Which component is NOT part of the integumentary system?

The integumentary system is primarily composed of the skin along with its associated structures, which include hair, sweat glands, oil glands, and nails. Each of these components plays a critical role in protecting the body, regulating temperature, and providing sensory information.

Muscles, while vital for movement and function in the body, do not belong to the integumentary system. Instead, they are part of the musculoskeletal system, which works with bones to facilitate movement. Therefore, identifying muscles as not part of the integumentary system highlights an understanding of how different systems in the human body are categorized based on their functions and structures.