The primary function of the respiratory system is to supply the blood with oxygen in order for the blood to deliver oxygen to all parts of the body. The word respiration describes two processes. Your respiratory system provides the energy needed by cells of the body. Rib muscles contract to pull ribs up and out. All animals need oxygen to live.
Land animals get oxygen from the air.
Without the oxygen in the air we cannot survive more than a few minutes. Breathing happens automatically, we do not have to even think about it. Although it may seem easier to breathe through the mouth, it is healthier to breathe through the nose. This page compares the respiratory systems of other living things. The Respiratory System Breathing and the ways the body uses oxygen are called respiration.