Enumerate the boundaries, contents of axilla, name the various branches of axillary artery

(i)                 THE AXILLA

 The axilla is the space between upper part of medial side of arm and lateral side of thorax. Shape is pyramidal

Boundaries The walls are anterior, posterior, medial and lateral. It has an apex and a base. a. The anterior wall is formed by Pectoralis major Clavipectoral fascia Pectoralis minor b. The posterior wall is formed by‐ Subscapularis Latissimus dorsi Teres major c. The medial wall is formed by Serratus anterior covering upper part of lateral thoracic wall. d. The lateral wall is narrow and formed by Shaft of humerus Coracobrachialis

Short head of biceps brachii

The apex is triangular and directed upwards and medially towards root of neck. It is bounded by Clavicle anteriorly First rib medially Upper border of scapula posteriorly The base of axilla is formed by axillary fascia. Contents of the axilla are:

 a. The axillary artery and its branches

 b. The axillary vein and its tributaries

 c. The three cords of brachial plexus and their branches.

 d. The axillary lymph nodes

e. Fibrofatty tissue

f. The axillary tail of Spence of mammary gland in females.

THE AXILLARY ARTERY

The axillary artery is the main arterial trunk of the upper extremity.∙

 Beginning

The axillary artery begins at the outer border of first rib as continuation of third part of subclavian artery.

Course

 The artery passes laterally and downwards.

 a. First part extends from outer border of first rib to medial border of pectoralis minor.

 b. Second part is the short segment of artery that lies behind pectoralis minor.

 c. Third part is the longest part that extends from lateral border of pectoralis minor to lower border of teres major.

Branches

The artery gives six branches.

From first part:

one branch

 1.The superior thoracic artery is a small branch supplying first intercostal space.

From second part:

two branches

 2. The thoracoacromial artery pierces clavipectoral fascia and divides into four branches. a. The deltoid branch lies in deltopectoral groove.

b. The clavicular branch supplies sternoclavicular joint and subclavius muscle.

c. The pectoral branch for the pectoral muscles.

d. The acromion branch takes part in anastomosis over acromion process.

 3. The lateral thoracic artery runs along the lateral border of pectoralis minor

In females, it is large and supplies the mammary gland.

From third part:

three branches

 4. The anterior circumflex humeral curves around the surgical neck of humerus from front.

 5. The posterior circumflex humeral is a larger branch that accompanies axillary nerve through quadrangular space.

 6. The subscapular artery is large artery that follows lateral border of scapula.