The axilla is the pyramidal space between the upper arm and thorax that contains neurovascular structures serving the upper limb. It has boundaries formed by muscles and provides passageways for structures to different regions. The axilla contains the axillary artery and its branches, axillary vein and tributaries, lymph nodes and vessels, and the brachial plexus nerves embedded in fat. Injuries to specific nerves like the median, ulnar, and musculocutaneous nerves can impact function of muscles innervated by those nerves.

1. AXILLA
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2. Axilla
• Is the pyramidal space inferior to glenohumeral joint and superior
to axillary fascia at the junction of arm and thorax.
• Provides a passageway or distribution center for the neurovascular
structures that serve the upper limb.
• From this distribution center, neurovascular structures pass:
1. Superiorly via the cervicoaxillary canal to/from the root of neck
2. Anteriorly via the clavipectoral triangle to the pectoral region,
3. Inferiorly and laterally into the limb itself,
4. Posteriorly via the quadrangular space to the scapular region,
5. Inferiorly and medially along the thoracic wall to the serratus
anterior and latissimus dorsi.
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4. Axillary boundaries
• The axilla has an apex, a base, and four walls,
three of which are muscular.
Apex
• Is the cervico-axillary canal
– passageway between the neck and the axilla
• bounded by
– 1st rib
– clavicle and
– superior edge of the scapula
• The arteries, veins, lymphatics, and nerves
traverse this superior opening of the axilla to pass
to or from the arm.
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6.  Base of the axilla or axillary fossa
• Is formed by
– Skin
– subcutaneous tissue, and
– axillary (deep) fascia extending from the arm to the thoracic wall (the 4th
rib level)
• forming the axillary fossa (armpit).
• Bounded by
– Anterior and posterior axillary folds
– Thoracic wall
– Medial aspect of the arm.
 Anterior wall
• Has two layers, formed by the pectoralis major and pectoralis minor
and the pectoral and clavicopectoral fascia associated with them.
• The anterior axillary fold the inferior most part of it
– is formed by the pectoralis major, as it bridges from thoracic wall to
humerus, and the overlying integument.
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8. Posterior wall
• Formed by
– scapula and subscapularis m.(chiefly)
– Teres major and latissimus dorsi(inferiorly)
Medial wall
• Formed by
– Thoracic wall (1st -4th ribs and intercostal muscles)
and
– Overlying serratus anterior.
Lateral wall
• Is a narrow bony wall formed by the
intertubercular groove of the humerus.
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9. Contents
1 -Axillary blood vessels (axillary artery and its
branches, axillary vein and its tributaries).
2 -Lymphatic vessels.
3 -Axillary lymph nodes.
 All embedded in a matrix of axillary fat.
4 –The cords and branches of brachial plexus, a
network of interlinked nerves that pass from the
neck to the upper limb.
• Proximally, the neurovascular structures are
ensheathed in a sleeve-like extension of the
cervical fascia, the axillary sheath.
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11. Axillary Artery
• Begins at the lateral border of the 1st rib as the
continuation of the subclavian artery
• Ends at the inferior border of the teres major,
where it becomes the brachial artery.
• Divided into three parts by the pectoralis minor:
A. The first part
 located between the lateral border of the 1st rib and
the medial border of the pectoralis minor
Has one branch, the superior thoracic artery.
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13. B. The second part
 lies posterior to pectoralis minor
 Has two branches - the thoracoacromial and lateral thoracic arteries - which pass medial
and lateral to the muscle, respectively.
• Deep to the clavicular head of the pectoralis major, thoracoacromial artery divides into
four branches
– acromial,
– deltoid,
– pectoral, and
– clavicular),
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15. C. Third part
 Extends from the lateral border of pectoralis
minor to the inferior border of teres major
 Has three branches.
1. Subscapular artery
 largest branch of the axillary artery.
2. Anterior circumflex humeral
3. Posterior circumflex humeral arteries
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16. Axillary Vein
• Lies initially on the anteromedial side of the axillary
artery, with its terminal part anteroinferior to the artery.
• Formed by the union of the brachial and the basilic vein
at the inferior border of the teres major.
• Has three parts that correspond to the three parts of the
axillary artery.
