 Respiratory basics. When you breathe, what happens to the air that goes in before it comes back out again? The process is called respiration and the first step is ventilation, air in and air out. When you breathe in, air travels past your nasal cavity, barnacles, larynx, trachea, and bronchi to the many tiny air sacs of the lungs called alveoli. Step two, external respiration is the air exchange between the lungs and the blood. Some of the air you just inhaled from the atmosphere and that is in the alveoli of your lungs will now enter your bloodstream. The oxygen in the air you just inhaled is more concentrated in your alveoli that is in the blood vessels that come into the lungs. Because of this, the oxygen will leave the alveoli of your lungs and enter your blood stream. There is a high level of carbon dioxide in your blood when it enters the lungs so that will leave the vessels and enter the alveolus of the lungs. This CO2 will leave the body when you exhale. What happens to the oxygen? Step three, gas transport. Oxygen is transported by the hemoglobin in your red blood cells while carbon dioxide is primarily transported as a bicarbonate ion. This process is known as gas transport. The process brings the oxygen from your lungs to the cells of your body and returning CO2 from the cells to your lungs to be exhaled and eliminated from your body. After leaving the lungs, the oxygen diffuses from the hemoglobin in the red blood cells to the systemic tissue cells. The carbon dioxide that is generated by the cells diffuses into the bloodstream and is transported back to the lungs. Gas exchange occurring between the blood and systemic tissue cells is known as internal respiration and that is step four. The process known as internal respiration and those are the respiratory basics.