The Axilla (Armpit)
▪ Is a fat-filled, pyramid-shaped space between the
upper part of the arm and the side of the chest.
▪ Forms an important passage for nerves, blood,
and lymph vessels as they travel from the root
of the neck to the upper limb.
▪ It has:
Apex
▪The upper end of the axilla.
▪Directed into the root of the neck.
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▪Boundedaries:
 Infront by the clavicle,
 Behind by the upper border of the scapula,
 Medially by the outer border of the first rib.
Base (the lower end)
▪Boundedaries
 In front by the anterior axillary fold,
 Behind by the posterior axillary fold, and
 Medially by the chest wall.
*The base of axilla is formed by the skin stretching
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between the anterior and posterior walls.
Walls
▪Anterior wall:
The pectoralis major, subclavius, and
pectoralis minor muscles.
▪Posterior wall:
The subscapularis, latissimus dorsi, and teres
major muscles from above down.
▪Medial wall:
The upper four or five ribs and the
intercostal spaces covered by the serratus
anterior muscle.
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▪The lateral wall
Narrow and formed entirely by the
intertubercular sulcus of the humerus.
The pectoralis major muscle of the anterior
wall attaches to the lateral lip of the
intertubercular sulcus.
The teres major and latissimus dorsi muscles
of the posterior wall attach to the medial lip
and floor of the intertubercular sulcus,
respectively.
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▪The posterior wall
−Its bone framework is formed by the costal
surface of the scapula.
−Muscles of the wall are:
The subscapularis muscle.
The distal parts of the latissimus dorsi and
teres major muscles.
The proximal part of the long head of the
triceps brachii muscle.
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The posterior wall
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The floor
The axilla is formed by fascia and a dome of
skin that spans the distance between the
inferior margins of the walls.
It is supported by the clavipectoral fascia.
Inferiorly, structures pass into and out of the
axilla immediately lateral to the floor where
the anterior and posterior walls of the axilla
converge and where the axilla is continuous
with the anterior compartment of the arm.
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Contents of the axilla
▪Axillary vessels:
Axillary artery and vein
▪Axillary lymph nodes and vessels
▪The brachial plexus.
▪Adipose and areolar tissue.
▪Lateral cutaneous branches of the intercostal
nerves.
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Axillary artery
▪Begins at the lateral border of the first rib as a
continuation of the subclavian artery.
▪Ends at the lower border of teres major muscle
after which it becomes brachial artery.
▪The artery is closely related to the cords of the
brachial plexus and their branches and is
enclosed with them in a connective tissue sheath
called the axillary sheath.
▪Supplies the walls of the axilla and related
regions, and continues as the major blood supply
to the more distal parts of the upper limb.
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Divided into three parts:
▪First or proximal part: between the first rib and
the medial border of pectoralis minor.
▪Second or posterior part: behind or posterior
to the muscle.
▪Third or distal part: between the lateral border
of pectoralis minor and the lower border of
teres major.
Each of these parts gives branch to one, two
and three arteries respectively.
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First Part of the Axillary Artery
Branches
Superior thoracic artery:
▪Supplies the muscles and the wall of the thorax
in the upper part of the pectoral region.
▪Forms anastomosis with the intercostal and the
internal thoracic arteries.
**Sometimes the superior thoracic artery may
arise from the thoracoacromial artery.
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Second part of axillary artery:
Branches
Thoracoacromial artery:
▪Gives rise to the following four branches:
A. Pectoral branch
B. Acromial branch
C. Clavicular branch
D. Deltoid branch
Lateral thoracic artery:
▪Descends to the lateral thoracic wall along the
lateral border of the pectoralis minor muscle.
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Third part of axillary artery:
Branches
Subscapular artery:
▪Descends along the lateral border of the scapula
and divides in to thoracodorsal and circumflex
scapular arteries.
✓The circumflex scapular artery forms
anastomosis with the suprascapular artery and
the deep and superficial branches of the
transverse cervical artery in the posterior part
of the scapula forming the so called scapular
anastomosis.
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▪The thoracodorsal artery runs with the
thoracodorsal nerve to the latissimus dorsi m.
Anterior circumflex humeral artery:
▪A small branch that runs dorsally anterior to the
surgical neck of the humerus.
