How Do Our Lungs Work?

The lungs are one of the most vital components of the human body. They are used every second of the day and without them, we would die in 4-6 minutes. The lungs are located in the thoracic cavity behind your pectoral muscles and behind your ribs. Within the Thoracic cavity, there are two pleural cavities. Each pleural cavity contains one lung. The pleural cavity is created by two membranes and a fluid called pleural fluid. Combined, these structures make it easier for the lungs to expand and contract during inhalation and exhalation.

Within the lungs, there is a combination of many structures that carry air from your oral and nasal airways. These include the bronchi, bronchioles, and alveoli (the major ones). The bronchi is one major airway that brings air to both lungs. The bronchioles are tree-like structures that branch from the bronchi. Finally, the alveoli are the tiny ball-like structures at the end of the bronchioles that oxygen and carbon dioxide transfer through its membrane.

So, we all know how to breathe but, do you know what is actually going on in your body? Breathing is a combination of multiple muscles contracting and relaxing. When breathing in your diaphragm will contract. This increases the volume of the thoracic cavity and thus decreases the pressure of the lungs. When this occurs, the pressure outside of your mouth is higher than in your body. The difference in pressures causes a rush of air through your nasal and oral cavities and into your lungs to try and make the pressures the same. Other muscles that aid in this decrease of pressure include the ribs and intercostal muscles.

When exhaling, the same muscles relaxed and the muscles between the ribs contract, making the volume of the thoracic cavity decrease. This decreased volume causes an increase in pressure and for the same reason air enters your lungs, it will now leave your lungs.

The Heart: The Best Pump Ever!

To stay alive there are a few things that need to occur. One of these things is the transport of nutrients and gases to the cells around your body. If cells were to never receive the required nutrients they would not function properly and die. To make sure that your cells receive the nutrients and gases they need, the heart pumps blood throughout the entire body.


The heart is made of a completely different muscle from anything in your body. This muscle is called Cardiac muscle. Cardiac muscle is defined as being striated, branched, and unnucleated. One of the other most important things to be aware of about heart muscles is that they are not controlled directly by the brain. Instead, they have peacemaker cells that act as separate brains to keep a steady rate.


The Heart has four different chambers. These include the right and left atria as well as the right and left ventricle. These chambers are responsible for receiving and removing blood from the heart. The right side of the heart received blood that is not well oxygenated and pumps it to the lungs. The left side of the heart received oxygenated blood from the lungs and pumps it to the rest of the body to be used.

#32 Top 5 Hardest Classes In College

So far, I am in my junior year of college and I have taken almost all the required courses for a Biology major with a concentration in Biomedical Studies. On top of that I have taken many Honors courses as well as Pre-PA courses (#29 Want To Be a PA? What To Know). Most of these have been difficult but today I will be ranking the 5 hardest courses I have taken thus far.

5. Human Physiology

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This course is usually a combined course with Anatomy at most schools but, Arcadia University separates these classes. This course is a load of fun with some difficult material. All in all, it is one of the easier courses on this list due to its relevance to human life. Many things you learn you will have heard in the past and there is a massive amount of information that you can study from. Its course load is extremely high and it is extremely easy to fall behind. For this reason, it has been listed as the fifth hardest course on my list.

4. Biochemistry

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Biochemistry is an upper-level course that many people avoid. Its prerequisites require that you take General Chemistry I, General Chemistry II, Organic Chemistry, and the General Biology courses. This course is the true bridge between Biology and Chemistry. In this class, you will use Biology concepts such as Glycolysis and Gluconeogenesis and explain them using Organic and General Chemistry. This courses material is difficult in all aspects but, the amount of material is less than other classes on this list.

3. General Chemistry II

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General Chemistry II is often one of the courses you hear many first years complaining about. I am here to say that they are not complaining for no reason (#14 General Chemistry. How To Do Well). If you have taken General Chemistry II you will know the struggle of getting extremely low grades while studying material that is very difficult. The fact is that the equations and concepts taught during this course may be basic to an upper-level Biology or Chemistry major but, to a first-year student, it is like trying to learn a new language. Not only does this class have a difficult curriculum but the curriculum you cover is conceptual. This means you have to be visual and logical as well as knowledgeable about the equations and theories.

2. Comparative Anatomy and Physiology

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Comparative Anatomy and Physiology is not a typical course many people hear about before college. It is sometimes called zoology. This course looks into every development of life from a sponge to a modern human. You begin the semester by learning about sponges and simple forms of life. You will slowly move on to more complex forms of life like arthropods, fish, birds, and eventually humans. What makes this course harder than most courses is that the language between animals is extremely different. Typically for a class, you will begin to see similar words used. However, in this course words will never be the same between species and you will often find yourself trying to keep track of this complex vocabulary. The immense amount of detail and work that is needed for this class is also an immense amount. This is why I have ranked Comparative Anatomy and Physiology second on my list.

1. Organic Chemistry

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Organic Chemistry is notoriously a difficult course no matter where you take it. It is an extremely difficult material to understand is one of the main reasons it is ranked as the hardest course on my list. However, there is an even bigger reason it is ranked as number one. Organic Chemistry is a cumulative class. What I mean by this is that everything you learn from the first to last day builds on top of each other. So, if you do not understand a specific topic or theory, it is not just going to disappear. Everyone learns Organic Chemistry in the same order because without certain knowledge and material you can not solve certain problems. Other classes are not like this. Usually, if you struggle in one area you can do badly on it and move on. Organic Chemistry is not like that and this is why it has earned its spot at the top of my list.