Axilla Anatomy Overview

Located between the arm and thorax, inferior to the glenohumeral joint.
Serves as a passageway for neurovascular structures from the neck to the arm.
Pyramidal structure, crucial for containing lymph nodes and neurovascular bundles.
Significant in medical concerns like breast cancer.

Apex: Formed by the 1st rib, clavicle, and superior border of the scapula.
Base: Comprises skin and axillary fascia (armpit).
Anterior Border: Pectoralis major and pectoralis minor muscles.
Posterior Border: Includes scapula, subscapularis, teres major, and latissimus dorsi.
Medial Border: Composed of ribs 1-4 and intercostal muscles, serratus anterior.
Lateral Border: Defined by the humerus.

Lymph Nodes: Axillary lymph nodes drain lymph from the upper limb and portions of the thoracic wall, particularly the breast, and are arranged in five groups.
Drains to supraclavicular nodes for further filtration.

Enclosed in the axillary sheath (a thin fascial layer).
Divided into three parts:
- Part 1: From the lateral border of the 1st rib to the medial border of pectoralis minor with one branch: Superior thoracic artery.
- Part 2: Located posterior to pectoralis minor with two branches: Thoraco-acromial artery (divided into pectoral, clavicular, acromial, and deltoid branches) and lateral thoracic artery (supplies the breast).
- Part 3: From the lateral border of pectoralis minor to the inferior border of teres major, with three branches: Subscapular artery, anterior circumflex humeral artery, and posterior circumflex humeral artery.
Forms anastomoses around the shoulder for alternative blood supply routes.

Transitions to the brachial artery at the inferior border of teres major, marking the site of the brachial pulse.

Continuation of the basilic vein and merges as the subclavian vein at the lateral border of the 1st rib.
Drains both superficial and deep venous networks, including tributaries from the cephalic vein, basilic vein, and median cubital vein.
Variability in shape (H, N, W) at different locations, becoming more consistent at the cubital fossa.

Vital for immune system function, draining lymph from the upper extremity and contributing to overall systemic drainage.
Presence of lymph vessels associated with surrounding veins ensures thorough drainage.

Injuries or ligation of axillary contents can have significant implications for upper limb function and lymphatic drainage, particularly in the context of oncological assessments.