• Thus the initial, distal end is the third part, whereas the
terminal, proximal end is the first part.
• The axillary vein (first part) ends at the lateral border of
the 1st rib, where it becomes the subclavian vein.
• The veins of the axilla are more abundant than the
arteries, they are highly variable, and frequently
anastomose.
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19. Axillary Lymph Nodes
• The axillary lymph nodes are arranged in five
principal groups: pectoral, subscapular, humeral,
central, and apical.
• The groups are arranged in a manner that reflects
the pyramidal shape of the axilla.
• Three groups of axillary nodes are related to the
triangular base, one group at each corner of the
pyramid:
–Pectoral (anterior)
–Subscapular (posterior)
–Humeral (lateral)
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22. Pectoral (anterior) nodes
• consist of three to five nodes
• lie along the medial wall of the axilla, around the lateral
thoracic vein and the inferior border of the pectoralis
minor.
• receive lymph mainly from the anterior thoracic wall,
including most of the breast, especially the superolateral
(upper outer) quadrant and subareolar plexus.
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23. Subscapular (posterior) nodes
• consist of six or seven nodes
• lie along the posterior axillary fold and
subscapular blood vessels.
• receive lymph from the posterior aspect of
the thoracic wall and scapular region.
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25. Humeral (lateral) nodes
• consist of four to six nodes
• lie along the lateral wall of the axilla, medial and
posterior to the axillary vein.
• receive nearly all the lymph from the upper limb,
except that carried by the lymphatic vessels
accompanying the cephalic vein, which primarily
drain directly to the apical axillary and
infraclavicular nodes.
Efferent lymphatic vessels from these three
groups pass to the central nodes.
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26. Central nodes
• are three or four large nodes situated deep to the
pectoralis minor near the base of the axilla, in
association with the second part of the axillary artery.
• Efferent vessels from the central nodes pass to the
apical nodes.
Apical nodes
• located at the apex of the axilla along the medial side of
the axillary vein and the first part of the axillary artery.
• The apical nodes receive lymph from all other groups
of axillary lymph nodes as well as from lymphatics
accompanying the proximal cephalic vein.
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27. • Efferent vessels from the apical group of nodes
traverse the cervicoaxillary canal.
• These efferent vessels ultimately unite to form
the subclavian lymphatic trunk.
• The subclavian trunk may be joined by the
jugular and bronchomediastinal trunks on
the right side to form the right lymphatic
duct, or it may enter the right venous angle
independently.
• On the left side, the subclavian trunk most
commonly joins the thoracic duct.
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29. Brachial Plexus
Netter 2nd ed
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209 .
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Grant’s Dissector 13th ed
210 .
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211
There are three nerves that enter
the anterior compartment
1) musculocutaneous
2) median
3) ulnar
.
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The posterior compartment of
the arm is supplied by the radial
nerve
 It then continues into the
posterior group of forearm
muscles to supply them
.
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38. The musculocutaneous nerve
Lateral cord of brachial plexus (C5, 6, 7)
Pierces the coracobrachialis, continues between the biceps
brachii and brachialis
At the lateral border of the biceps brachii, it terminates as the
lateral cutaneous nerve of the forearm
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39. Musculocutaneous n.
(C5-C7)
Netter 2 ed
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219 .
nd
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40. Injury to Musculocutaneous Nerve
Injury to the musculocutaneous nerve in the axilla is usually
inflicted by a weapon such as a knife
Paralysis of coracobrachialis, biceps, and brachialis
Flexion of the elbow and supination of the forearm are
greatly weakened
Loss of sensation on the lateral surface of the forearm
Lateral cutaneous nerve of the forearm
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41. The ulnar nerve
Medial cord of the brachial plexus (C (7), 8, T1)
Runs medial to the brachial artery to the middle of the arm and
then posterior to the medial intermuscular septum, against the
medial head of the triceps brachii
Has no branch in the arm
At the elbow, it runs posterior to the medial epicondyle of the
humerus and into the forearm
Accompanied by superior ulnar collateral artery and the ulnar
collateral nerve
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42. Innervates the :
Medial half of the flexor digitorum profundus
Flexor carpi ulnaris
Elbow joint
Palmar and dorsal cutaneous branches arise proximal to the
wrist
The ulnar artery accompanies ulnar nerve in most of the forearm
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43. The ulnar nerve, in the hand
Passes between pisiform and hook of hamate, anterior to flexor
retinaculum and pisohamate ligament
Divides into deep and superficial branch
Covered by deep fascia
1) Superficial branch
- Gives cutaneous branches to medial 1 1/2 fingers) -
Communicates with the median nerve.
