organs systems Describe the purpose or function of each organ system. Circulatory System: Transports nutrients, gases and waste in the body. Nervous system: Detects and responds to changes in the environment. Endocrine system: Creates and releases hormones to send signals to cells in the body. Excretory system: Removes waste from the body as urine. Digestive system: Breaks down food to energy and nutrients Respiratory system: gases between the blood and the atmosphere. Lymphatic system: Defends the body against infections (immune system) Reproductive system Ensures the survival of the species by producing offspring Muscular system: Produces voluntary movement. Skeleton system: Protects internal organ. Integumentary system: Guards against ultraviolet light