Organ systems are groups of organs that work together to perform specific functions in the body. Each system has a unique role, such as the circulatory system, which transports blood and nutrients, or the digestive system, which breaks down food for energy. There are several organ systems in the human body, including the respiratory system, which enables breathing, and the nervous system, which controls body activities through signals. These systems interact and depend on each other to maintain overall health and function, ensuring that the body operates efficiently.