2) Deep branch
- supplies 3 hypothenar muscles and all short muscles of
hand, except for the 5 muscles innervated by median nerve
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46. Ulnar Nerve Injury
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Injury usually occurs in one of four places
Posterior to the medial epicondyle of the humerus (most
common)
In the cubital fossa formed by the tendinous arch
connecting the humeral and ulnar heads of the FCU
 At the wrist
In the hand
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47. The power of wrist adduction is impaired, and when an attempt
is made to flex the wrist joint, the hand is drawn to the lateral side
by the FCR in the absence of the balance provided by the FCU
Difficulty making a fist because, in the absence of opposition,
the metacarpophalangeal joints become hyperextended, and he
or she cannot flex the 4th and 5th fingers at the distal
interphalangeal joints when trying to make a fist. Furthermore,
the person cannot extend the interphalangeal joints when trying
to straighten the fingers
=Claw hand
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49. The median nerve
Derived from C(5), 6-8, T1
From lateral and medial cords of the brachial plexus, which unite
in the axilla lateral to the brachial artery
In proximal regions, the median nerve is immediately lateral to
the brachial artery
In more distal regions, the median nerve crosses to the medial
side of the brachial artery and lies anterior to the elbow joint
•No branch in the arm but may receive or give a branch to the
musculocutaneous nerve
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52. runs deep to the flexor digitorum superficialis and then deep to
the flexor retinaculum
Innervates the elbow, wrist joint and all flexor muscles of the
forearm, except the flexor carpi ulnaris and the medial 1/2 of flexor
digitorum profundus
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53. Runs through the carpal tunnel, in the midline of the skin crease of
the hand, on the deep surface of the flexor retinaculum
In the palm, it is deep only to the palmar aponeurosis
Divides into "recurrent" and digital branches
 Skin of the 3 1/2 lateral digits, & joints of the digits and local
vessels
Motor branches are carried by the recurrent branch
•Abductor pollicis brevis
•Opponens pollicis
•Flexor pollicis brevis (superficial part)
•1st and 2nd lumbricals by digital branches
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55. Lesions of the median nerve
Two places: the forearm and wrist
The most common site is where the nerve passes through the
carpal tunnel
Paralysis of thenar muscles and the first two lumbricals.
• Opposition of the thumb is not possible and fine control
movements of the 2nd and 3rd digits are impaired
• Sensation is also lost over the thumb and adjacent two
and a half fingers
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56. •Injury resulting from a perforating wound in the elbow region
•Loss of flexion of the proximal and distal interphalangeal
joints of the 2nd and 3rd digits
•Inability to flex the metacarpophalangeal joints of 2nd & 3rd
digits because digital branches of the median nerve supply
the 1st and 2nd lumbricals
Ape hand
•Deformity in which thumb movements are limited to flexion
and extension of the thumb in the plane of the palm
•Caused by the inability to oppose and by limited abduction
of the thumb
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57. The radial nerve
Continuation of the posterior cord (C 5-8, T1)
Runs posterior to the axillary then the brachial artery
Runs anterior to the long head of the triceps into the posterior
compartment of the arm
Runs in the spiral groove and then into the anterior
compartment between brachioradialis and brachialis
Lying on the capsule of the elbow joint and then the supinator
muscle
Divides into a superficial radial nerve (sensory) and the posterior
interosseous nerve (deep radial nerve - mostly motor)
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59. 239
The superficial radial nerve
Sensory continuation of the radial nerve distal to the origin of
posterior interosseous nerve
Deep to brachioradialis
Runs with the radial artery
Becomes cutaneous about 5 cm proximal to the styloid process of
the radius
.
