The primary function of the skin in humans is to act as a protective barrier. It shields underlying tissues from pathogens, physical injury, and harmful substances, while also helping to regulate temperature and maintain hydration. Skin contains sensory receptors that enable the detection of stimuli such as touch, pain, and temperature, which contribute to the body's response to the external environment. Additionally, the skin plays a role in the synthesis of vitamin D and the storage of lipids. Therefore, it is vital for overall health and homeostasis.