Posterior circumflex humeral artery:
▪It courses posteriorly around the surgical neck of
the humerus with the axillary nerve and passes
through the quadrangular space.
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Arterial Anastomosis Around Scapula
(scapular anastomosis)
▪Is principally formed between the branches of
the first part of the subclavian and the third part
of the axillary arteries.
▪Takes place at two sites:
Around the body of scapula:
▪It occurs between the
A)Suprascapular artery, a branch of the
thyrocervical trunk.
B)Circumflex scapular artery, a branch of the
subscapular artery.
C)Deep branch of the transverse cervical artery,
a branch of the thyrocervical trunk.
Over the acromion process:
▪Occurs between the
(A)Acromial branch of the thoraco-acromial
artery,
(B)Acromial branch of the suprascapular artery,
and
(C)Acromial branch of the posterior circumflex
humeral artery.
Scapular anastomosis
Axillary vein
▪Is formed at the lower border of the teres
major muscle by the union of the venae
comitantes of the brachial artery and the basilic
vein.
▪It runs upward on the medial side of the
axillary artery and ends at the lateral border of
the first rib by becoming the subclavian vein.
▪Receives tributaries, which correspond to the
branches of the axillary artery, and the cephalic
vein.
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Lymph Nodes of the Axilla
▪The axillary lymph nodes (20 to 30 in number).
▪Drain lymph vessels from:
▪The lateral quadrants of the breast.
▪The superficial lymph vessels from:
 The thoracoabdominal walls above the level of the
umbilicus, and the vessels from the upper limb.
▪The lymph nodes are arranged in groups.
Anterior (Pectoral) group:
 Lying along the lower border of the pectoralis
minor behind the pectoralis major.
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Receive lymph vessels from the lateral
quadrants of the breast and superficial vessels
from the anterolateral abdominal wall above
the level of the umbilicus.
Posterior (Subscapular) group:
Lying in front of the subscapularis muscle.
Receive superficial lymph vessels from the
back, down as far as the level of the iliac
crests.
Lateral group(Humeral):
 Lying along the lateral wall of the axilla
medial to the axillary vein.
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 Receive nearly all of the lymph vessels of the
upper limb (except that carried by the
lymphatic vessels accompanying the cephalic
vein, which drain to the apical axillary
nodes).
Central group:
 In the center of the axilla in the axillary fat.
 Receive lymph from the above three groups.
Apical group:
 At the apex of the axilla at the lateral border
of the first rib.
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 Receive the efferent lymph vessels from all
the other axillary nodes.
Infraclavicular (deltopectoral) group:
−These nodes are not strictly axillary nodes
because they are located outside the axilla.
−They lie in the groove between the deltoid
and pectoralis major muscles.
−Receive superficial lymph vessels from the
lateral side of the hand, forearm, and arm.
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**The efferent vessels from apical nodes drain
into the subclavian lymph trunk.
 On the left side, this trunk joined by the
jugular and bronchomediastinal trunks to
form the thoracic duct.
 On the right side, it joins into the right
lymph trunk.
 Alternatively, the lymph trunks may drain
directly into one of the large veins at the
root of the neck.
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The Brachial plexus
▪At the root of the neck.
▪Is mainly formed by the ventral rami of the
spinal nerves C5 -T1, but sometimes C4 and T2
may also contribute.
If the contribution of C4 is larger than that of
T2, then the plexus C4 – C8 = pre-fixed and if
the contribution of T2 is larger than that of C4,
the plexus thus formed by C5 - T2 =post-fixed.
▪The plexus can be divided into roots, trunks,
divisions, cords and Branches.
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Roots
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Trunks
1)Upper (superior) trunk: formed by roots C5 & C6.
2)Middle trunk: formed by the root C7.
3)Lower (inferior) trunk: formed by roots C8 & T1.
Divisions
▪Each trunk divides into anterior & posterior
divisions and they lie behind the clavicle.
Cords
 Lateral cord: formed by the union of anterior
divisions of the upper and middle trunks.
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 Medial cord: formed by the continuation of
anterior division of the lower trunk.
 Posterior cord: formed by union of the
posterior divisions of all three trunks.
Thus, the cords of the plexus have the
relationship to the second part of the axillary
artery that is indicated by their names.
