The system that covers the external surface of the body and protects deeper tissues is the integumentary system.

This system includes:

* Skin: The largest organ in the body, providing a physical barrier against infection, injury, and dehydration.

* Hair: Provides insulation, protection, and sensory input.

* Nails: Protect fingertips and toes.

* Sweat glands: Regulate body temperature.

* Sebaceous glands: Produce oil to lubricate the skin and hair.

So, the integumentary system is your body's first line of defense against the outside world!