The axilla is the area under the arm where the upper limb meets the thorax. It contains muscles, blood vessels, nerves, and lymph nodes. The axilla provides passage from the neck, chest, and arm. Structures like the brachial plexus, axillary artery and vein pass through the apex. The axilla is bounded by the pectoralis major muscle anteriorly and the latissimus dorsi muscle posteriorly. Clinically, the axilla is important for diagnosing conditions like thoracic outlet syndrome and performing lymph node biopsies for breast cancer screening and staging.

1. The axilla
Dr M Idris Siddiqui

2. The axilla
•The axilla is the name given to
an area that lies below the
glenohumeral joint, at the
junction of the upper limb and
the thorax.

8. The size and shape of the axilla
• The axilla region varies with arm
abduction.
• It decreases in size most markedly
when the arm is fully abducted – at
this point, the contents of the axilla
are at most risk of injury.

14. Structures passing through apex
• A illar essels
• Cords of Bra hial Ple us
• Lo g thora i Ner es
• L ph Node effere ts

15. •
Base of the axilla
•It is the lower end of the axilla.
•The ase is for ed the ski stret hi g et ee
the anterior and posterior walls.
•Boundaries
•In front by the anterior axillary fold:
• Formed by the lower border of the pectoralis major
muscle,
•Behind by the posterior axillary fold:
• Formed by the tendon of latissimus dorsi and the teres
major muscle,
•Medially by the chest wall

17. •Formed by intertubercular groove of the humerus.
,Clavipectorial fascia
Longer than anterior wall

18. Axilla

20. Anterior wall
Formed of:
• Cla i le
• Pe toralis ajor & i or
• Su la ius
• Cla ipe toral fas ia
• Suspe sor liga e t of a illa

22. Posterior wall

25. Contents of the axilla
• Muscles
•Axillary artery
•Axillary vein
•Brachial plexus
•Axillary lymph nodes

26. Contents
• The main, and clinically important contents of the axilla region
include muscles, nerves, vasculature and lymphatics:
• Biceps brachii and coracobrachialis – These muscle tendons move
through the axilla, where they attach to the coracoid process of the
scapula.
• Brachial plexus – A collection of spinal nerves that form the
peripheral nerves of the upper limb.
• Axillary artery – It is commonly referred as having three parts, one
medial to the pectoralis minor, one posterior to pectoralis minor, and
one lateral to pectoralis minor. The medial and posterior parts travel
in the axilla.
• Axillary vein – The main vein draining the upper limb, its two largest
tributaries are the cephalic and basilic veins.
• Axillary Lymph nodes

27. The axilla provides a passageway
(1) superiorly via the cervicoaxillary canal to (or from) the
root of the neck,
(2) anteriorly via the clavipectoral triangle to the pectoral
region.
• It is bounded by the pectoralis major, deltoid, and clavicle.
• The cephalic vein enters the axilla via this triangle, while the medial and lateral
pectoral nerves leave.
(3) inferiorly and laterally into the limb itself,
(4) posteriorly via the quadrangular space to the scapular
region, and
(5) inferiorly and medially along the thoracic wall to the
inferiorly placed axioappendicular muscles (serratus
anterior and latissimus dorsi).

29. Clinical Relevance
• Thoracic Outlet Syndrome
• The apex of the axilla region is an opening between the clavicle,
first rib and the scapula. In this apex, the vessels and nerves may
become compressed between the bones – this is called thoracic
outlet syndrome(TOS).
• Common causes of TOS are trauma (e.g fractured clavicle)
and repetitive actions (seen commonly in occupations that require
lifting of the arms) It often presents with pain in the affected limb,
(where the pain is depends on what nerves are affected), tingling,
muscle weakness and discolouration.
• Lymph Node Biopsy
• Approximately 75% of lymph from the breast drains into the axilla
lymph nodes, so can be biopsied if breast cancer is suspected. If
breast cancer is confirmed, the axillary nodes may need to be
removed to prevent the cancer spreading. This is known as axillary
clearance. During this procedure, the long thoracic nerve may
become damaged, resulting in winged scapula.