Lecture 19: axilla and brachial plexus Flashcards
What is axilla
First and largest of 3 n/v funnels in upper limb
Transmits vessels and nerves between thorax/neck and upper limb
Describe shape axilla
Pyramidal shape
Describe borders axilla
Apex at clavicle, scapula and rib1
Base formed by armpit skin
Ant/posterior and medial/lateral walls formed mainly by muscles of back, shoulder and chest (also shaft humerus)
Name the 4 things in axilla - contents of axilla
Axillary fasciae sheath with axillary artery, vein and brachial plexus
Axillary lymph nodes - major collection point lymphatic system
Tendons of coracobrachialis and biceps brachii (2x)
Adipose tissue
Describe vasculature of axilla and upper limbs - gen
One major artery -early branch aortic arch, changes name as moves
= subclavian —> Axillary—> brachial artery
Describe vasculature of axilla and upper limbs - subclavian artery
Under clavicle
Major early branch of aorta —> becomes Axillary artery
Describe vasculature of axilla and upper limbs - axilary artery
After passing under clavicle, inferior border clavicle - sits in armpit —> becomes brachial artery
Describe vasculature of axilla and upper limbs - brachial artery
After inferior border teres major
Travels and branches further into upper limb
Describe how axillary artery is divided
3 parts by pectoralis minor = medial, under (deep to) and lateral to the muscle
Each part has specific regions that its branches supply
What does first part of axillary artery supply
Pectoral muscles - minor and major, subclavius and serratus anterior (upper portions)
One branch
What does second part of axillary artery supply
Supplies clavicle, acromion, deltoids, pectoral muscles and serratus anterior
One major trunk
What does third part of axillary artery supply
Between pectoralis minor and inferior border teres major
Supplies scapula, (branch to) lats and proximal humerus (anterior and posterior circumflex numeral arteries- forms anastomosis around surgical neck of humerus, *recall, fractures)
Describe superficial veins = gen
Highly variable - with numerous tributaries to 2 main veins =
Cephalic (towards head in relation to embryonic limb) and
Basilic (basal - towards tail)
Has general patterns
Describe cephalic vein
Starts at dorsal Venous arch
Hand to shoulders/pectoral region
Dives deeper - at deltopectoral groove, drains deep into Axillary vein
(Equiv to greater saphenous)
Describe basilic vein
Starts at dorsal Venous arch
Points down - on pinky side
Dives into arm and travels with deeper brains then becomes Axillary vein
(Equiv to lesser saph)
Describe median cubital vein
Connection between cephalic and basilic veins
Describe median cubital vein - clinical correlate
Site of venipuncture - blood draws
Name all deep veins of axilla
Subclavian
Axillary
Cephalic
Basilic
Paired brachial veins (deep veins of upper limb)
Describe deep veins - gen
Anatomical variation but common = basilic vein (superficial) joining paired brachial veins (run deep with brachial artery) to form Axillary vein
What does cephalic vein drain into
Into axillary vein directly through clavipectoral fascia
Describe venae comitantes
Matching veins to arteries often paired in smaller, more distal vessels of the limbs
1 artery: 2 veins
Brachial plexus - describe word
Braid
Network of spinal nerves
Brachial plexus Derived from
Spinal nerves c5-t1
Brachial plexus Describe emergence
From neck between ant and mid scalenes
Passes deep to clavicle
Funnels through Axilla closely associated with Axillary artery (uses Axillary artery as scaffold)
Brachial plexus Provides what
Motor and sensory innervation to upper limb
From shoulder to fingertips
Describe basic organization
As spinal nerves emerge = combine and divide in various ways - bradining
To eventually form 4 terminal branches into distal upper limb
Describe basic organization - fromproximal to distal
Plexus organized into sections that reflect this braiding pattern
Describe basic organization - peripheral nerves
Branch off along sections
Describe basic organization - way to remember sections
Roots 5 —> trunks 3 —> divisions 6 —> cords 3 —> branches 5
= Read The Darn Cadaver Book or Really Thirsty? Drink Cold Beer
How can peripheral nerves be divided
Into those that emerge above and below clavicle =
Supraclavicular nerves from roots and trunks
Infraclavicular nerves from cords and branches
What section of basic organization has no peripheral nerves (branches)
Divisions - sits righ under clavicle
Name supraclavicular branches
Dorsal scapular nerve
Nerve to subclavius
Long thoracic nerve
Suprascapualr nerve
Describe supraclavicular branches
4 branches = from roots (c5-c7) and superior trunk
Deep to clavicle and neck structures
Dorsal scapular nerve
Root c5
To rhomboids and levator scapulae
Nerve to subclavius
Superior trunk - c5/c6
To subclavius
Suprascapular nerve
Superior trunk c5/c6
To supraspinatus and infraspinatus
Long thoracic nerve
Roots c5,6,7
To serratus anterior
Describe infraclavicular branches - from medial and lateral cord
Come from not overlapping roots
Lateral and medial cords on opposite sides Axillary
= medial and lateral pectoral nerves
Describe medial pectoral nerve
C8-t1
From medial cord
To pectoralis minor and pectoralis major (sternocostal part)
Describe lateral pectoral nerve
C5-c7
From lateral cord
To pectoralis major (clavicular part)
Describe infraclavicular branches - from posterior cord
Lies posterior to Axillary artery
Thoracodorsal nerve
Superior subscapualr nerve
Inferior subscapular nerve
Posterior cord = c5-t1
Describe thoracodorsal nerve
