Which is the largest system in the body?

The integumentary system is considered the largest system in the body because it encompasses the skin along with its associated structures such as hair, nails, and glands. The skin itself is the body's largest organ, serving as a protective barrier that regulates temperature, provides sensory information, and plays a crucial role in various physiological processes. With a total area of around 18 square feet in an average adult, the integumentary system covers and protects the entire body, making it the most extensive system in terms of surface area.

Other systems like the muscular, nervous, and endocrine systems are vital for movement, signaling, and hormonal regulation, respectively, but they do not have the same expansive coverage or surface area as the integumentary system. While they perform essential functions individually, the scope and size of the integumentary system fundamentally make it the largest system in the body.