Axilla

 What are the Boundaries and Contents of Axilla?

Axilla is a four-sided pyramidal space situated  between the upper part of the arm and  upper  part of lateral thoracic  wall. Its boundaries are as follows:

Apex: Is directed upwards and medially and is formed by cervicoaxillary  canal via which it communicates with the posterior triangle of neck .
Boundaries of cervicoaxillary canal are:

• Anteriorly: middle third of clavicle.
• Posteriorly: superior border of scapula.
• Medially: outer border of 1st rib.

Base: Is formed by skin, superficial fascia and dome-shaped axillary fascia

Anterior wall is formed by pectoralis major, clavipectoral fascia enclosing pectoralis minor and subclavius muscles.

Posterior wall is formed by subscapulais,teres major and latissimus dorsi.

Medial wall is formed by upper four ribs and intercostal muscles, upper four digitations of serratus anterior.

Lateral wall is formed by upper part of humerus (intertubercular sulcus)  with long head of biceps brachii and short head of biceps brachii and coracobrachialis muscle.

Enumerate the Contents of Axilla.

The contents of axilla are:

1. Axillary artery & its branches
2. Axillary vein & its tributaries
3. Axillary lymph nodes
4. Axillary tail of mammary gland (tail of Spence)
5. Cords of brachial plexus
6. Long thoracic nerve
7. Intercostobrachial nerve
8. Axillary fat & areolar tissue.

What are the various Groups of Axillary Lymph Nodes?

A. There are 5 groups of axillary lymph nodes which are as follows:

1. Anterior/pectoral: Are located along the lower border of the pectoralis minor. They receive lymph  from the lateral quadrants of mammary gland and anterolateral abdominal wall above the level of the umbilicus.
2. Posterior/subscapular: Are located in front of the subscapularis muscle. They receive superficial lymph vessels from the back, till the level of Iliac crests.
3. Lateral: Are located along the medial side of the axillary vein. They receive most of the lymph from the upper limb  except the lateral side of the hand, forearm, and arm  (it drains into infraclavicular lymph nodes).
4. Central: Are located in the center of the axilla. They receive lymph from the above three groups.
5. Apical: Are located at the apex of axilla near the lateral border of the 1st rib. They receive  lymph  from all the other axillary nodes.

Apical nodes drain lymph into subclavian lymph trunk which on the left side drains into thoracic duct and on the right side into the right lymphatic duct. 

Name the Parts and Branches of Axillary Artery.

Branches of axillary artery 

Axillary artery extends from outer border of 1^st rib to the lower border of teres major. It is divided into three parts by pectoralis minor muscle. Branches of the three parts are as follows :

First part ( proximal to pectoralis minor) 

• Superior thoracic artery

Second part (deep to pectoralis minor)

• Thoracoacromial artery
• Lateral thoracic artery

Third part (distal to pectoralis minor)

• Anterior circumflex humeral artery
• Posterior circumflex humeral artery
• Scapular artery

Applied Aspects