Dissection of tDissection of the Axillahe Axilla

The The axillaaxilla, or armpit, is a pyramidshaped space between the uppe, or armpit, is a pyramidshaped space between the uppe

r part of the arm and the side of the chest.r part of the arm and the side of the chest.

Realize that the upper end, or apex, is directed into the root of the Realize that the upper end, or apex, is directed into the root of the

neck and is bounded anteriorly by the clavicle, posteriorly by the neck and is bounded anteriorly by the clavicle, posteriorly by the

upper border of the scapula, and medially by the outer border of tupper border of the scapula, and medially by the outer border of t

he first rib. The lower end, or base, is bounded anteriorly by the ahe first rib. The lower end, or base, is bounded anteriorly by the a

nterior axillary fold (formed by the lower border of the pectoralis nterior axillary fold (formed by the lower border of the pectoralis

major muscle), behind by the posterior axillary fold (formed by thmajor muscle), behind by the posterior axillary fold (formed by th

e tend of latissimus dorsi and the teres major muscle), and medialle tend of latissimus dorsi and the teres major muscle), and mediall

y by the chest wall.y by the chest wall.

Carefylly remove the axillary fascia and fat anCarefylly remove the axillary fascia and fat an

d identify the d identify the axillary lymph nodesaxillary lymph nodes. Understan. Understan

d that the axillary lymph nodes are divided up id that the axillary lymph nodes are divided up i

nto the following groups: nto the following groups:

(1)anterior or pectoral,(1)anterior or pectoral,

(2)posterior or(2)posterior or subscapular, subscapular,

(3)central group, (3)central group,

(4)lateral group, (4)lateral group,

(5)apical group.(5)apical group.

Note the areas that they drain. Note the areas that they drain.

Walls of the AxillaWalls of the Axilla. .

Identify the structures formiIdentify the structures forming the walls of the axilla:�ng the walls of the axilla:�

Anterior wallAnterior wall. .

This is formed by the pectoralis mThis is formed by the pectoralis m

ajor, pectoralis minor, clavipectoraajor, pectoralis minor, clavipectora

l fascia, and subclavius muscle (thl fascia, and subclavius muscle (th

e pectoral muscles and the clavipee pectoral muscles and the clavipe

ctoral fascia have already been rectoral fascia have already been re

moved).moved).

Posterior wallPosterior wall..

From above downward this wall is forFrom above downward this wall is for

med by the subscapularis, latissimus med by the subscapularis, latissimus

dorsi, and the teres major muscles.dorsi, and the teres major muscles.

Medial wallMedial wall. .

This is formed by the upper four or This is formed by the upper four or

five ribs and the intercostal spaces five ribs and the intercostal spaces

covered by the serratus anterior mcovered by the serratus anterior m

uscle.uscle.

Lateral wallLateral wall. .

This is formed by the coracobracThis is formed by the coracobrac

hialis and biceps muscles in the bhialis and biceps muscles in the b

icipital groove of the humerus.icipital groove of the humerus.

Axillary SheathAxillary Sheath. .

The axillary artery (but not the vein) and the The axillary artery (but not the vein) and the

brachial plexus are enclosed in a fascial sheatbrachial plexus are enclosed in a fascial sheat

h derived from the prevertebral layer of deep h derived from the prevertebral layer of deep

cervical fascia in the neck. Identify the sheatcervical fascia in the neck. Identify the sheat

h. Clean the axillartyh. Clean the axillarty artery and its branc artery and its branc

hes.hes.

Axillary ArteryAxillary Artery. .

This commences at the outer border of the first This commences at the outer border of the first

rib as a continuation of the subclavian artery. rib as a continuation of the subclavian artery.

Having passed through the axilla, it becomes tHaving passed through the axilla, it becomes t

he brachial artery at the lower border of the terhe brachial artery at the lower border of the ter

es major muscle. It ises major muscle. It is arbitrarily divided into tarbitrarily divided into t

hree parts by the pectoralis minor muscle that hree parts by the pectoralis minor muscle that

crosses it anteriorly.crosses it anteriorly.

Identify the following branches of the Identify the following branches of the

axillary artery: axillary artery:

11..Highest thoracic arteryHighest thoracic artery. .

This is a small artery that runs along tThis is a small artery that runs along t

he upper border of the pectoralis minohe upper border of the pectoralis mino

r to the thoracic wall.r to the thoracic wall.

22..Thoracoacromial arteryThoracoacromial artery. .

This pierces the clavipectoral fascia and imThis pierces the clavipectoral fascia and im

mediately divides into terminal branches. mediately divides into terminal branches.

3.3.Lateral thoracic arteryLateral thoracic artery. .

This runs along the lower border of the pectThis runs along the lower border of the pect

oralis minor to the thoracic wall.oralis minor to the thoracic wall.

4.4.Subscapular arterySubscapular artery..This runs along the lower border of the subsThis runs along the lower border of the subscapularis muscle. capularis muscle.

5.5.Anterior and posterior circumflex hAnterior and posterior circumflex humeral arteries.umeral arteries. These wind around the anterior and posterior These wind around the anterior and posterior

surface of the surgicalsurface of the surgical neck of the humerus, neck of the humerus, respectively.respectively.

Comfirm that the Comfirm that the cephalic veincephalic vein drains i drains i

nto the nto the axillary veinaxillary vein. .

