Here's why:

* Integumentary system: This system includes the skin, hair, nails, and glands. The skin itself is a large, complex membrane that acts as a barrier, protects against infection, regulates temperature, and performs other vital functions.

* Membrane: A membrane is a thin layer of tissue that covers a surface or lines a cavity.

* Organ system: A group of organs that work together to perform a specific function.

Therefore, the integumentary system meets the criteria for both a membrane and an organ system.