Axilla Anatomy

Definition and Location

• The axilla is the armpit or the hollow under the arm, specifically the region between the upper arm and the side of the chest.
• It is a triangular space formed by the thoracic wall, the humerus, and the scapula.

Boundaries

• Medial boundary: formed by the thoracic wall and the medial aspect of the upper arm
• Lateral boundary: formed by the humerus
• Anterior boundary: formed by the pectoralis major muscle
• Posterior boundary: formed by the subscapularis muscle and the teres major muscle
• Apex: formed by the convergence of the medial and lateral boundaries
• Base: formed by the thoracic wall

Contents

• Axillary artery and its branches
• Axillary vein and its tributaries
• Brachial plexus (nerves C5-T1)
• Axillary lymph nodes (20-40 nodes)
• Areolar tissue and fat
• Axillary hair

Functions

• Allows for mobility and flexibility of the shoulder joint
• Provides a pathway for nerves and blood vessels to the upper limb
• Houses lymph nodes that filter lymphatic fluid and aid in the immune response
• Supports the weight of the arm

Clinical Significance

• Axillary lymph node examination is important in cancer diagnosis and staging
• Axillary dissection is a surgical procedure used to remove cancerous lymph nodes
• Axillary nerve damage can result in weakened shoulder abduction and loss of sensation on the lateral arm

Axilla (Armpit) Anatomy

• The axilla is the triangular space between the upper arm and the side of the chest.

Boundaries

• Medial boundary: thoracic wall and medial aspect of the upper arm
• Lateral boundary: humerus
• Anterior boundary: pectoralis major muscle
• Posterior boundary: subscapularis muscle and teres major muscle
• Apex: convergence of medial and lateral boundaries
• Base: thoracic wall

Axilla Contents

• Axillary artery and its branches
• Axillary vein and its tributaries
• Brachial plexus (nerves C5-T1)
• Axillary lymph nodes (20-40 nodes)
• Areolar tissue and fat
• Axillary hair

Functions of the Axilla

• Allows for mobility and flexibility of the shoulder joint
• Provides a pathway for nerves and blood vessels to the upper limb
• Houses lymph nodes that filter lymphatic fluid and aid in the immune response
• Supports the weight of the arm

Clinical Significance

• Axillary lymph node examination is important in cancer diagnosis and staging
• Axillary dissection is a surgical procedure used to remove cancerous lymph nodes
• Axillary nerve damage can result in weakened shoulder abduction and loss of sensation on the lateral arm

Learn about the axilla, also known as the armpit, and its boundaries in the human body. Understand the triangular space formed by the thoracic wall, humerus, and scapula.