Corpus: Axilla
Synonym: armpit
1. Definition
The axilla is a pyramid-shaped anatomical space located between the lateral chest wall and the medial humerus.
In everyday language, the term "axilla" often refers to the fold of skin between the chest wall and upper arm, which becomes hairy in adults.
2. Borders
The apex of the axilla points cranially and is bordered by the lower part of the first rib, the upper edge of the shoulder blade (scapula), and the collarbone (clavicle). The base of the axilla faces caudally and is broad where it meets the chest wall, narrowing as it tapers toward the upper arm. The base is formed by the skin and a thick layer of connective tissue called the axillary fascia.
The anterior wall of the axilla is formed by the pectoralis major muscle and the pectoralis minor muscle. The space between the pectoralis minor muscle and the clavicle is spanned by the clavipectoral fascia.
The posterior wall of the axilla extends lower than the anterior wall. It is made up of the subscapular muscle at the top and the teres major and latissimus dorsi muscles at the bottom.
The medial border of the axilla is formed by the first four ribs with the intercostal muscles between them and part of the serratus anterior muscle.
On the lateral side, the anterior and posterior walls converge to form a narrow surface that is formed by the humerus, the coracobrachialis muscle and the biceps brachii muscle.
3. Structures
3.1. Vessels
- Axillary artery and its branches:
- Axillary vein
3.2. Nerves
- Brachial plexus and its branches, including:
- intercostal nerves
3.3. Other
- Axillary lymph nodes
- Adipose tissue