What is the largest body system in humans?

The integumentary system is the largest body system in humans because it includes the skin, hair, nails, and associated glands. The skin alone is the largest organ of the body, covering the entire exterior surface and playing a crucial role in protecting underlying tissues, regulating temperature, and providing sensory information.

This system serves as a barrier against pathogens and helps prevent fluid loss, while also being involved in immune response and vitamin D synthesis. The extensive surface area of the skin and its complex structure of multiple layers also contribute to its classification as the largest system in the body.

While the nervous, digestive, and musculoskeletal systems are vital for various bodily functions and also quite extensive, they do not encompass as much surface area or volume as the integumentary system.