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Branches of the brachial plexus
From the roots
Long thoracic nerve/nerve to serratus anterior
(C5, C6,and C7).
Dorsal scapular nerve/nerve to rhomboids(C5).
Levator scapulae, rhomboid major and
minor
*In addition, branches are given by the roots to
supply scalene muscles and longus colli (C5, C6,
C7, and C8) and there is contribution to phrenic
nerve (C5).
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Long thoracic nerve
Winged scapula
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From the trunks
 Suprascapular nerve (C5 and C6)
−The upper most branch of the trunk.
−Supplies the supraspinatus and infraspinatus
muscles, glenohumeral (shoulder) joint.
 Nerve to subclavius (C5 and C6)
−Innervates the subclavius muscle and the
sternoclavicular joint.
−Frequently it contributes fibres to the phrenic
nerve as accessory phrenic nerve.
Brachial plexus and its branches (SS = suprascapular nerve, NS = nerve to
subclavius, US = upper subscapular nerve, LS = lower subscapular nerve, T =
thoraco-dorsal nerve, DS = dorsal scapular nerve).
From the cords
From the lateral cord
 Lateral pectoral nerve (C5, C6, and C7).
−Supplies the pectoralis major muscle.
 Lateral root of median nerve (C5, C6, & C7).
−Joined by the medial root to form the
median nerve.
−The median nerve gives off no branches in
the axilla.
 Musculocutaneous nerve (C5, C6, and C7)
−Supplies the coracobrachialis muscle, and
leaves the axilla by piercing that muscle.
From the medial cord
 Medial pectoral nerve (C8 and T1).
− Supplies and pierces pectoralis minor muscle,
and supplies pectoralis major muscle.
 Medial cutaneous nerve of arm (T1).
− Supplies the skin on the medial side of the
arm.
 Medial cutaneous nerve of forearm (C8 & T1).
− Supplies the skin on the medial side of the
forearm.
Medial root of median nerve (C8 and T1).
−Join the lateral root of the median nerve to
form the median nerve.
 Ulnar nerve (C7, C8, and T1).
−Gives off no branches in the axilla.
From the posterior cord
 Radial nerve (C5, C6, C7, C8, and T1).
−The largest branch of the brachial plexus
and lies behind the axillary artery.
−It gives off branches to the long and medial
heads of the triceps muscle and the posterior
cutaneous nerve of the arm.
 Axillary nerve/circumflex nerve (C5 and C6).
− Runs through the quadrangular space being
related to the surgical neck of the humerus.
− Gives a motor supply to the deltoid and
teres minor muscles.
 Thoraco-dorsal nerve (C6,C7, and C8).
− Also called middle subscapular nerve for it
arises between the upper and lower
subscapular nerves.
▪Runs with the thoracodorsal vessels to the
latissimus dorsi muscle.
Upper subscapular nerve (C5 and C6).
−Supplies the teres minor muscle.
 Lower subscapular nerve (C5 and C6).
−Supplies the teres major muscle.
*Both nerves supply the upper and lower parts
of the subscapularis muscle.
Major Nerves of the Upper Limb
Axillary nerve
The musculocutaneous n.
Radial nerve.
Median nerve
Ulnar nerve
Injuries to Brachial plexus
▪Complete lesions involving all the roots of the
plexus are rare.
▪Incomplete injuries are common and are usually
caused by traction or pressure; individual nerves
can be divided by stab wounds.
1.Upper Lesions of the Brachial Plexus
(Erb-Duchenne Palsy)
▪Resulting from excessive displacement of the
head to the opposite side.
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−Causes excessive traction or even tearing of C5
and 6 roots of the plexus (upper trunk).
−Occurs in infants during a difficult delivery or in
adults after a blow to or fall on the shoulder.
−The suprascapular nerve, the nerve to the
subclavius, and the musculocutaneous and
axillary nerves all possess nerve fibers derived
from C5 and 6 roots and will therefore be
functionless.
Paralysis and atrophy of the deltoid, flexor
muscles and the long supinator muscles of the
arm,..
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▪The arm and hand then assume
the Waiter's tip position (the upper
limb hanging at the side, with
medial rotation and the palm
facing posteriorly).
Waiter's tip.
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2.Lower Lesions of the Brachial Plexus (Klumpke’s
Palsy)
▪Injuries to the lower segments C8 and Th1
(lower trunk).
