Breathing is something each of us does all day, every day. Apart from times when we’re feeling ill or exercising, we barely even think about breathing. However, without a properly functioning respiratory system (also known as the pulmonary system), none of us could survive for very long.
This article will give an overview of the respiratory system’s function and inner workings. It will help you gain a deeper level of appreciation for just how miraculous our lungs and other related pulmonary structures truly are.
What Is the Respiratory System?
The respiratory system consists of a group of organs and tissues that all work towards a common goal: to enable us to get oxygen into our blood and carbon dioxide out – in other words, to breathe.
Starting with the nose and mouth and ending with the smallest cells of the lungs, the respiratory system acts to take in air and extract the oxygen we need. It then works in the reverse direction, ridding our body of gaseous waste products, such as carbon dioxide, that develop during everyday cellular processes.
Respiratory System Function
All body processes and functions can be discussed at very deep levels of complexity or more simply at the surface level.
In general, the respiratory system functions by creating a pressure differential between the air outside our body and the air inside our body. In doing so, air can either rush in (as we inhale) or rush out (as we exhale). Enabling this process are a few different muscles and structures.
One of the most important active tissues involved in the respiratory process is the diaphragm. In the next section, we’ll discuss the role of the diaphragm and other pulmonary tissues within this system.
Parts of the Respiratory System
Breathing requires coordination between a few key structures. In this section, we’ll discuss the various organs and tissues that participate in respiration.
The Nose and Mouth
At the beginning of the breathing process, we find our two main airways: the nasal cavity (nose) and the mouth. These are the passageways through which air travels to reach the deeper portion of our respiratory system.
The nose specifically can act to warm the air and clear it of various particulates, such as dust. In doing so, the lungs have an easier job extracting the essential elements our bodies need. The mouth cannot perform these roles.
The Pharynx, Trachea, and Bronchi
Next come three short tubes (which increase in complexity at each deeper level) that serve to direct the air towards the lungs and away from the digestive system: the pharynx, the trachea, and the bronchi.
These structures should primarily be thought of as conduits that shunt and guide the air toward their ultimate destination: the lungs on the way in and the atmosphere on the way out.
The bronchi, for their part, branch multiple times as they get closer to the lungs. Specifically, looking closer at these structures shows there are primary, secondary, and tertiary bronchi, which then lead to bronchioles. The bronchioles are the last structures before the air reaches the cells of the lungs themselves, known as alveoli.
While all parts of the respiratory system are important for good pulmonary health, the lungs can be thought of as the VIP. The lungs literally take in air, extract oxygen and other needed elements, and deliver said items to various parts of the body. At the same time, the lungs work to expel carbon dioxide and other waste products that cannot be effectively used by our bodies.
At the smallest level, the lungs are made up of cells known as alveoli. The alveoli are the specific site of gas exchange, where carbon dioxide and oxygen are essentially “traded” during each breath in and each breath out.
Muscles of the Respiratory System
The respiratory system uses pressure differences to bring air in and out. These pressure differences can be created by a few key muscles.
Perhaps the most important muscle of the respiratory system (and arguably the body as a whole) is the diaphragm. The diaphragm works all day long to help the lungs expand and contract. This muscle is absolutely critical to our survival.
Other notable muscles involved in respiration (especially respiration during heavy activity) are the intercostals. These muscles attach between the ribs and serve to expand and contract the rib cage, particularly during labored breathing.
How Do We Breathe?
Now, let’s put it all together!
When we take a breath in, the air travels through our nose (or our mouth directly to the pharynx), through our nasal cavity, on to our pharynx. From there, the air is directed through the trachea and into the primary bronchi. The primary bronchi then split into secondary bronchi. The secondary bronchi then branch into tertiary bronchi before reaching their final destination in the alveolar cells of the lungs.
At this point, gas is exchanged and nutrients are sent to where they are needed in the body via the circulatory system (a system to be discussed on another day!).
But the lungs’ job is never complete. As soon as the air reaches the alveoli, waste products then need to be sent in the opposite direction through the system, ultimately being exhaled into the atmosphere.
If you’re like most people, this overview of the respiratory system has probably brought up some questions. Let’s take a look at some of the most frequently asked questions pertaining to the pulmonary system.
How Many Times a Day Do We Breathe?
Depending on disease processes, athletic ability, and various other factors, the number of breaths you take in a day may be very different from your neighbor Still, a 2017 study1 found that most people breathe about 10–20 times per minute. With 1440 minutes in a day, that comes to a grand total of 14,400–28,800 breaths daily!
How Much Oxygen Do We Take In per Breath?
