The primary function of sweat glands is to regulate body temperature through the process of thermoregulation. When the body's internal temperature rises, sweat glands produce sweat, which is primarily composed of water and some salts. As sweat evaporates from the skin surface, it cools the body down. Additionally, sweating plays a minor role in excreting waste products, such as urea and ammonia. Humans have two main types of sweat glands: eccrine glands, which are distributed widely across the body and respond to heat, and apocrine glands, which are concentrated in areas like the armpits and become active during stress or hormonal changes.