armpits

The armpit, medically called the axilla, is a shallow underarm region that serves as a passage and contact area for the upper limb and chest. It is formed by skin and underlying tissues, containing fat, hair follicles, sebaceous glands, and sweat glands, as well as nerves and blood vessels. The axilla also houses a group of lymph nodes that participate in immune defense and drainage of the upper limb and chest wall.

The skin of the armpit is often hairier and humid, creating a microenvironment that supports sweat production and bacterial activity. Two main types of sweat glands are present: eccrine glands, which regulate temperature through watery sweat, and apocrine glands, which secrete thicker fluid linked to the development of body odor after bacterial breakdown. Apocrine glands are more active after puberty and tend to be concentrated in this region.

Lymphatic drainage from the armpit involves several axillary lymph node groups, which receive lymph from the arm, chest, and breast. These nodes are clinically important for infection tracking and breast cancer staging, as cancer cells can spread through the lymphatic system to these nodes.

Variability exists in armpit hair density, skin sensitivity, and odor, influenced by hormonal status, age, genetics, and hygiene practices. Common management topics include cleansing, deodorants or antiperspirants, and addressing irritation or infections such as folliculitis or hidradenitis suppurativa. Overall, the armpit is a functionally and clinically significant region due to its roles in thermoregulation, scent, and lymphatic drainage.