▪Mainly the ulnar nerve is involved.
▪Caused by excessive abduction of the arm.
Manifested by:
− Paralysis of the small muscles of the hand and
flexors of the wrist (claw hand)
− Loss of sensation on the skin area innervated
by ulnar n.
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Injury to terminal branches of brachial plexus
Injury of radial nerve in the axilla
▪In the axilla the radial nerve may be injured by
the pressure of the upper end of crutch (crutch
palsy).
▪Characteristics
Loss of extension of elbow
Loss of extension of wrist = wrist drop
Loss of extension of digits.
Loss of supination in extended elbow
 Sensory loss on small area of skin over the
posterior surface of the lower part of the arm.
 Sensory loss along narrow strip on the back of
forearm.
 Sensory loss on the lateral part of dorsum of
hand at the base of thumb and dorsal surface
of lateral 3½ digits.
 More often, there is an isolated sensory loss
on the dorsum of hand at the base of the
thumb.
Wrist drop resulting from
radial nerve injury
Area of sensory loss in hand
following radial nerve injury
above the elbow
Injury of radial nerve in the radial/spiral groove
Causes:
 Midshaft fracture of humerus,
 Inadvertently wrongly placed intramuscular
injection,
 Direct pressure on radial
nerve by ….
Saturday night paralysis.
Note drunk lady falling asleep with arm
over the back of chair.
Characterstics:
Loss of extension of the wrist and fingers.
 Wrist drop.
 Loss of supination when the arm is extended.
 Sensory loss is restricted only to a variable
small area over the dorsum of hand between
the first and second metacarpals.
Injury of radial nerve at elbow
 Loss of extension of the wrist and fingers but
no wrist drop.
Pain over the extensor aspect of the forearm.
Injuries of the median nerve:
At the elbow:
Characteristics
 Loss of pronation,  paralysis of pronator
teres.
 Weak wrist flexion, paralysis of all the
flexors of forearm except medial half of FDP
and flexor carpi ulnaris.
 Adduction of wrist,  paralysis of FCR and
unopposed action of FCU and medial half of
FDP.
 No flexion is at the interphalangeal (IP) joints
of index and middle fingers.
 Loss of flexion of terminal phalanx of thumb,
due to paralysis of FPL
 Benediction deformity of the hand,
 Ape-thumb deformity,
 Loss of sensation in lateral half of the palm
and lateral 3½ digits and also on the dorsal
aspects of same digits.
Effects of the median nerve injury: A, benediction deformity of the
hand (benediction attitude of hand); B, ape-thumb deformity.
Area of sensory loss in hand following injury of the median nerve.
At the mid-forearm:
− The injury of median nerve at mid-forearm
results in pointing index finger due to paralysis
of radial head of FDS.
− Other signs and symptoms will be same as
those which occur in lesion at distal forearm
and wrist.
At wrist (distal forearm):
− At wrist, median nerve and its palmar
cutaneous branch may be injured just proximal
to the flexor retinaculum by deep lacerated
wounds (cut injury), e.g., suicidal cuts.
Characteristic clinical features in such a case will
be as follows:
− Ape-thumb deformity, due to paralysis of
muscles of thenar eminence.
− Loss of sensation on the lateral part of the
palm (including that over the thenar
eminence) and lateral 3½ digits including loss
of sensation on the dorsal aspect of these
digits.
In the carpal tunnel:
▪Compression of median nerve in the carpal
tunnel= carpal tunnel syndrome.
▪Feeling of burning pain or ‘pins and
▪
needles’ along the sensory distribution of
median nerve (i.e., lateral 3½ digits).
▪No sensory loss over the thenar
eminence
because skin over thenar eminence is
supplied by the palmar cutaneous branch
of the median nerve, which passes
superficial to flexor retinaculum.
▪Weakness of thenar muscles.
▪ ‘Ape-thumb deformity’ may occur, if
left untreated, due to paralysis of the
thenar muscles
Injuries of the ulnar nerve:
Effects of the ulnar nerve injury:
A, Ulnar claw hand;
B, Hollowing of skin in the first web space on dorsal aspect of
hand.
Sensory loss in the hand following ulnar nerve
injury: A, Palmar aspect; B, dorsal aspect