The axilla is a pyramid-shaped space between the upper arm and chest. It contains nerves, blood vessels, lymph nodes, and fat. The boundaries include the clavicle, ribs, and muscles. The brachial plexus forms in the neck and provides motor and sensory innervation to the upper limb. It gives off branches in the axilla including the nerves that form its three cords surrounding the axillary artery. These cords supply the different regions of the upper limb.

1. AXILLA
By
ABDULMUJEEB
October 2, 2023 1

2. Definition
• It is a pyramid shaped space between the
upper part of the arm and the side of the
chest
• Important Nerves, Blood and Lymph
vessels travel through it from root of the
neck to the upper limb
October 2, 2023 2

3. Axilla is an irregularly shaped pyramidal space with:
Four walls
An inlet (apex)
A floor (base)
October 2, 2023 3

4. Boundaries of
the Axilla
 Apex:
 Is directed upwards &
medially to the root of
the neck.
 It is called Axillary inlet/
Cervicoaxillary canal.
 It is bounded, by 3
bones:
• Clavicle anteriorly.
• Upper border of the
scapula posteriorly.
• Outer border of the
first rib medially.
C
L
A
V
I
C L E
1
R
I
B
October 2, 2023 4

5. Base
• Lower end or Base is bounded in front by
the anterior axillary fold formed by
pectoralis major muscle
• Behind by posterior axillary fold formed by
the tendons of latissimus dorsi and teres
major muscles
• Medially by the chest wall
October 2, 2023 5

6. Anterior wall
1. Pectoralis major
2. Pectoralis minor
3. Subclavius muscles
4. Clavipectoral fascia
October 2, 2023 6

7. Posterior wall: By the subscapularis, Latissimus
dorsi and teres major muscles
October 2, 2023 7

8. Walls of The Axilla
• Medial wall:
By the upper 4 or 5 ribs and intercostal
spaces covered by serratus anterior
muscle
• Lateral wall:
By the coracobrachialis and biceps
muscles in the bicipital groove of humerus
October 2, 2023 8

9. Base
The Base of axilla is formed by the skin
stretching between the anterior and
posterior walls
October 2, 2023 9

10. Clavipectoral Fascia
• It is a strong sheet of connective tissue
• Split above to enclose the subclavius
muscle and is attached to the clavicle
• Below it splits to enclose the pectoralis
minor muscle
• Then continues downward as the
suspensory ligament of the axilla
• Then joins the fascial floor of armpit
October 2, 2023 10

11. Contents of The
Axilla
 Cords and branches
of the brachial
plexus
 Axillary artery and
its branches.
 Axillary vein and its
tributaries.
 Axillary lymph nodes.
 Axillary lymphatic
vessels
 Axillary fat.
 Loose connective
tissue.
The neurovascular bundle is enclosed in connective tissue
sheath, called ‘axillary sheath’
Axillary a. & v.
Brachial
plexus
October 2, 2023 11

12. October 2, 2023 12

13. Axillary Artery
• Is a continuation of subclavian artery
• Begins at the lateral border of the 1st rib
• Ends at the lower border of teres major
• It continues as the brachial artery
• Closely related to brachial plexus cords
• Enclosed with them in the axillary sheath
• Axillary sheath is continuous with the
prevertebral fascia
• Pectoralis minor divides it into 3 parts
October 2, 2023 13

14. 1st Part of Axillary Artery
• Extends from the lateral border of the 1st
rib to the upper border of pectoralis minor
October 2, 2023 14

15. October 2, 2023 15

16. Relation
• Anterior: Pectoralis major, covering fascia,
skin, cephalic vein
• Posterior: Long thoracic nerve
• Lateral: Three cords of brachial plexus
• Medial: Axillary vein
October 2, 2023 16

17. 2nd Part of Axillary Artery
• Lies behind the pectoralis minor muscle
October 2, 2023 17

