Human evolution is often told as a tidy story of adaptation, yet some of our most familiar body parts still defy ...

Your sympathetic nervous system is one of the branches of your autonomic nervous system. It controls functions under unconscious control related to “fight or flight.” Your nervous system plays a ...

An organ is a group of tissues that work together to perform a specific task in the body, such as digesting nutrients or producing chemical messengers that enable brain cells to communicate. Although ...

The integumentary system is the physical system that forms the barrier between the external environment and the internal systems of the body. In humans, this system consists of skin, hair, nails, and ...