Stop breathing for 10 minutes and what happens? You won’t be alive to answer that question. You see, have you ever thought about what happens when you inhale (take air in) and exhale (take air out)? As almost all of the things that occur within our body I’m pretty sure you haven’t, unless you’re some sort of scientist. Respiration is perhaps the most essential system for the preservation of our lives and we’re barely even conscious of it when it takes place.

A practical definition of respiration is “the process of ventilating the lungs through an alternation of inhaling and exhaling air”. We inhale oxygen and exchange it for carbon dioxide which we exhale. For certain, many reading this essay will know that the nose, the lungs, the ribs, and the brain are part of breathing, but other features include the trachea, bronchi, bronchioles, alveoli, and diaphragm. Let’s analyze in depth our respiration process.

The lungs are divided and subdivided into numerous compartments. They are a sponge-like organ which is interpenetrated with blood vessels and capillaries. At the instant you allow air inside your body, this one will pass through the trachea (part of the throat that leads to lungs), which is behind the esophagus (part of the throat that leads to stomach). The trachea separates into two bronchi which are too branched into bronchioles. Then, the bronchioles are divided into even smaller branches, ultimately ending in the alveoli aligned with capillaries where gas exchange occurs.

Oxygen-rich air we breathe is dissolved in the moist lining of the alveoli. The blood in the capillaries is carrying much carbon dioxide and very little oxygen. This difference in partial pressure causes highly concentrated oxygen in the lungs to diffuse into the blood in the capillaries and carbon dioxide to diffuse out of the blood into the alveoli to be exhaled. With this exchange process, more oxygen is able to be inhaled enabling us to prevail in the continuous living of our lives. When the air pressure is high inside the lungs, the air from the lungs flows out. When the air pressure is low inside, then air flows into the lungs.

Diffusion is the proper name for this basic process of trade. The word diffusion is derived from the Latin word, “diffundere”, which means “to spread out”. If a substance is “spreading out”, it is moving from an area of high concentration to an area of low concentration. Carbon dioxide in the capillaries “spreads out” and allows a higher concentration of oxygen to enter and expel the CO2. Both oxygen and carbon dioxide are transported around the body in the blood through arteries, veins and capillaries. They bind to hemoglobin in red blood cells, although oxygen does so more effectively.

Inside our thoracic cavity are the lungs approximately contained by the rib cage. A muscular partition known as the diaphragm forms the bottom wall of the thoracic cavity. When we respire this muscle contracts, the intercostal muscles (between the ribs) pull the ribs up, pull the sternum out enlarging the cavity and reducing air pressure in the lungs. The air containing higher pressure than the alveoli rushes inside our lungs and the pressure in the air and alveoli are relatively equalized. However, the concentration of oxygen is greater in the newly arrived air than that one of the alveoli. After this happens, the oxygen and carbon dioxide will diffuse as previously described within the capillaries.

In a nutshell this is what happens when we breathe. Inhalation is initiated by the diaphragm and intercostal muscles expanding the lungs and allowing a high pressure of air to enter the lungs and oxygen to enter the alveoli to exchange carbon dioxide in the blood through the capillaries. Carbon dioxide is expelled through exhalation to begin the cycle all over again. All of this in a matter of seconds.


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