Final answer:
The circulatory, nervous, and digestive systems are examples of organ systems, which consist of groups of organs working together to perform vital bodily functions.
Step-by-step explanation:
The circulatory system, the nervous system, and the digestive system are all examples of organ systems within the human body. Organ systems are groups of organs that work together to perform complex functions that are vital for the organism's survival. For instance, the nervous system includes the brain, spinal cord, and nerves, coordinating bodily functions and responses to stimuli. The circulatory system, consisting of the heart, blood vessels, and blood, is responsible for transporting nutrients, oxygen, hormones, and wastes throughout the body. The digestive system, encompassing organs like the mouth, stomach, intestines, and liver, breaks down food into nutrients that can be absorbed and utilized by the body.