The organ in the human body that helps regulate body temperature is the skin. The skin plays a critical role in thermoregulation through various mechanisms. It contains sweat glands that secrete sweat, which evaporates to cool the body. Additionally, blood vessels in the skin can dilate or constrict; when they dilate, more blood reaches the surface, releasing heat, while constriction reduces blood flow to retain warmth. The skin also acts as a barrier, providing protection from external elements. By maintaining a stable internal temperature, the skin helps ensure the proper functioning of organs and systems within the body, contributing to overall health and homeostasis.