007 anatomy of the axilla and brachial plexus Flashcards
what is the axilla?
area of transition between the neck and the shoulder where nerve and vessels can pass through
describe the structure/shape of the axilla
- 4 walls
- a floor
- 1 inlet a the top
- bit like a pyramind
describe the structure and function of the axillary inlet/apex
- triangle opening at the top of the axilla
- sits between the lateral border of rib 1, the superior border of the scapula, and posterior border of the clavicle
- nerves and muscles go over rib 1 and through the axillary inlet to get to the shoulder/arm
what is the anterior boundary of the axilla?
- pectoralis major and minor
- subclavius muscle
- clavipectoral fascia (from clavicle to floor of axilla)
- lower margin of pectoralis major = anterior axillary fold
what is the medial boundary of the axilla?
- thoracic wall ( ribs, intercostal muscles)
- serratus anterior muscles
- long thoracic nerve and intercostobrachial nerve (lateral branch of the 2nd intercostal nerve and innervates skin on upper, medial side of arm)
what is the floor/base of the axilla?
- the skin of the armpit = where you palpate for swollen lymph nodes
what is the lateral wall of the axilla?
- intertubercular sulcus/bicipital groove of humerus
what is the posterior wall of the axilla?
- subscapularis muscle
- teres major msucle
- latissimus dorsi muscle
- long head of triceps
- latissimus dorsi and teres major = posterior axillary fold
what/ where is the posterior axillary fold?
- latissimus dorsi and teres major
what/where is the anterior axillary fold?
- lower margin of pectoralis major
what are the 4 gateways in the posterior wall?
- suprascapular foramen
- quadrangular space
- triangular space
- triangular interval
what is the suprascapular foramen and what are its boundaries?
- a pathway for suprascapular nerve = (through) and artery (above)
- bounded by the suprascapular notch and superior transverse scapula ligament
what is the quadrangular space and what are its boundaries?
- a pathway for the axillary nerve and posterior humeral circumflex artery
- bounded by the surgical neck of the humerus, inferior margin of teres minor, superior margin of teres major and lateral margin of long head of tricep
what is the triangular space and what are its boundaries?
- a pathway for the circumflex scapular margin
- bounded by the medial margin of long head of tricep, superior margin of teres major and inferior margin of teres minor
what is the triangular interval and what are its boundaries?
- a pathway for the radial nerve and profunda brachii artery
- bounded by the lateral margin of triceps, the shaft of the humerus and inferior margin of teres major
what are the 2 muscles in the axillary?
- coracobrachialis
- biceps brachii
what is the origin of biceps brachii?
- 2 heads
- long head = supraglenoid tubercle of scapula
- short head = coracoid process
what is the insertion of the biceps brachii?
- radial tuberosity of forearm and fascia of forearm via bicipital aponeurosis
what is the innervation of the biceps brachii?
musculocutaneous nerve (C5,6)
what is the action of biceps brachii?
- flexion of shoulder and elbow
- supination of forearm ( strongest supinator)
what is the origin of coracobrachialis?
- coracoid process
what is the insertion of coracobrachialis?
- medial side of humeral shaft (at level of deltoid tuberosity)
what is the innervation of coracobrachialis?
- musculocutaneous nerve (C5,6)
what is the action of coracobrachialis?
flexion of arm at shoulder and weak adduction
what is the main artery in the axilla?
axillary artery
how does the axillary artery change names in different areas of the body?
- clavicle = subclavian artery
- once crossed rib 1 = axillary artery
- halfway down humerus, at inferior margin of teres major = brachial artery
what are the 3 parts of the axillary artery and how many branches do they have?
1st part = just past 1st rib until pectoralis minor, 1 branch
2nd part = deep to pectoralis minor muscle, 2 branches
3rd part = past pectoralis minor muscle, until teres major inferior margin, 3 branches
what is the branch of the 1st part of the axillary artery and what does it supply?
