Which Of The Following Refers To The Movement Of Air Into And Out Of The Lungs?

The following is a question that was asked to me recently at an interview for a job. You may think it’s simple enough, but you’d be surprised how many people get this wrong.
Question: What is Ventilation?
Answer (from my perspective): This is probably one of those things that most people take for granted. But there are some interesting questions here. First we need to define ventilation. In order to do so, I’ll first explain what ventilation is not.
Ventilation is NOT Breathing
Breathe is something that happens inside your body, while ventilation is something that moves outside your body. So ventilation does not mean “breathing”. You don’t breathe through your nose and mouth. Your heart beats, which causes blood to move throughout your body with great speed. That movement creates heat. When that warm blood reaches your skin surface, it cools down and becomes vapor. As it evaporates, the moisture condenses into water droplets. These tiny drops then travel towards the cooler parts of your body – like your feet. When they reach these areas, the water droplets condense again into liquid form, which runs down your legs until they finally become part of our large scale circulatory system. This is known as evaporation-condensation cycle.
You see, ventilation means moving fresh air over the outer layer of the skin, where the sweat glands are located. Sweat produced from evaporation is released into the external environment, allowing the evaporation-condensation cycle to continue.
There are two kinds of ventilation; natural and artificial. Natural ventilation refers to the normal function of the human respiratory system and includes both inhalation and exhalation. Artificial ventilation refers to the function of mechanical ventilators used in hospitals when the natural mechanism is impaired.
Inhaling Fresh Air
When we inhale, we suck in oxygen and carbon dioxide. The whole thing takes place in our chest area. During the intake process, the diaphragm contracts and forces the air into the lower portion of the lung, where the alveoli are found. There the oxygen gets dissolved and absorbed. Afterward, the gas mixture passes into the trachea and further on to the bronchi. From there, the fresh air enters into our entire body via the bloodstream, including our brain. Carbon dioxide is also taken up in this manner.
Exhaling Exhaust Air
As soon as fresh air enters the body, its carbon dioxide content starts to increase. Therefore, exhaling fresh air is necessary to keep the level of CO2 within healthy limits. During exhalation, the diaphragm relaxes and allows the exhaled air to pass upwards. At the same time, the muscles around our upper ribs expand, pushing the stale air outwards. Then the stale air is pushed downwards through the bronchioli, eventually reaching the lungs’ bottom. Here it mixes with the incoming fresh air. From the lungs, the exhaust air travels into the atmosphere via the trachea and further on to the rest of the body.
How Does Our Chest Work?
Our chest works pretty much the way our lungs work. Just like our lungs have their own structure, our chest has its own structure too. The chest wall consists of bones, cartilage and ligaments. On top of that, there are internal organs such as the rib cage, breastbone, sternum, clavicles, etc. All these structures together create a protective barrier between us and the world.
This protection is needed because our chest is exposed to various harmful factors. For example, the temperature around our chest area changes very rapidly. Also, there are certain chemicals that enter our bodies during respiration. Furthermore, our chests are subjected to injuries from falls, car accidents, sports activities, etc. Finally, our chest walls are constantly under attack from germs and viruses.
All these threats require special care and attention. One important element that protects our chest is called pleura. Pleura is a thin membrane that covers the lungs and separates them from the chest cavity. Pleura plays a significant role in protecting our lungs from diseases, chemical attacks and other negative effects. It also helps keep our lungs moist.
Finally, let’s talk about how our chest expands and contracts. We know that breathing involves expansion and contraction. However, it turns out that our chest actually expands before we take in a breath! Why is this so? Well, our chest expands naturally due to the fact that our rib cages are attached to our pelvis bone. Ribcage expansion comes prior to the actual inspiration process.
After all, if our chest expanded before taking in a breath, wouldn’t we run out of room in our chest after taking in a big gulp of air? No, because the expansion occurs in our chest itself, rather than in our chest cavities. This is why our chest never feels full even after taking in a huge amount of air.
That said, let’s go back to the original question. Which of the following statements best describes ventilation?
1) Ventilation is the act of moving fresh air over the outer layer of the skin, where the sweat glands are located.
or
2) Ventilation is the act of moving fresh air over the outer layer of the skin, where the sweat glands are located.
I chose option 2 because that is the correct answer. The reason being that ventilation is simply moving fresh air over the outer layer of the skin. Once you understand this concept, you will realize that everything else follows logically.

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