Gross anatomy of Axilla : Contents , Boundaries : High-yield Usmle step 1

Summary

The axilla, or armpit, is a complex anatomical region located between the upper arm and the lateral thoracic wall. It serves as a passageway for vital structures, including vessels, nerves, and lymph nodes. The axilla is surrounded by key muscles and structures that form its boundaries. This region plays a crucial role in lymphatic drainage, especially for the breast and upper limb. Clinical concerns such as axillary abscesses and cancer can involve the axillary nodes, highlighting the importance of palpation and surgical care, particularly in cases of breast carcinoma or infections.

Takeaways

• 😀 The axilla (armpit) is a space between the upper arm and the lateral thoracic wall, typically filled with fat.
• 😀 The apex of the axilla, also called the axillary canal, is a triangular passage that connects the neck to the axilla.
• 😀 The boundaries of the axillary apex are: anteriorly the clavicle, posteriorly the scapula, and medially the first rib.
• 😀 Key structures passing through the axilla include the axillary vessels, brachial plexus cords, long thoracic nerve, and subclavian lymph trunk.
• 😀 The base of the axilla is formed by the skin and axillary fascia, and is bounded by the anterior and posterior axillary folds.
• 😀 The anterior axillary fold is formed by the lower border of the pectoralis major muscle, while the posterior fold is formed by the latissimus dorsi and teres major muscles.
• 😀 The axillary walls consist of the anterior wall (pectoralis major, minor, and associated fascia), posterior wall (subscapularis, latissimus dorsi, and teres major), medial wall (upper ribs and serratus anterior), and lateral wall (intertubercular sulcus and biceps muscles).
• 😀 The axilla contains important structures such as the axillary artery, axillary vein, brachial plexus, axillary lymph nodes, and fat.
• 😀 Axillary lymph nodes are divided into five groups: anterior (pectoral), posterior (subscapular), lateral, central, and apical, which drain lymph from the breast, upper limb, and trunk.
• 😀 Clinical conditions like axillary abscesses, caused by infection of the axillary lymph nodes, may lead to pain and pus formation, requiring surgical drainage through an incision at the base of the axilla.

Q & A

What is the axilla, and what is its anatomical significance?

The axilla, also known as the armpit, is the space between the upper part of the arm and the lateral thoracic wall. It serves as a passageway for various important structures, including vessels, nerves, and lymph nodes. Its anatomical boundaries are crucial for understanding the region's function and associated clinical conditions.

What are the boundaries of the apex of the axilla?

The apex of the axilla, also known as the axillary canal, is triangular in shape and serves as a passage between the neck and the axilla. Its boundaries are: anteriorly the clavicle, posteriorly the superior border of the scapula, and medially the outer border of the first rib.

Which structures pass through the apex of the axilla?

The apex of the axilla transmits several important structures, including the axillary vessels, cords of the brachial plexus, the long thoracic nerve, and the subclavian lymph trunk.

What is the role of the base of the axilla?

The base of the axilla is situated at its lower end and is directed downwards. It is formed by the skin and axillary fascia. The base plays a key role in defining the boundaries of the axillary region, and it is associated with clinical procedures such as draining abscesses.

How is the anterior axillary fold formed, and what is its significance?

The anterior axillary fold is formed by the lower border of the pectoralis major muscle. This fold plays a role in the structure of the axilla and can be palpated clinically to assess the region.

What muscles form the posterior axillary fold?

The posterior axillary fold is formed by the latissimus dorsi and teres major tendons. It provides a structural boundary in the posterior aspect of the axilla.

What are the contents of the axilla?

The axilla contains the axillary artery and its branches, the axillary vein and its tributaries, cords of the brachial plexus and their branches, the long thoracic nerve, intercostal brachial nerves, axillary lymph nodes, and axillary fat.

What is the clinical relevance of the axillary lymph nodes?

The axillary lymph nodes are important in the drainage of lymph from the upper limb, breast, and trunk. Malignancy or infections in these areas can lead to enlarged lymph nodes, which may indicate conditions like breast cancer.

What is the axillary tail of Spence, and why is it important?

The axillary tail of Spence is a part of the breast tissue that extends into the axilla. It is significant because malignancy in this region can lead to the enlargement of axillary lymph nodes, which can be mistaken for the spread of cancer.

How does axillary abscess develop, and how is it treated?

An axillary abscess is mainly caused by an infection of the axillary nodes. Pain and swelling occur as the abscess grows. Treatment typically involves draining the abscess through an incision at the base of the axilla, avoiding injury to major vessels.