- superior thoracic artery
- upper medial and anterior axillary walls
what are the 2 branches of the 2nd part of the axillary artery?
- thoracoacromial artery/trunk
- lateral thoracic artery
what does the thoracoacromial artery/trunk supply?
- clavicular, acromial, deltoid and pectoral branches (Cadavers Are Dead People)
what does the lateral thoracic artery supply?
- pectoralis minor
- serratus anterior
- lateral thoracic wall
what are the 3 branches of the 3rd part of the axillary?
- subscapular artery
- anterior humeral circumflex artery
- posterior humeral circumflex artery
what does the subscapular artery supply?
branches into circumflex scapular artery and thoracodorsal artery which supplies posterior and medial axilla walls
what does the anterior and posterior humeral circumflex artery supply?
glenohumeral joint, teres major and minor, deltoid muscle
- they anastomose together around the humerus
what is the trunk called arising from the right subclavian artery?
thryocervical trunk
what 2 arteries does the thyrocervical trunk (from the right subclavian artery) give rise to?
- transverse cervical artery
- suprascapular artery
describe the anastomoses arising from the suprascapular artery
suprascapular artery –> circumflex scapular artery –> subscapular artery –> axillary artery –> posterior circumflex humeral artery –> axillary artery
describe the anastomoses arising from the transverse cervical artery
transverse cervical artery –> dorsal scapular artery –> circumflex scapular artery –> subscapular artery –> axillary artery
what is the main vein in the axilla?
axillary vein
what does the axillary vein change its name to at different regions, and what is the main branch off the axillary vein?
- subclavian vein = until 1st rib
- axillary vein = below 1st rib (anterior to axillary artery)
- basilic vein = begins at lower margin of teres major muscle
main branch = cephalin vein off axillary vein superior to pectoralis minor and lies in the deltopectoral groove
what are the 5 groups of nodes in the axilla?
- lateral (humeral)
- pectoral
- subscapular
- central
- apical
20-30 in total
what areas drain into the axillary lymph nodes?
- entire upper limb, top areas of back, chest and lower neck
why is the breast relevant to the axilla?
- the mammary gland of the axilla sometimes wraps underneath the armpit, entering the axilla
- therefore if a patient has breast cancer, it may be found in the axilla/armpit
what is a plexus?
- it connects more than one spine root to a single peripheral nerve
where does the brachial plexus originate from?
- ventral rami of C5-T1
what type of plexus is the brachial plexus and what does it innervate?
- somatic plexus
- provides all somatic motor and sensory innervation to upper limb, except to the trapezius and patch of skin near the axilla
where to and from does the brachial plexus carry sympathetics?
- to blood vessels, erector pilli muscles and sweat glands
- from T2-6
where do the roots of the brachial plexus run through?
between anterior and medius scalene
where do the trunks of the brachial plexus run?
- beneath the 1st rib, along subclavian artery
where do the divisions, cords and terminal nerves of the brachial plexus run through
- in the axilla, each one = a part of the axillary artery (1,2,3)
how many roots of the brachial plexus are there and what are they called?
5 = C5,6,7,8, T1
how many trunks of the brachial plexus are there and what are they called?
3 = upper, middle, lower
how many divisions are there of the brachial plexus and what are they called?
6 = 3 anterior (outer 3), 3 posterior (middle 3)
how many cords are there in the brachial plexus and what are they called?
3 = lateral, posterior, medial
how many terminal nerves are there in the brachial plexus and what are they called?
4 = musculocutaneous nerve, median nerve, radial nerve, ulnar nerve
what are 3 branches off the roots of the brachial plexus?
- dorsal scapular nerve (C5) = rhomboid major and minor muscles, and part of levator scapulae
- long thoracic nerve (C5-7)= serratus anterior
- contribution to phrenic nerve (C5)
what are the 2 branches off the trunks of the brachial plexus?
= off the superior trunk
- suprascapular nerve = suprascapular and infraspinatus muscle
- nerve to subclavius
what are the medial cord branches (C8-T1)?
