What major function does the integumentary system serve?

The integumentary system primarily serves the function of protecting the body against environmental hazards. This system encompasses the skin, hair, nails, and associated glands. Its primary role is to act as a barrier, shielding underlying tissues and organs from pathogens, mechanical damage, chemical exposure, and dehydration. By maintaining this protective barrier, the integumentary system helps to prevent infections and harmful substances from entering the body, which is crucial for overall health.

Additionally, while regulating body temperature is an important function of the integumentary system—through mechanisms like sweat production and the dilation or constriction of blood vessels—it is part of a broader array of roles that the system fulfills. However, the foundational aspect of protection remains the most significant and defining characteristic of the integumentary system, making it the correct answer.