Breathing: everyone does it, but how does it work? Most people tend to equate breathing with respiration, assuming they are one and the same, but really the process of respiration is a much longer, more complicated system, of which breathing is just one of its many steps. There are also two different types of respiration: cellular and physiological, the latter of which concerns the process of breathing and the respiratory system.
In this guide, we’ll cover physiological respiration, and touch a bit on cellular respiration and its two types: aerobic and anaerobic. For some more helpful background information, consider this introduction to biology course.
What is Respiration?
There are two types of respiration: cellular and physiological. Before we get into either, you might want to consider this course on medical terminology or this course on the principles of medical language, both of which should make understanding the processes described here much easier.
- Cellular Respiration
The process of converting molecules into energy through oxidization. This is the opposite of photosynthesis, the biochemical process used by plants and some types of bacteria to convert light energy into chemical energy. Learn more about photosynthesis in this guide.
In terms of cellular respiration, there are two types: aerobic and anaerobic. In short, the process of aerobic respiration requires oxygen, while the process of anaerobic respiration does not require oxygen. Learn a bit more about both aerobic and anaerobic respiration in this guide.
- Physiological Respiration
The process involving absorption of oxygen in the air into the cells of an organism, with the output of carbon dioxide back into the environment. It is a cycle between the organisms that breath oxygen and the organisms that breath carbon dioxide.
There are two types of physiological respiration in animals: internal respiration, and external respiration. Internal respiration is the process of cells in the body exchanging gases, while external respiration is the process of respiration that actually takes place within respiratory organs like the lungs. This is the actual exchange of oxygen and carbon dioxide between an organism and its environment, which involves the process of breathing directly.
It’s important to work out and learn proper breathing techniques to maintain a strong cardiovascular and respiratory system. Check out this runner’s guide to great cardio exercises and learn how to stay in shape.
Process of Respiration: Physiological
For humans and other oxygen-breathing vertebrates, the process of respiration takes place within the lungs, driven by a series of mechanics called inhalation and exhalation. These are the biological mechanisms that make up breathing. We breathe in to take in oxygen, and breathe out to expel carbon dioxide! There’s more involved with the process of respiration than just the lungs, though. The entire process uses the nasal cavity, the mouth, the larynx, the trachea, and the bronchial tubes of the lungs as well. Learn more about human anatomy in relation to physiology in this course.
- External Respiration
To breathe in and breathe out, we use our intercostal muscles, the muscle group that lies between our ribs. When we breathe in through the nose or mouth, these intercostal muscles contract, our sternum moves up and out along with our ribs, and our diaphragm flattens. The diaphragm is a sheet of muscle that lies across the bottom of the rib cage, and it is vital for proper respiration. When the diaphragm contracts, this allows the volume in our thoracic cavity to expand, thus reducing pressure and enabling us to draw air into our lungs. With the help of our diaphragm and thoracic cavity, our body creates a literal suction.
Similarly, when we exhale, our intercostal muscles and our diaphragm relax. This causes the volume of the thoracic cavity to decrease and the pressure inside to increase, which expels the air in what is called an exhalation.
- Internal Respiration
What is actually happening inside the body between the inhale and the exhale? That’s where internal respiration comes in. Internal respiration occurs after and during the process of external respiration, and it’s when the gases in the air we’ve drawn into our lungs can be sorted out, the oxygen absorbed in our blood and the carbon dioxide removed.
This happens because our heart is pumping oxygen-low blood through the pulmonary arteries and into the lungs. At the ends of the pulmonary arteries are small blood vessels called capillaries, which wrap like a net around the alveoli. The alveoli is where our bronchial tubes transport the air we inhale. They are the round, clustered, and sac-like tips of the respiratory tree where gas exchange occurs.
Inside the alveoli, the oxygen rich air we’ve inhaled is pumped into the red blood cells located in the surrounding capillaries, enriching the blood with much needed oxygen. In exchange, the red blood cells expel the carbon dioxide they’re carrying into the alveoli.
Carbon dioxide is a waste product created through the process of metabolism, and too much of it in our blood can cause harm to our body. It can raise the levels of acidity in your blood, which is damaging to your heart, and even cause suffocation! When you hold your breath by inhaling and then not immediately exhaling, the reason you begin to feel light-headed is not actually due to the sudden lack of oxygen intake, but the excess of carbon dioxide built up in your body. Of course, both are just as important, so make sure to practice proper breathing techniques!
Once the air in your alveoli are enriched with carbon dioxide from the newly oxygen riched red blood cells, this air travels back up the bronchial tubes and out the nose or mouth, in a process called exhalation. At the same time, the pulmonary veins transport the oxygen rich blood back to the heart to be distributed throughout the body. Want to learn a bit more about how all these gases and chemicals work? Check out this basic principles of chemistry course, and part 2 of the same course here.
You can also learn more about improving your breathing in this course.