-medial pectoral nerve (pectoralis major and minor)
- medial brachial cutaneous nerve ( sensory innervation to medial side of distal part of arm)
- medial antebrachial cutaneous ( sensory innervation to medial side of forearm)
what are the lateral cord branches (C5-7)?
- lateral pectoral nerve = pectoralis major
what are the posterior cord branches?
- axillary nerve (C5-6) = deltoid, teres minor, skin over upper lateral part of arm
- superior subscapular nerve (C5-6) = subscapularis
- thoracodorsal nerve (C6-8) = latissimus dorsi
- inferior subscapular nerve (C5-6) = subscapularis, teres major
what cord does the musculocutaneous nerve arise from?
lateral cord (C5-7)
what does the musculocutaneous innervate?
- muscles in anterior part of arm (coracobrachialis, brachialis, biceps brachii)
- sensory innervation of forearm
what cord does the median nerve arise from?
lateral cord (C5-7) and medial cord (C8,T1)
what does the median nerve innervate?
- flexor muscles in anterior compartment of forearm (except flexor carpi ulnaris and part of flexor digitorum profundus)
- thenar muscles
- lateral lumbricals in hand (digits 3,4)
- sensory innervation of lateral part of palm and digits, 5,4,3, and 1/2 of digit 2
what is the musculocutaneous nerve called past the biceps?
- lateral cutaneous nerve
what are the branches off the median nerve?
- anterior interosseous nerve = supplies deep muscles in anterior forearm
- palmar cutaneous nerve = innervates skin on parts of the hand
what does the palmar cutaneous branch innervate?
- lateral palm and thumb anterior
what does the digital cutaneous branch innervate?
- fingertips of lateral 3.5 digits and lateral 2 lumbricals
what cord does the ulnar nerve arise from?
- medial cord (C7,8 T1)
what does the ulnar nerve innervate?
- muscles of hand other than what median nerve innervates ( thenar and lateral 2 lumbricals)
- flexor carpi ulnaris and medial half of flexor digitorum
- sensory innervation of medial 1.5 fingers and palm area ( what median nerve doesn’t)
what are the 4 branches off the ulnar nerve?
- muscular branch = muscles in anterior forearm
- palmar branch = medial anterior palm
- superficial branch = medial anterior 1.5 fingers
- dorsal = branch = medial posterior palm and 1.5 fingers
what cord does the radial nerve arise from?
- posterior cord (C5-T1)
what does the radial nerve innervate?
- all muscles in posterior part of arm
- sensory innervation of most of posterior forearm, posterior medial palm, proximal posterior 3.5 fingers
what are the 5 branches of the radial nerve?
- lower lateral cutaneous nerve = lateral upper arm below deltoid
- posterior cutaneous nerve of arm and forearm = posterior upper arm and strip down posterior forearm
- superficial branch = anterior palm and lateral 3.5 digits
- deep branch = muscles in posterior forearm = then branches off to posterior interosseous nerve
what is a dermatome?
- an area of skin supplied by a single spinal cord level
what are the upper limb dermatomes and how are they arranged?
- C3-T2
- arm out straight and half pronated
- arm split halfway
- top of arm =C3,C4, C5, C6 (thumb), C7 (fingers 2-4), C8 (pinky finger), then lower side of the arm, T1, T2 (armpit)
where do you test for C5?
upper lateral arm
where do you test for C6?
pad of thumb
where do you test for C7?
pad of index finger
where do you test for C8?
pad of pinky
where do you test for T1?
medial elbow
what nerve innervates the top of the shoulder skin?
- supraclavicular nerve (C3,4)
what nerve innervates the lateral pad of the shoulder skin (regimental badge)?
- axillary nerve, superior lateral cutaneous nerve of arm branch(C5,6)
what nerve innervates the medial skin of the arm under the armpit?