While this is a very difficult item to study, researchers in the 1990s2 were able to conclude that the lungs consume roughly 5-6 ml of oxygen per minute. With the average person taking roughly 15 breaths per minute, we can then conclude that each breath we take results in roughly 0.37 ml of oxygen being taken up by the lungs.
However, this is a particularly difficult area of study due to the methods needed to collect the data in question, the differences in partial pressure of oxygen at different altitudes, and a variety of other factors.
How Do We Breathe When We Sleep?
Because breathing is largely controlled by unconscious processes, we don’t need to worry about ceasing to breathe while we sleep.
Everything in our bodies is controlled by parts of our nervous system. Many of these processes, especially those that keep us alive, are largely controlled by the autonomic nervous system. This portion of our nervous system takes care of business without any conscious input from us.
That being said, if we want to take over conscious control of our breathing, we can. For example, if you want to start breathing faster or slower right now, you can do it!
If you’re interested in learning more about sleep, breathing, and the respiratory disorders that affect these processes, check out this study by Choudhary.3
Conditions Affecting the Respiratory System
There are tons of different factors that can alter our respiration. For instance, pollutants in the atmosphere can make it harder to breathe.
Additionally, there are a host of diseases and conditions that affect the respiratory system. In this section, we’ll review a few of the most common pulmonary system disorders.
Chronic Obstructive Pulmonary Disorder, or COPD, is a condition that affects an estimated 328 million4 people across the globe. Essentially, this general term refers to any condition which “obstructs” the respiratory system in some way. For instance, emphysema and chronic bronchitis are both considered to be obstructive pulmonary diseases. When they last for a long time, they are called chronic.
These conditions can make it very hard to take quality breaths on a daily basis. People with COPD are often prescribed supplemental oxygen to help them cope with the issues they experience.
Asthma is a life-threatening condition in which the airways can become inflamed in response to a “trigger.” Triggers can be many things including excessive exertion, pollutants in the atmosphere, and even stress.
Most people with asthma will never go far without their rescue inhaler, which can help to expand the airways should they experience an attack.
Cancer of any kind is no small matter. But lung cancer is responsible for more deaths than any other cancer.5 This devastating disease often spreads quickly to other tissues, and few people who develop lung cancer are able to fully recover. If you have a cough that lasts for more than three weeks, see your doctor just in case it is a sign of lung cancer; the sooner you catch it the better chance you have.
When a person suffers from pneumonia, the alveoli in the lungs become filled with fluid. Typically, this happens as the result of an infection that reaches the smallest cells of the respiratory system. This makes it hard or impossible for them to fulfill their role as gas exchange sites. The underlying infection must be treated to make the pneumonia go away.
Genetics can play a huge role in disease processes. Cystic fibrosis is caused by a defect in a specific gene. Specifically, cystic fibrosis causes a problem in the cells that produce fluid in the body. This can cause many issues in the respiratory system and elsewhere.
In the past, only a handful of people with cystic fibrosis would live more than a few years. Now, however, we have developed some therapies and technologies that can allow these patients to lead relatively normal lives.
When Should You See a Doctor About a Respiratory Condition?
No one likes going to the doctor. After all, going to the doctor can often force us to face the reality that we truly are sick, and that we need help to manage a disease.
That being said, if you’re noticing symptoms that aren’t resolving in a normal time period (a few days to a week), you should get to the doctor ASAP.
As the ancient saying goes: “one disease: long life; no disease: short life”. This hints at the fact that those who know what is wrong with them and acknowledge they have a disease can take steps to address it, and will live a long, fruitful life. Those who avoid going to the doctor or investigating their symptoms may allow a more serious disease to take hold, and may live a shorter life.
- Russo, M. A., Santarelli, D. M., & O’Rourke, D. (2017). The physiological effects of slow breathing in the healthy human. Breathe (Sheffield, England), 13(4), 298–309. https://doi.org/10.1183/20734735.009817
- Loer, S. A., Scheeren, T. W. L., & Tarnow, J. (1997). How Much Oxygen Does the Human Lung Consume? Anesthesiology, 86(3), 532–537. https://doi.org/10.1097/00000542-199703000-00004
- Choudhary, S. S., & Choudhary, S. R. (2009). Sleep effects on breathing and respiratory diseases. Lung India, 26(4), 117–122. https://doi.org/10.4103/0970-2113.56345
- Quaderi, S. A., & Hurst, J. R. (2018). The unmet global burden of COPD. Global health, epidemiology and genomics, 3, e4. https://doi.org/10.1017/gheg.2018.1
- Centers for Disease Control and Prevention. (2022, February 28). An Update on Cancer Deaths in the United States. Centers for Disease Control and Prevention. https://www.cdc.gov/cancer/dcpc/research/update-on-cancer-deaths/index.htm