The Axilla
The Axilla The axilla, or armpit, is a pyramid-shaped space between the upper part of the arm and the side of the chest. It forms an important passage for nerves, blood, and lymph vessels as they travel from the root of the neck to the upper limb.The Axilla The upper end of the axilla, or apex, is directed into the root of the neck and is bounded in front by the clavicle, behind by the upper border of the scapula, and medially by the outer border of the first rib.
The Axilla The lower end, or base, is bounded in front by the anterior axillary fold (formed by the lower border of the pectoralis major muscle), behind by the posterior axillary fold (formed by the tendon of latissimus dorsi and the teres major muscle), and medially by the chest wall.
Walls of the Axilla
The AxillaWalls of the Axilla:■ Anterior wall: By the pectoralis major, subclavius, andpectoralis minor muscles. The Axilla
Walls of the Axilla:■ Posterior wall: By the subscapularis, latissimus dorsi, and teres major muscles from above down. The Axilla
Walls of the Axilla:■ Medial wall: By the upper four or five ribs and the intercostal spaces covered by the serratus anterior muscle. The Axilla
Walls of the Axilla:■ Lateral wall: By the coracobrachialis and biceps muscles in the bicipital groove of the humerus. The Axilla
Walls of the Axilla: The base is formed by the skin stretching between the anterior and posterior walls.
The Axilla
Key Muscle in the Axilla (Pectoralis Minor): It is a thin triangular muscle that lies beneath the pectoralis major. It arises from the 3rd, 4th, and 5th ribs and runs upward and laterally to be inserted by its apex into the coracoid process of the scapula. It crosses the axillary artery and the brachial plexus of nerves. It is used when describing the axillary artery to divide it into three parts.