Axilla in the context of "Armpit hair"

In human anatomy, the arm refers to the upper limb in common usage, although academically the term specifically means the upper arm between the glenohumeral joint (shoulder joint) and the elbow joint. The distal part of the upper arm between the elbow and the radiocarpal joint (wrist joint) is known as the forearm or "lower" arm, and the extremity beyond the wrist is the hand.

By anatomical definitions, the bones, ligaments and skeletal muscles of the shoulder girdle, as well as the axilla between them, are considered parts of the upper limb, and thus also components of the arm. The Latin term brachium, which serves as a root word for naming many anatomical structures, may refer to either the upper arm as a whole or to the upper arm on its own.

The Improved Outer Tactical Vest (IOTV) is an enhanced version of, and a replacement for, the older Outer Tactical Vest (OTV) component of the Interceptor multi-threat body armor system, as fielded by the United States Army beginning in the mid-2000s. The IOTV is compatible with the Deltoid and Axillary Protector System (DAPS) components, ESAPI (Enhanced Small Arms Protective Insert), Enhanced Side Ballistic Inserts (ESBI), as well as the OTV's groin protector. A flame-resistant standalone shirt, the Army Combat Shirt (ACS), was designed in the late 2000s specifically for use with the IOTV.

The OTV design was considered insufficient and lacking in certain areas, which led to the IOTV's development and fielding beginning in 2007. The IOTV is currently produced by Point Blank Body Armor, BAE Systems, KDH Defense Systems, Protective Products Enterprises, UNICOR and Creative Apparel Associates. The IOTV first saw action in combat with U.S. Army ground combat units in from mid-2007 onward and currently remains the standard body armor type used by regular U.S. Army ground combat units overseas, although the new Modular Scalable Vest is set to replace it in the coming years.

Sweat glands, also known as sudoriferous or sudoriparous glands, from Latin sudor 'sweat', are small tubular structures of the skin that produce sweat. Sweat glands are a type of exocrine gland, which are glands that produce and secrete substances onto an epithelial surface by way of a duct. There are two main types of sweat glands that differ in their structure, function, secretory product, mechanism of excretion, anatomic distribution, and distribution across species:

• Eccrine sweat glands are distributed almost all over the human body, in varying densities, with the highest density in palms and soles, then on the head, but much less on the trunk and the extremities. Their water-based secretion represents a primary form of cooling in humans.
• Apocrine sweat glands are mostly limited to the axillae (armpits) and perineal area in humans. They are not significant for cooling in humans, but are the sole effective sweat glands in hoofed animals, such as the camels, donkeys, horses, and cattle.

Ceruminous glands (which produce ear wax), mammary glands (which produce milk), and ciliary glands in the eyelids are modified apocrine sweat glands.