The cardiovascular system includes the heart and the blood vessels, and the respiratory system contains those organs which are responsible for carrying oxygen from the air to the blood stream and expelling the waste product of carbon dioxide. Blood is that sticky, red fluid that circulates throughout our bodies in veins and arteries. The heart pumps oxygen into the blood and collects carbon dioxide from it to be expelled through the lungs. We usually think of respiration as the process of the lungs after air is breathed in through the mouth or nose. The lungs do play a very important role, but every living cell in the body is involved in this process.
Respiration is the act of burning energy from oxygen.
Breathing is an obvious part of the respiratory passages, but these also involve yawning, sneezing, coughing, hiccups, the power of speech, and the sense of smell. These systems' tasks include organs which take up space in the face and neck and most of the chest. The cardiovascular and respiratory systems are basic to life and breathing, like the beat of one's heart, is an automatic function which is controlled by the brain. The digestive system is a group of organs that work like wrecking equipment to break down the chemical components of food, through the use of digestive juices, into tiny nutrients which can be absorbed to generate energy for the body. This system also builds and replaces cells and tissues, which are constantly dying.