Now transect and remove the axillary Now transect and remove the axillary

vein and its tributaries. vein and its tributaries.

Brachial PlexusBrachial Plexus. .

Identify and clean the branches of tIdentify and clean the branches of t

he brachial plexus. Note their close he brachial plexus. Note their close

relationship to the axillary artery.relationship to the axillary artery.

1.Identify the 1.Identify the musculocutaneous nervemusculocutaneous nerve

firstly as it pierces the coracobrachialis firstly as it pierces the coracobrachialis

muscle. muscle.

Note that this nerve supplies the muscle Note that this nerve supplies the muscle

prior to piercing it.prior to piercing it.

2.Follow the musculocutaneous nerve p2.Follow the musculocutaneous nerve p

roximally to the point where it arises frroximally to the point where it arises fr

om the om the lateral cordlateral cord of the plexus. of the plexus.

Identify the Identify the lateral root of the median nlateral root of the median n

erveerve on the lateral side of the axillary ar on the lateral side of the axillary ar

tery.tery.

3. Identify the 3. Identify the lateral pectoral lateral pectoral

nervenerve arising from the lateral arising from the lateral

cord of the plexus.cord of the plexus.

4. Identify the 4. Identify the medial rootmedial root of the of the mm

edian nerveedian nerve on the medial side of th on the medial side of th

e axillary artery. e axillary artery.

Follow the median nerve down the Follow the median nerve down the

lateral side of the axillary artery.lateral side of the axillary artery.

5. Follow the medial root of the median ner5. Follow the medial root of the median ner

ve proximally and identify the ve proximally and identify the medial cordmedial cord o o

f the plexus. f the plexus.

6.Identify the remaining branches of the med6.Identify the remaining branches of the med

ial cord, namely, ial cord, namely, the the medial pectoral nervemedial pectoral nerve, th, th

e e ulnar nerveulnar nerve, the , the medial cutaneous nerve of thmedial cutaneous nerve of th

e forarme forarm, and the , and the medial cutaneous nerve of thmedial cutaneous nerve of th

e arm.e arm.

77. The . The radial nerveradial nerve is a large nerve lying is a large nerve lying

posterior to the distal part of the axillary posterior to the distal part of the axillary

artery. artery.

Trace this nerve proximally and identify tTrace this nerve proximally and identify t

he axillary nerve, which is the other termihe axillary nerve, which is the other termi

nal branch of the posterior cord of the plenal branch of the posterior cord of the ple

xus.xus.

8. The upper and lower 8. The upper and lower subscapular nervessubscapular nerves and the and the thorthor

acodorsal nerveacodorsal nerve (middle subscapular nerve) arise from t (middle subscapular nerve) arise from t

he posterior cord of the plexus.he posterior cord of the plexus.

The upper subscapular nerveThe upper subscapular nerve supplies the upper part of supplies the upper part of

the subscapularis muscle, the lower subscapular nerve the subscapularis muscle, the lower subscapular nerve

may be traced to the lower part of the subscapularis mumay be traced to the lower part of the subscapularis mu

scle and the teres major muscle, and the thoracodorsal nscle and the teres major muscle, and the thoracodorsal n

erve (middleerve (middle subscapular nerve)supplies the latissimus subscapular nerve)supplies the latissimus

dorsi muscle.dorsi muscle.

Note that the medial cutaneous nerve of the arm usually Note that the medial cutaneous nerve of the arm usually

communicates with the communicates with the intercostobrachial nerveintercostobrachial nerve. This is . This is

the lateral cutaneous branch of the second intercostal nethe lateral cutaneous branch of the second intercostal ne

rve, which emerges from the second intercostal space. rve, which emerges from the second intercostal space.

Identify the Identify the long thoracic nervelong thoracic nerve as it runs down the medi as it runs down the medi

al wall of the axilla and supplies the serratus anterior mual wall of the axilla and supplies the serratus anterior mu

scle. Having identified all the structures in the axilla,carescle. Having identified all the structures in the axilla,care

fully clean them.fully clean them.

Study the origin of the Study the origin of the serratus anterior muserratus anterior mu

sclescle, which arises by eight digitations from t, which arises by eight digitations from t

he outer surface of the upper eight ribs. he outer surface of the upper eight ribs.

This is a large, flat muscle that runs posteriThis is a large, flat muscle that runs posteri

orly around the thoracic wall to beorly around the thoracic wall to be inserted inserted

into the anterior surface of the medial bordinto the anterior surface of the medial bord

er of the scapula.er of the scapula.

Clean the Clean the subscapularis musclsubscapularis muscl

ee and note that it arises from t and note that it arises from t

he anterior surface of the scaphe anterior surface of the scap

ula and is inserted into the lessula and is inserted into the less

er tuberosity if the humerus.er tuberosity if the humerus.

Follow the tendon of the Follow the tendon of the latissimus dorsilatissimus dorsi

musclemuscle to its insertion into the floor of the to its insertion into the floor of the

bicipital groove of the humerus. Clean the bicipital groove of the humerus. Clean the

teres major muscleteres major muscle and trace it to its inser and trace it to its inser

tion into the medial lip of the bicipital grotion into the medial lip of the bicipital gro

ove of the humerus.ove of the humerus.