The Integumentary system, or skin, is our largest organ and protects the body by providing a barrier against infections, dehydration, and sun damage. It regulates temperature, stores water and nutrients, and contains sensory receptors. The skin accounts for 12-15% of body weight and covers 1.5 square meters, distinguishing the body from the external environment while enabling respiration in some aquatic organisms. It has many protective, regulatory, and sensory functions vital for health.