Which term describes the layer of tissue that separates the body from the external environment?

The term that accurately describes the layer of tissue that separates the body from the external environment is the skin. The skin is an organ composed of multiple layers, primarily the epidermis and dermis, and serves as the body's first line of defense against environmental threats such as pathogens, chemicals, and physical injury.

The epidermis is the outermost layer, providing a waterproof barrier and contributing to skin tone, while the dermis lies beneath it, containing connective tissue, hair follicles, sweat glands, and other structures. Together, these layers form the protective covering known as the skin, which is essential for regulating temperature, sensation, and overall body protection.

While the dermis and hypodermis (or subcutaneous layer) play important roles in supporting the skin and connecting it to underlying tissues, they do not encompass the entirety of what distinguishes the skin as a barrier between the body and the external environment. The skin specifically refers to the complete organ system involved in this protective function.