Breathing is the process of inhaling and exhaling air from the lungs. When a person inhales, his lungs expand and pull life-sustaining oxygen into the body. When a person exhales, the lungs contract, and a waste product called carbon dioxide is expelled from the body, notes WebMD.
The human respiratory system contains the organs in the body that allow humans to breathe, including the lungs, blood vessels and airways. These organs work together to supply the body with the oxygen-rich air required for survival. The air humans breathe in supplies oxygen to every part of the body. When a person inhales, the air travels through the voice box, down the windpipe and into the lungs. The air then travels into the blood vessels that connect to the arteries and veins. The veins and arteries carry the oxygen throughout the body to keep the body running efficiently, notes the National Heart, Lung and Blood Institute. Without a steady supply of oxygen, humans cannot survive.
For healthy people, the process of breathing comes naturally and does not require any effort from the body, according to WebMD. However, a person suffering from a respiratory condition or lung disease, such as asthma or emphysema, will often need to use an inhaler, portable oxygen machine or other device that assists with breathing.