial Nerves SCD
C5,6,7,8,T1 –> Extensors
Upper Brachial Plexus Injury
Erb-Duchenne Palsy
Injury to C5,C6 –> Supply lateral rotators (infraspinatus, teres minor)/Abductors of arm (supraspinatus, deltoid)
Increase in angle between neck and shoulder
Fall, delivery of baby
Adducted arm, medial roation or arm (hand faces backward), extended elbow
“Waiter’s Tip” Hand
Lower Brachial Plexus Injury
Klumpke Paralysis
Less common
Upper limb pulled up (falling and try to catch self, or delivery of baby)
Injury to C8-T1 –> Ulnar nerve - major influence of hand –> weakness/atrophy of hand muscles
Median nerve (also hand muscles)
“Claw” Hand
Medial brachial/antebrachial cutaneous nerves
Sensory nerves from medial cord of plexus - provide sensory innervation to medial areas of UE
Subscapularis
Inner surface of Scapula (subscapular fossa)
Medial aspect of scap –> Lesser tubercle of humerus
Rotator cuff - medial rotate the arm
Upper/lower subscapular nerves (from posterior cord of BP)
Latissimus Dorsi
Adduct arm, laterally rotate & extend arm Spinous processes T7-L5, iliac crest of spine, Inferior angle of scapula, thoracolumbar fascia --> intertubercular groove of humerus (lateral to teres major) Thoracodorsal nerve (middle subscapular nerve) from posterior cord of BP
Teres major
Adduct arm, medially rotate, extend arm
Attaches to humerus at intertubercular groove of humerus (medial to LD insertion) –> inferior aspect (posterior) of scapula
Lower subscapular nerve
Serratus anterior
Stabilizes scapula (protracts)
Scapular to anterior ribs
Long thoracic nerve
Where does axillary artery come from/go (as continuation)
Subclavian artery –> first rib = axillary artery –> 6 branches/3 parts d/t pec minor –> at inferior border teres minor = brachial artery
Where does axillary vein come from/go (as continuation)
Brachial + Basilic veins –> axillary vein –> first rib = subclavian vein
Axillary lymph nodes
Pectoral, subscapular, humeral –> central –> apical
What groups of muscles are supplied by the anterior and posterior divisions of the plexus?
Anterior division –> anterior compartment = flexors
Posterior division –> posterior compartment = extensors
What nerves associated with wrist drop? Crutches too long?
Radial nerve (off of posterior cord) - runs posteriorly through radial groove Wrist extensors don't work - wrist flexed (dropped)
Where is brachial plexus block performed?
Around axillary sheath