What is the Axilla?
The axilla is the junction between the inner part of the upper arm and the shoulder. This part is commonly known as the armpit in which many anatomical structures pass through for support of the upper extremities. The axilla is pyramidal in shape. It has an apex which is directed towards the neck area. The base of this pyramid faces downward toward the body. The apex of the axilla is bordered anteriorly by the collar bone or clavicle, posteriorly by the upper border of our shoulder blades called the scapula, and medially by the first rib. The base meanwhile is bordered by several muscles. On the anterior part, the pectoralis major borders it. On the posterior part, some muscles attached to the shoulder blade act as borders. These muscles include the subscapularis and teres major. The latissimus dorsi with attachments to the ribs and trunk also form part of the posterior border for the base of the axilla. Medially, the base is bordered by the muscles in between the ribs, and laterally, the upper part of the humeral shaft along with the coracobrachialis muscle serve as borders.
Located in the axilla region are lymph nodes, which are important for drainage of lymph from the upper parts of the body including the neck, shoulder, and upper arms or extremities. These lymph nodes are parts of the body’s system to provide immunity from diseases. Another important structure that passes through the axilla is the brachial plexus. This brachial plexus is like a nerve pathway which supplies sensory signals to most parts of the upper arm. If this part is damaged, then one can expect a decrease or absence of normal sensation in the upper arm region. Other structures that pass through the axilla are the axillary artery and veins with their branches, the intercostobrachial nerves, the long thoracic nerve, and the infraclavicular part of the brachial nerve.
The apocrine glands are also located in the axilla. These glands produce sweat under the arm usually at the onset of puberty. It is also at the time of puberty when hair growth is noticed in the axilla. Because of these changes, various personal hygiene activities are modified and adjusted according to the body’s needs.