nutrients are a kind of simple substance & food contains nutrients for living things ->  food contains simple substances in the form of nutrients  food contains simple substances in the form of nutrients & the breaking down of food into simple substances occurs in the digestive system ->  the digestive system breaks down food into nutrients for the body  food is a kind of substance & digestion is when food is absorbed into the blood stream ->  food is a kind of substance that is absorbed into the blood stream  food is a kind of substance that is absorbed into the blood stream & blood is a vehicle for carrying substances ->  blood is a vehicle for carrying food  blood is a vehicle for carrying food & the circulatory system transports blood throughout the body ->  the circulatory system carries food from the digestive systems throughout the body  the digestive system breaks down food into nutrients for the body & the circulatory system carries food from the digestive systems throughout the body ->  the digestive system and the circulatory system help to break down food and carry it throughout the body  the digestive system and the circulatory system help to break down food and carry it throughout the body & cells are a part of the body -> the digestive system and the circulatory system help to break down food and carry it to the body's cells