- intercostobrachial nerve (T2)
what nerve innervates the lateral skin of the elbow?
- radial nerve, inferior lateral cutaneous nerve of arm branch (C5,6)
what nerve innervates the anterior front and medial skin of the forearm?
- branches of the medial cord = medial cutaneous nerve of arm and forearm (C8,T1)
what nerve innervates the anterior, lateral skin of the forearm?
- musculocutaneous nerve, lateral cutaneous nerve of the forearm branch (C5,6)
what nerve innervates the middle posterior part of the arm and forearm?
- radial nerve, posterior cutaneous nerve of arm (C5,6,7,8)
what innervates the medial palm of hand and medial 1.5 digits(posterior and anterior)?
ulnar nerve (C8,T1)
what innervates the anterior middle palm, anterior lateral 3.5 digits and posterior tips of digits 5-2?
median nerve (C6,7,8)
What innervates the thumb and the posterior medial surface of hand?
- radial nerve = superficial branch (C6,7,8)
What is Erb’s palsy characterised by?
- “waiters tip”
- adducted and medially rotated arm, extended elbow and pronated forearm, with fingers in holding shape (waiters tip)
what is Erb’s palsy caused by?
- damage to C5,6
- traumatic lateral neck bending e.g. childbirth or falling on shoulder/neck
what nerves can be damaged in Erb’s palsy?
- suprascapular, axillary, dorsal scapular, musculocutaneous, radial
what is Klumke’s palsy characterised by?
- claw hand, no 4th and 5th interphalangeal extension
what is Klumpke’s palsy caused by?
- damage to root of C8 and T1
- traumatic hyperabduction of arm e.g. hanging from a tree, or arm pulled in childbirth
- paralysed most intrinsic hand muscles
what nerve is most often damaged in Klumpke’s palsy?
ulnar nerve
what is wrist drop/saturday night palsy characterised by?
- loss of extensors, the wrist can no longer extend upwards, so flops down
- loss of sensation on posterior forearm, elbow and dorsum of hand
what is wrist drop/saturday night palsy caused by?
- loss of extensors (triceps, brachioradialis, supinator and extensors of wrist and fingers)
- fracture of humerus, falling asleep with arm over the back of a chair, improper use of crutches
what nerves are most often damaged in wrist drop/saturday night palsy?
- posterior cord and radial nerve
what is benediction hand/pope’s blessing characterised by?
- thumb, and digits 2,3 cannot flex so if you make a fist digits 1,2,3 and extended like a pope’s blessing sign
what is benediction hand/pope’s blessing caused by?
- fracture of humerus, lacerations at wrist proximal to flexor retinaculum
- loss of finger and wrist flexors, thenar muscles, and 1,2 lumbricals
what nerve is damaged in benediction hand/pope’s blessing?
median nerve
what is carpal tunnel syndrome characterised by?
- numbness, tingling, pain or weakness in palm and digits 1-4
- not able to grip
what is carpal tunnel caused by?
- compression of the median nerve in the carpal tunnel
- e.g. repetitive straining movements or injury at the wrist
what nerve is affected in carpal tunnel syndrome?
- median nerve
what are the clinical signs of injury to the radial nerve?
- wrist drop = triceps brachii and muscles of posterior forearm weakened
- loss of sensation over lateral and posterior upper arm, posterior forearm and dorsal surface of lateral 3.5 digits
what are the clinical signs of injury to the median nerve?
- carpal tunnel syndrome ( numbness, tingling and loss of grip)
-hand of benediction/pope’s blessing = flexors and pronators in arm paralysed, so arm is constantly supinated and extended/ weak flexion, and digits 1-3 are extended
what are the clinical signs of injury to the median nerve?
- flexor carpi ulnaris and medial half of flexor digitorum profundus and interossei paralysed, no abduction or adduction of fingers
- paralysis of 2 medial lumbricals = no flexion of digits 4,5
- ulnar claw
- loss of sensation
- cannot grip