C6-c8
To latissimus Dorsi
Describe superior subscapular nerve
C5-c6
To subscapularis
Describe inferior sub scapular nerve
C5-c6
To subscapularis And teres major
Describe infraclavicular branches - terminal branches - Gen
In Axilla - near shoulder joint = the 3 cords split/joint once more to form 5 terminal branches
Wrapped around Axillary artery
Name the 5 terminal branches
Axillary
Musculocutaneous
Radial
Median
Ulnar
Describe shape of 3 terminal branches - arise from medial and lateral cords
= musculocuteanous, median, ulnar = form M on anterior aspect of Axillary artery
= landmark to help orient
Name terminal branches from medial and lateral cords
Musculocutaneous
Median
Ulnar
Musculocutaneous nerve levels
C5-c7
All lateral cord
Musculocutaneous nerve Pathway
Pierces coracobrachialis muscle
Travels between biceps brachii and brachialis succulents
Emerges arterial to biceps - above elbow = AS lateral cutaneous antebrachial nerve (ends cutaneously)
Musculocutaneous nerve Motor
To anterior compartment of arm (musculo)
Musculocutaneous nerve Sensory
To lateral anterior forearm (cutaneous)
median nerve levels
C6-t1
Mixed lateral and medial cords
median nerve Pathway
Travels down midline of arm
Next to brachial artery
Through cubital fossa —> into forearm
In centre of anterior forearm
Into hand through carpal tunnel towards palm and digits
median nerve Motor and sensory
To lateral aspects of anterior compartments of forearm and hand (lateral palm area)
ulnar nerve levels
C8-t1 (somtimes c7)
All medial cord
ulnar nerve pathway
Travels down medial arm
Posterior to medial epicondyle of humerus
Into medial forearm
Into medial hand through ulnar tunnel
ulnar nerve motor and sensory
To medial aspects of anterior compartments of forearm and hand (medial palm area)
Outside carpal tunnel, sensory to 2 digits (also this is the funny bone effect one)
Name terminal branches from posterior cord
Axillary
Radial
Axillary nerve level
C5-c6
Posterior cord
Axillary nerve Pathway
Travels inferior to lateral scapular Borer
Through quadrangular space with posterior circumflex numeral artery
Onto posterior aspect
Wraps around laterally —> surgical neck of humerus
Axillary nerve Motor
Deltoid
Teres minor
Axillary nerve Sensory
Inferior Deltoid region and shoulder joint
(Upper arm to lower shoulder region)
radial nerve levels
C5-t1
Posterior cord
Largest branch
radial nerve Pathway
Posterior to humerus in radial groove
Visible in triangular interval - with deep brachial artery (between 2 heads of triceps)
Then in posterior compartment of arm
Anterior to lateral elbow
In posterior compartment forearm - and into dorsal of hand
radial nerve Motor
Posterior compartments of arm and forearm
radial nerve Sensory
Posterior of arms and dorsum of hand - huge job
Quadrangular space borders
Teres minor
Teres major
Long and lateral heads of triceps
Qudrangular space Contents
Axillary artery and posterior humeral circumflex artery pass through
Triangular interval borders
Teres major
Long and lateral heads triceps
Triangular interval Contents
Radial nerve
Deep brachial artery
BOTH = VISIBLE IN INTERVAL BUT DO NOT PASS THROUGH IT
Describe cutaneous innervation from brachial plexus = gen
5 TERMInal branches provide most of limbs cutaneous innervtaion
But 2 additional sensory only nerves emerge from medial cord
Describe cutaneous innervation from brachial plexus = name areas
Axillary - c5,6 =shoulder ish
Radial nerve c5-t1 = lateral side, all the way down posterior lay
Musculocutaneous c5-c7 AS LATREAL ANTEBRACHIAL CUTANEOUS NERVE = mots of forearm anterior
+ new branches
Describe cutaneous innervation from brachial plexus = 2 new nerves from medial cord
Medial brachial cutaneous nerve - from medial cord c8-t1
Medial antebrachial cutaneous nerve - from medial cord c8-t1
= do medial sides ant and posterior
Brachial plexus injuries and cutaneous outcomes - set up
Spinal nerves from c5-t1 = contribute to all peripheral nerves of upper limb
Each spinal nerve = innervates specific region of skin =dermatome, does not align with cutaneous - sensory areas of individual peripheral nerves
Brachial plexus injuries and cutaneous outcomes - ex
median nerve (C6-T1) injury will
lead to loss of sensation in palm of hand
and lateral digit tips, while injury to C6 root
has more widespread loss of sensation
overlapping musculocutaneous n. (C5-C6-
C7), median n. (C6-T1 – esp. thumb area),
axillary n. (C5-C6), and radial n. (C5-T1)
Brachial plexus injuries and motor outcomes - set up
Each spinal levele contributes to innervation of a specific group of muscles = myotome
Brachial plexus injuries will have diff outcomes if Inury in peripheral or spinal nerve root
Brachial plexus injuries and motor outcomes - ex
injury to musculocutaneous n.
(C5-C7) impairs elbow flexion (biceps
brachii, brachialis) and to lesser extent,
shoulder flexion (biceps brachii,
coracobrachialis), while injury to C5 root
impairs not only these motions (because C5
contributes to musculocutaneous n.), but
also shoulder abduction and lateral rotation
(suprascapular n. (C5-C6) to supraspinatus,
axillary n. (C5-C6) to lateral deltoid)
Describe how medial and lateral pectoral nerves look
Get their names from their cords
Not relative anatomical positions on pectoral muscles =
Medial pectoral nerv looks more lateral than lateral pectoral nerve (on pectoralis minor)
Ulnar nerve sensory hand innervation
Posteromedial hand
C8-t1
Medial wrist, medial 1.5 digits anteriorly
median nerve sensory hand innervation
C6-t1
Lateral wrist, lateral 3.5 digits and tips digits 2-4
