Which body system includes the skin, hair, and nails and provides a protective barrier?

• A. Nervous system
• B. Circulatory system
• C. Integumentary system
• D. Respiratory system

Answer: (C)

The key idea is recognizing which body system is built to protect the body from the outside world. The integumentary system includes the skin, hair, and nails, and its main role is to form a protective barrier that guards against injury, dehydration, and pathogens. The skin serves as a waterproof shield and, with its layers, helps regulate temperature, preserve moisture, and sense the environment; hair and nails contribute additional protective and barrier functions. This system also houses immune components and aids in vitamin D synthesis when exposed to sunlight. In contrast, the nervous system focuses on communication and control, the circulatory system moves blood throughout the body, and the respiratory system handles gas exchange, so they don’t fit the description as directly as the integumentary system.