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60. 240 11/13/2018 10:21 PM
The cutaneous innervation of the dorsum of the hand by the
radial nerve
Runs just short of the nail beds, which are usually innervated by
the median nerve (lateral 3 1/2) and ulnar nerve (medial 1 1/2)
The ulnar nerve innervates the medial 1 1/2 digit by the dorsal
cutaneous branch
The radial nerve innervates the lateral 3 1/2 digits.
Dr. Abebe M.
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61. Injury to Radial Nerve
Superior to the origin of its branches to triceps brachii
Paralysis of the triceps, brachioradialis, supinator, and
extensor muscles of the wrist and fingers
Loss of sensation occurs in areas of skin
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62. Injured in the radial groove, the triceps is usually not completely
paralyzed but only weakened because only the medial head is
affected
Muscles in the posterior compartment of the forearm
that are supplied by more distal branches of the radial
nerve are paralyzed
Wrist-drop (inability to extend the wrist and fingers at
the metacarpophalangeal joints)
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69. Posterior
antebrachial
cutaneous
skin of dorsum of wrist
Radial nerve
skin of dorsum of
thumb and 2 1/2 digits
as far as
thedistal interphalangeal joint
Ulnar nerve
ulnar 1 1/2 digits and
adjacent part of dorsum of hand
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Dors
um of Hand
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70. Ulna
r
nerv
e
- sensory to skin of ulnar 1 1/2 digits
- motor to musclesof hypothenareminence;ulnar
two lumbricals,7interossei;adductor pollicis
muscle
Medi
an
nerve
-sensoryto skinof palmaraspectof thumband2
1/ 2digitsincludingtheskinonthedorsalaspectof
the distal phalanges
-motor to musclesof thenareminence;radialtwo
lumbrical muscles
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Palm of hand
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251
Brachial plexus injuries
•Injuries to superior parts of the brachial plexus (C5 and C6)
•Usually result from an excessive increase in the angle between
the neck and the shoulder.
Occur in a person who is thrown from a motorcycle or a
horse and lands on the shoulder in a way that widely
separates the neck and shoulder
•Injury is apparent by the characteristic position of the limb
(waiter's tip position) in which the limb hangs by the side in
medial rotation
Occur in a newborn when excessive stretching of the
neck occurs during delivery
•As a result of injuries to the superior parts of the
brachial plexus (Erb-Duchenne palsy), paralysis of
the muscles of the shoulder and arm supplied by
C5& C6 occurs
.
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72. The usual clinical appearance:
 An upper limb with an adducted shoulder, medially rotated
arm, and extended elbow. The lateral aspect of the upper limb
also experiences loss of sensation
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74. •Injuries to inferior parts of the brachial plexus (Klumpke paralysis)
are much less common
May occur when the upper limb is suddenly pulled
superiorly for example, when a person grasps something to
break a fall or when a baby's limb is pulled excessively during
delivery
The short muscles of the hand are affected and a claw
hand results
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76. Segmental (dermatomal) innervation
C5 nerve - arm laterally
C6 nerve - forearm laterally and the thumb
C7 nerve - middle and ring fingers (or middle three fingers) and
the middle of the posterior surface of the limb
C8 nerve - little finger, the medial side of the hand, and the
forearm
T1 nerve - middle of the forearm to the axilla
T2 nerve - a small part of the arm and the skin of the axilla
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77. The cutaneous nerves of the arm and forearm
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The posterior cutaneous nerve of the arm (C5-C8), a branch of
the radial nerve
- skin on the posterior surface of the arm
The posterior cutaneous nerve of the forearm (C5- C8), a branch
of the radial nerve
- skin on the posterior surface of the forearm
The inferior lateral cutaneous nerve of the arm (C5, C6), a branch
of the radial nerve
- skin over the inferolateral aspect of the arm
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78. The lateral cutaneous nerve of the forearm (C6, C7), the terminal
branch of the musculocutaneous nerve
- Skin on the lateral side of the forearm
The medial cutaneous nerve of the arm (C8-T2) arises from the
medial cord of the brachial plexus
-Skin on the medial side of the arm
The intercostobrachial nerve (T2), a lateral cutaneous branch of
the 2nd intercostal nerve
- skin on the medial surface of the arm
The medial cutaneous nerve of the forearm (C8, T1) arises from
the medial cord of the brachial plexus
- Skin on the anterior and medial surfaces of the
forearm
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80. Reference materials
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