18. Relation
• Anterior: Pectoralis minor and major,
covering fascia and skin
• Posterior: Posterior cord of brachial plexus
• Lateral: Lateral cord of brachial plexus
• Medial: medial cord of brachial plexus and
axillary vein
October 2, 2023 18

19. 3rd Part of Axillary Artery
• Extends from lower border of pectoralis
minor to the lower border of teres major
October 2, 2023 19

20. Relation
• Anterior: Pectoralis major, medial root of
the median nerve
• Posterior: subscapularis, latissimus dorsi
and teres major
• Lateral: Coracobrachialis, biceps, humerus
• Medial: Ulnar nerve, axillary vein, medial
cutaneous nerve of the arm
October 2, 2023 20

21. Branches
• Branches of axillary artery supply the
thoracic wall and the shoulder region
• 1st Part: Highest thoracic artery
• 2nd Part: Thoracoacromial and lateral
thoracic arteries
• 3rd Part: Subscapular artery, anterior and
posterior circumflex humeral arteries
October 2, 2023 21

22. October 2, 2023 22

23. The nerves entering the upper limb
provide the following important functions:
Sensory innervation to skin & deep structures (e.g. joints)
Motor innervation to the muscles
Influence over the diameters of the blood vessels by the
sympathetic vasomotor nerves
Sympathetic secretomotor supply to the sweat glands.
October 2, 2023 23

24. At the root of the neck, the nerves form
Brachial plexus
Nerve fibers derived from different segments of the spinal
cord arranged and distributed efficiently in various parts of
the upper limb.
October 2, 2023 24

25. Most nerves in the upper limb arise from the brachial
plexus, a major nerve network supplying the upper limb; it
begins in the neck and extends into the axilla.
Almost
all branches
of the brachial plexus
arise in the axilla
(after the plexus
has crossed the 1st rib).
October 2, 2023 25

26. The brachial plexus is formed by:
union of the anterior rami of the
last 4 cervical (C5-C8) & first thoracic (T1) nerves
which constitute the roots of the brachial plexus.
Originates in the neck, passes laterally and inferiorly over
rib I, and enters the axilla.
October 2, 2023 26

27. The parts of the brachial plexus, from medial to lateral, are
roots, trunks, divisions, and cords.
All major nerves that innervate the upper limb originate
from the brachial plexus, mostly from the cords.
October 2, 2023 27

28. ROOTS
Anterior rami of C5 to C8, and most of T1.
The roots & trunks enter the the neck by passing between
the anterior scalene and middle scalene muscles.
Close to their origin, the roots receive gray rami
communicantes from the sympathetic trunk.
These carry postganglionic sympathetic fibers onto the roots for
distribution to the periphery.
October 2, 2023 28

29. .
October 2, 2023 29

30. TRUNKS
In the inferior part of the neck, the roots of the brachial
plexus unite to form three trunks:
Superior trunk formed by union of C5 & C6 roots
Middle trunk a continuation of C7 root
Inferior trunk formed by the union of C8 & T1 roots
The inferior trunk lies on rib I posterior to the subclavian artery; the middle and
superior trunks are more superior in position.
October 2, 2023 30

31. DIVISIONS
Each trunk divides into:
anterior & posterior divisions as the plexus passes
through the cervicoaxillary canal posterior to the clavicle.
Anterior divisions of the trunks
supply anterior (flexor) compartments of the upper limb
Posterior divisions of the trunks
supply posterior (extensor) compartments.
No peripheral nerves originate directly from the divisions of the brachial plexus.
October 2, 2023 31

32. October 2, 2023 32

34. CORDS
The three cords of the brachial plexus originate from the
divisions and are related to the second part of the
axillary artery.
October 2, 2023 34

35. Proximal posterior to the subclavian artery in the neck
More distal regions surround the axillary artery
The roots of the
plexus usually
pass through
the gap between
anterior &
middle scalene
muscles.
October 2, 2023 35

36. Lateral cord
Union of anterior divisions of upper & middle trunks
(C5-C7)
Medial cord
Continuation of anterior division of inferior trunk
(C8-T1)
Posterior cord
Union of all three posterior divisions
(C5 to T1)
October 2, 2023 36

