Axilla and Brachial Plexus Flashcards
What is the axilla?
pyramidal-shaped region between arm and chest
What are the borders of the axilla?
- anterior wall - pectoralis major and minor muscles
- posterior wall - latissimus dorsi, teres major, and subscapularis muscles
- medial wall - seratus anterior muscle
- lateral wall - intertubercular sulcus of humerus
- base - skin and fascia of armpit
What are the contents of the axilla?
- axillary sheath - axillary artery and brachial plexus
- axillary vein and lymphatics (outside sheath)
- fat and connective tissue
- cutaneous nerves
What are the 5 principal groups of lymph nodes in the axilla? What do they drain?
- pectoral - anterior thoracic wall and most of breast
- subscapular - posterior thoracic wall and scapular region
- humeral - upper limb except for the portion along the cephalic vein
- central - from all 3 above to apical
- apical - all + proximal cephalic vein nodes
What are the 3 parts of the axillary artery and what branches does each part give?
- 1st part - between first rib and pectoralis minor muscle
- superior thoracic artery
- 2nd part - deep to pectoralis minor muscle
- thoracoacromial artery
- lateral thoracic artery
- 3rd part - between pectoralis minor and teres major muscles
- subscapular artery
- anterior circumflex humeral artery
- posterior circumflex humeral artery
What rami compose the brachial plexus?
ventral rami C5-T1
What does the brachial plexus supply?
all muscles of the upper limb except trapezius muscle
Where does C1-C8 nerves emerge in respect to their vertebrae of the same name?
- C1-C7 emerge above C1-C7 vertebrae
- there is no C8 vertebrae so C8 emerges below C7 and above T1 vertebrae
What is the structure of the brachial plexus? (What are the sections of the brachial plexus?)
- rami (5) - emerge in upper neck
- trunks (3) - form in lower neck
- divisions (6) - split off behind clavicle
- cords (3) - form in axillary region
- branches (5) - split off in upper arm
What spinal nerves form the musculocutaneous nerve?
C5, C6, C7
What spinal nerves form the median nerve?
C5-T1
What spinal nerves form the ulnar nerve?
C8, T1
What spinal nerves form the axillary nerve?
C5, C6
What spinal nerves form the radial nerve?
C5-T1
In the brachial plexus, what is formed by the joining of the C5 and C6 rami?
upper trunk
In the brachial plexus, what is formed by the joining of the C8 and T1 rami?
lower trunk
In the brachial plexus, what is formed by the joining of the upper and middle trunks?
lateral cord
In the brachial plexus, what is formed by the joining of the posterior divisions of the upper, middle, and lower trunks?
posterior cord
In the brachial plexus, what is the name of the trunk formed by the C7 rami?
middle trunk
In the brachial plexus, what is formed by the anterior division of the lower trunk?
medial cord
In the brachial plexus, what is formed by the joining of the lateral and medial cords?
median nerve
In the brachial plexus, what is formed only by the lateral cord?
musculocutaneous nerve
In the brachial plexus, what is formed only by the medial cord?
ulnar nerve
In the brachial plexus, what is formed by the posterior cord?
radial nerve and axillary nerve
What is the course of the musculocutaneous nerve?
- formed from the lateral cord
- passes through coracobrachialis muscle
- enters the biceps brachii and brachialis muscles
- innervates coracobrachialis, biceps, and half of the brachialis muscles
What is the “major nerve of the anterior arm”?
musculocutaneous nerve
What is the course of the median nerve?
- formed from 1/2 lateral cord and 1/2 medial cord
- passes medial to arm muscles
- innervates most of the anterior forearm, 3 thenar eminence muscles, and first 2 lumbricals in hand
What is the “major nerve of the anterior forearm”?
median nerve
What is the course of the ulnar nerve?
- formed from medial cord
- runs behind the medial epicondyle
- innervates most of the muscles of the hand, flexor carpi ulnaris muscle, and ulnar 1/2 of the flexor digitorum profundis muscle in forearm
What is the “major nerve of the hand”?
ulnar nerve
What is the course of the axillary nerve?
- formed from posterior cord
- circles behind humerus in quadrangular space
- innervates deltoid and teres minor muscles
What is the course of the radial nerve?
- formed from posterior cord
- passes posterior to humerus in radial groove and within triangular interval
- innervates all muscles in posterior arm and posterior forearm and 1/2 of brachialis muscle
What is the “major nerve of the posterior arm and forearm”?
radial nerve
What nerves make up the upper plexus? What spinal nerves contribute to them?
- dorsal scapular nerve - C5
- long thoracic nerve - C5-C7
- suprascapular nerve - C5-C6
What does the dorsal scapular nerve supply?
rhomoboid and levator scapulae muscles
What does the long thoracic nerve supply?
serratus anterior muscle
What does the suprascapular nerve supply?
supraspinatus and infraspinatus muscles
What are the two pectoral nerves? What spinal nerves contribute to them?
- lateral pectoral nerve - C5-C7
- medial pectoral nerve - C8-T1
What does the lateral pectoral nerve supply?
pectoralis major muscle
What does the medial pectoral nerve supply?
pectoralis major and minor muscles
What nerves make up the lower plexus? What spinal nerves contribute to them?
- upper subscapular nerve - C5-C6
- thoracodorsal nerve - C6-C8
- lower subscapular nerve - C5-C6
What does the upper subscapular nerve supply?
subscapularis muscle
What does the thoracodorsal nerve supply?
latissimus dorsi muscle
What does the lower subscapular nerve supply?
subscapularis and teres major muscles
What are the additional nerves (not including those of the upper/lower plexuses or pectoral region) that branch off of the brachial plexus? What spinal nerves contribute to them?
- nerve to subclavius muscle - C5-C6
- medial brachial cutaneous nerve - C8-T1
- medial antibrachial cutaneous nerve - C8-T1
What does the nerve to subclavius supply?
subclavius muscle
What does the medial brachial cutaneous nerve supply?
sensory to medial arm
What does the medial antibrachial cutaneous nerve supply?
sensory to medial forearm
