And the LORD God formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living soul.(Genesis 2:7)
In the human body, the oxygen is absorbed by the blood stream in the lungs, being then transported to the cells where an elaborated change process takes place.
Oxygen plays a vital role in the breathing processes and in the metabolism of the living organisms.
Probably, the only living cells that do not need oxygen are some anaerobic bacteria that obtain energy from other metabolic processes.
The nutrient compounds, inside of the cell, are oxidized through complex enzymatic processes.
This oxidation is the source of energy of most of the animals, mainly of mammals.
The products are carbon dioxide and water (exhaled air has a relative humidity of 100%), which are eliminated by the human body through the lungs.
Appropriate levels of oxygen are vital to support cell respiration. Oxygen plays an important role in the energy metabolism of living organisms.
The living cell is the site of tremendous biochemical activity called metabolism.
This is the process of chemical and physical change which goes on continually in the human body: build-up of new tissue, replacement of old tissue, conversion of food to energy, disposal of waste materials, reproduction - all the activities that we characterize as "life."
Research shows that cells have only a "limited number" of cell divisions possible in a human lifetime.
Studies show that by the time you're 20 most of the cells that make up your body have used up half of the divisions available in their cell lifespan.
By the time you're 40, there are maybe only 30% of your possible cell divisions left. When the cells use up their natural allotted cell divisions, the end is death!
The respiratory system is the group of tissues and organs in your body that enable you to breathe. This system includes your airways, your lungs and the blood vessels and muscles attached to them that work together so you can breathe. The respiratory system's primary function is to supply oxygen to all the parts of your body. It accomplishes this through breathing: inhaling oxygen-rich air and exhaling air filled with carbon dioxide, which is a waste gas.
The respiratory system is made up of airways (your nose, mouth, voice box, windpipe and bronchial tubes) and the lungs and the muscles and blood vessels connected to them.
This is how the respiratory system works: First you breathe air in through your nose and mouth, which wet and warm the air so it won't irritate your lungs. Then the air travels through your voice box, down your windpipe and then though two bronchii (bronchial tubes) into your lungs. Cilia (tiny mucous-covered hairs) in your airways entrap foreign particles and germs to filter the air that you breathe. You then cough or sneeze the particles out of your body.
The diaphragm, abdominal muscles and other muscles help your lungs expand and contract so you can inhale and exhale. When you inhale, the air goes through the bronchii in your lungs to blood vessels that connect to veins and arteries. These veins and arteries carry the blood throughout your body. When you exhale, the carbon dioxide goes out the same way, exiting your body through your nose and mouth. If you can't breathe or can't breathe well, not only will your body not receive enough oxygen to keep it running, but it will also be poisoned by the carbon dioxide that is building up in your blood and has nowhere to go.