37. Branches
Branches of the roots
Dorsal scapular nerve (C5 root of the brachial plexus)
innervates rhomboid major and minor muscles
Long thoracic nerve (anterior rami of C5 to C7)
innervates serratus anterior muscle
October 2, 2023 37

38. Branches of the trunks
The only branches from the trunks of the brachial plexus
are 2 nerves ;originate from the superior trunk.
Suprascapular nerve (C5 & C6)
innervates supraspinatus &
infraspinatus muscles
The nerve to subclavius muscle (C5 & C6)
innervates subclavius muscle
October 2, 2023 38

39. October 2, 2023 39

40. Branches of the lateral cord
Lateral pectoral nerve pectoralis major muscle
October 2, 2023 40

41. October 2, 2023 41

42. Branches of the lateral
cord
Musculocutaneous nerve
Coracobrachialis
Biceps brachii
Brachialis
All 3 flexor muscles @ anterior compartment of the arm
Terminates as lateral cutaneous nerve of forearm.
October 2, 2023 42

43. Branches of the lateral cord
Lateral root of median nerve
 Largest terminal branch of the lateral cord
 Passes medially to join a similar branch from the
medial cord to form the median nerve.
1. Lateral cord
2. Posterior cord
3. Medial cord
4. Lateral root of median nerve
5. Medial root of median nerve
6. Radial nerve
7. Ulnar nerve
8. Median nerve
October 2, 2023 43

44. October 2, 2023 44

45. October 2, 2023 45

46. Branches of the medial cord
1) Medial pectoral nerve
pectoralis major & minor
2) Medial cutaneous nerve of arm
(medial brachial cutaneous nerve)
medial 1/3 of distal arm
3) Medial cutaneous nerve of forearm
(medial antebrachial cutaneous nerve)
medial surface of the forearm down to the wrist
4) Ulnar nerve
5) Median nerve
October 2, 2023 46

47. Flexor carpi ulnaris muscle & medial half of the flexor
digitorum profundus muscle
All intrinsic muscles of the hand (except for the three
thenar muscles and the two lateral lumbrical muscles)
Skin over the palmar surface of the little finger, medial
half of the ring finger, and associated palm and wrist,
and the skin over the dorsal surface of the medial part
of the hand
October 2, 2023 47

48. October 2, 2023 48

49. Most of the muscles in the anterior compartment of the
forearm
(except for the flexor carpi ulnaris muscle and the medial half of the
flexor digitorum profundus muscle)
In the hand
Three thenar muscles associated with the thumb
Two lateral lumbrical muscles associated with movement
of the index and middle fingers
Skin over the palmar surface of the lateral three and one-
half digits and over the lateral side of the palm and
middle of the wrist.
October 2, 2023 49

50. October 2, 2023 50

51. Musculocutaneous nerve, lateral
root of the median nerve,
median nerve, medial root of the
median nerve, ulnar nerve form
an M over the third part of the
axillary artery.
This feature, together with penetration of the
coracobrachialis muscle by the musculocutaneous
nerve, can be used to identify components of the
brachial plexus in the axilla
October 2, 2023 51

52. Branches of the posterior cord
1) Superior subscapular nerve subscapularis muscle
2) Thoracodorsal nerve latissimus dorsi
3) Inferior subscapular nerve subscapularis & teres major
4) Axillary nerve deltoid and teres minor
5) Radial nerve
All these nerves except the radial nerve innervate muscles
associated with the posterior wall of the axilla; the radial
nerve passes into the arm and forearm.
October 2, 2023 52

53. October 2, 2023 53

54. October 2, 2023 54

55. All muscles
in the posterior compartments of the arm & forearm
Skin on the
Posterior aspect of the arm and forearm
Lower lateral surface of the arm
Dorsal lateral surface of the hand
October 2, 2023 55

56. October 2, 2023 56