Which body system regulates body temperature, protects the body from outside toxins, and is composed of three layers?

• A. Integumentary
• B. Skeletal
• C. Muscular
• D. Nervous

Answer: (A)

The integumentary system—the skin and its associated structures—fits this description because it helps regulate body temperature, acts as a protective barrier against toxins and pathogens, and is organized into three layers: the epidermis on the outside, the dermis beneath it, and the hypodermis (subcutaneous tissue) deepest. Temperature regulation happens through sweat production and adjustments in blood flow to the skin, while insulation comes from fat stored in the hypodermis. The epidermis provides the outer protective shield, and the dermis houses glands, hair follicles, and nerve endings, all contributing to protection and sensation. The other systems don’t serve as the primary barrier with a three-layer skin structure and the same temperature-regulation mechanisms.