Axilla and Brachial Plexus

Question 1

Define the boundaries of the axilla

Answer 1

Anterior: pectoralis major and minor muscles
Posterior: latissimus dorsi, teres major, long head of triceps and subscapularis
Medial: lateral thoracic wall and serratus anterior
Lateral: intertubercular groove of the humerus

Question 2

List the contents of the axilla

Answer 2

1. Axillary artery and the brachial plexus of nerves
2. Axillary vein and lymphatics
3. lymph nodes and the lymphatics from the upper extremity, the breast, and even the upper abdominal wall
4. Fat

Question 3

What encases the axillary artery and vein and the brachial plexus?

Answer 3

axillary sheath

Question 4

Where is the apex of the axilla?

Answer 4

near the clavicle and first rib

Question 5

What is the floor of the axilla?

Answer 5

axillary skin fold

Question 6

Brachial Plexus:

1. What spinal cord levels?
2. What does it innervate?
3. Mnemonic for segments?

Answer 6

1. C-5 to T-1
2. ALL THE INNERVATION to the upper extremity (Small exception is the intercostobrachial sensory nerve from T-2)
3. “Read That Damn Cadaver Book” = roots, trunks, divisions, cords, and branches

Question 7

Name the 5 major nerve branches of the brachial
plexus and their cords:

Answer 7

1. musculocutaneous: lateral cord
2. median: lateral and medial cords
3. radial: posterior cord
4. axillary: posterior cord
5. ulnar: medial cord

Question 8

Name all branches of lateral cord

Answer 8

1. lateral pectoral nerve to the pectoralis MAJOR muscle
2. musculocutaneous nerve
3. LATERAL ROOT of the median nerve

Question 9

Name all the branches of the Medial Cord

Answer 9

1. medial pectoral nerve to both pectoral muscles
2. medial brachial cutaneous nerve
3. medial antebrachial cutaneous nerve
4. ulnar nerve
5. MEDIAL ROOT of the median nerve

Question 10

Name all the branches of the posterior cord

Answer 10

1. upper subscapular nerve
2. thoracodorsal nerve
3. lower subscapular nerve
4. radial nerve
5. axillary nerve

Question 11

Describe the location of different parts of the brachial plexus relative to the scalene
muscles, the first rib, and the axillary artery

Answer 11

• Brachial plexus passes between the anterior and middle scalenes.
• Brachial plexus is superior to the first rib; cords of the brachial plexus are at or inferior to the clavicle
• The cords of the brachial plexus (lateral, posterior and medial) are named by their anatomical relation to the axillary artery

Question 12

Which nerves leave the brachial plexus proximal to the divisions AND what do they innervate?

Answer 12

1. long thoracic nerve (to the serratus anterior)
   2, dorsal scapular nerve (to the rhomboids and some of the levator scapulae)
2. the suprascapular nerve (to supraspinatus and infraspinatus muscles)
3. the nerve to the subclavius muscle (not important)

Question 13

What does the axillary nerve innervate?

Answer 13

deltoid and teres minor muscles

Question 14

Name the arteries BEFORE and AFTER the axillary artery and at what locations the change occurs

Answer 14

subclavian artery becomes axillary artery at the lateral border of the first rib

axilla artery becomes the brachial artery at the inferior border of the teres major muscle

Question 15

What are the locations of the three parts of the axillary artery and what branches come off of each?

Answer 15

First branch is proximal to the pectoralis minor: superior thoracic (not important)

Second branch is posterior to pectoralis minor: thoracoacromial and the lateral thoracic

Third branch is distal to pectoralis minor: subscapular and the anterior and posterior circumflex
humeral

Question 16

Axillary vein:

1. merger of what two veins
2. where does it end
3. anatomical position to axillary artery (what if abducted)?

Answer 16

1. brachial and basilic veins
2. becomes subclavian vein at the lateral border of the 1st rib
3. lies anteromedial to the axillary artery in anatomic position and anteroinferior if the arm is abducted

Question 17

cephalic vein

1. where is it located?
2. What does it empty into?

Answer 17

1. major subcutaneous vein of the lateral upper extremity
2. empties into the axillary vein slightly lateral to the 1st rib, above the pectoralis minor

Question 18

What is the function of the lymphatic system?

Answer 18

Multiple one-way valves in these vessels permit flow only toward the central venous system

Lymph nodes serve to filter the fluid and are sites of immunologic activity

Question 19

Where does the lymph fluid travel to and where does it drain?

Answer 19

Most of the lymph fluid travels to the thoracic duct, which in turn drains into the left subclavian vein

Question 20

Define terms:

Lymphangitis

Lymphadenitis

Lymphadenopathy

Lymphedema

Chlye

Answer 20

Lymphangitis = inflammation of lymph vessels
Lymphade**_n**_itis = inflammation of lymph _**n_**odes

Lymphadenopathy = lymph node swelling or enlargement whether or not inflamed…often a result of cancer metastases

Lymphedema = Accumulation of lymph in interstitial spaces

Chlye = lymphatic fluid from the intestines involved in fat digestion and often
appears milky

Question 21

Which nerve travels on the lateral surface of the serratus anterior muscle (i.e. medial wall of the axilla)?

Answer 21

long thoracic