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What Is The Function Of The Alveoli

by Lyndon Langley
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What Is The Function Of The Alveoli

What Is The Function Of The Alveoli

A person’s lungs take in about 20,000 liters (4,740 gallons) of oxygen each day. This oxygen is then distributed to all parts of the body via a system of capillaries. When we breathe in, our bodies use this oxygen to create energy for our muscles, which contract as a result of the chemical reaction that takes place between the oxygen and certain enzymes within the muscle cells. Our hearts also need the oxygen that enters our bloodstream to pump blood around the body.
This oxygenated blood leaves the heart and goes first to the brain and other vital organs such as the kidneys, liver, stomach, intestines, etc., before it finally reaches the rest of the body. It does so because our bodies have developed highly efficient systems that work hand-in-hand with one another. For example, when you exercise your arms or legs, they become more active because their muscles require oxygen and nutrients to function properly. Your brain needs oxygen too, but unlike the arms and legs, its main priority is not physical activity — it’s thinking! In fact, your brain uses up to 75 percent of the oxygen taken in by the lungs every minute of the day.
In order for your lungs to distribute the oxygen they’ve taken in to your entire body, they must be able to make contact with the blood that flows through them. To do this successfully, these tiny sacs called “alveoli” have developed special structures that allow them to keep pace with the fast-moving blood. These structures include small pores that open directly onto the surface of the lung tissue. These pores, known as fenestrae, are only 0.1 millimeters wide.
Alveoli can vary greatly in size depending upon what part of the lung they’re located in. There are two types of alveolar units — type I and type II. Type I alveolar units are relatively large and contain hundreds of millions of gas-filled sacs. They cover approximately 60 percent of the total area of the lung. Type II alveolar units, on the other hand, make up the remaining 40 percent of the lung. Their sacs are smaller than those of type I alveolar units, but they still manage to hold enough oxygen to provide proper nourishment for the whole lung.
So how do these different sized alveolar units help us? Read on to find out.
Where Are The Alveoli Found?

How Do We Breathe Correctly?

Are there any dangers associated with having too many alveoli?

Where Are The Alveoli Found?
There are three primary areas where the alveoli are found: the trachea, bronchial tubes and the lungs themselves.
Each time you inhale, your lungs expand slightly due to the pressure exerted by the incoming breath. As the lungs increase in volume, the amount of oxygen inside them increases at an even faster rate. However, if the number of alveoles were to remain constant, the amount of oxygen would eventually decrease as the lungs shrink back down to their normal size. Therefore, the number of alveoles per unit area decreases as the lungs get bigger.
The average adult has roughly 1 million alveoli per square centimeter of lung tissue. Since the lungs’ surface area accounts for about 80 percent of the total body surface area, an adult human has approximately 8 million alveoli in his or her lungs. Children have fewer alveoli than adults, averaging 700,000 per cubic centimeter of lung tissue. Babies and young children usually have an average of 500,000 alveoli per cubic centimeter of lung tissue. Older people tend to have higher numbers of alveoli. Men have an average of 940,000 while women have 790,000. And the older a person gets, the more alveoli he or she tends to have. Adults over the age of 65 have an average of 2.2 million, while teenagers have an average of just under 1 million.
Trachea: Located at the entrance to the windpipe, the trachea serves several functions. First, it protects the airway against foreign objects that may enter the throat or windpipe. Secondly, it allows the windpipe to dilate and thus makes it possible for the voice box (larynx), which sits at the top of the windpipe, to vibrate. Lastly, the trachea transports food and water vapor from the mouth to the pharynx, allowing the tongue to form saliva and swallow.
Bronchi: The bronchi serve the same purpose as the trachea except that they transport liquid rather than air. They run along both sides of the windpipe and branch off into smaller tubes, known as bronchioles. Bronchioles branch off again until they end in microscopic alveolar units, which we’ll talk about later.
Lungs: The lungs are divided into lobules, which are further divided into segments. Each segment contains thousands of alveoli. A typical human has anywhere from 2,500 to 4,000 alveoli per lobe. The left lung has twice as many alveoli as the right lung and is responsible for taking in oxygen and expelling carbon dioxide. All together, the lungs account for about 10 percent of the total surface area of the body.
Bronchioles: Also known as terminal bronchioles, bronchioles connect the larger bronchi to the smaller alveolar units. The smallest bronchioles are less than 3 millimeters across; however, most are no wider than 1mm. Most of the alveolar units are connected to a single bronchiole. Air moves from the larger bronchus to the smaller bronchioles by way of intercalation. Intercalation occurs when air pushes its way between adjacent bronchioles without penetrating either wall. Once within the bronchioles, the air splits into individual air channels that go to separate alveolar units. The air channel is surrounded by epithelial tissue that helps protect the delicate lung lining.
Alveolar Units: Made up of multiple rows of gas filled sacs, the alveolus is the basic building block of the lung. From the outside, the alveolus looks like a honeycomb. Within the alveolus, the walls are made up of thin layers of protein fibers that act as filters. Blood vessels lead away from the center of the alveolus, making room for new fluid and gas exchange to occur.

How Do We Breathe Correctly?
Breathing is something we often overlook in favor of talking or eating. But did you know that improper breathing habits can cause damage to the lungs? You see, when we breathe, we don’t inhale fully through our noses. Instead, we exhale partially through our mouths, allowing particles to escape. This results in the buildup of mucus and debris in our throats, sinuses and nasal cavities. Over time, this causes inflammation and swelling. This condition is known as chronic rhinosinusitis.
If you suffer from asthma, emphysema or some other respiratory disease, you should pay extra attention to your breathing techniques. If you smoke, stop smoking immediately. Smoking damages the lungs and weakens their ability to absorb oxygen. If you currently smoke, try quitting today.
An easy way to improve your breathing is to practice using diaphragmatic breathing. Diaphragm breathing involves filling your chest cavity completely with air, forcing the abdomen upward toward the neck and keeping your shoulders relaxed. By doing so, you will force air out of your mouth and nose instead of letting it exit passively.
Are there any dangers associated with having too many alveoli?
No. Having too many alveoli is perfectly fine. What could possibly happen if you had double the number of alveoli? Well, you might develop a tendency to hyperventilate and experience shortness of breath. On the other hand, having too few alveoli could lead to hypoventilation and difficulty breathing. So, the optimum number of alveoli should fall somewhere in between.
To determine whether you have too many or too little, check your pulse oximeter readings. Pulse oximetry measures the percentage of hemoglobin carrying oxygen in your blood. Normal values range from 95 to 100 percent. Anything below 90 percent indicates a problem. Hypoventilation is indicated by a reading below 70 percent. Hyperventilation is indicated by a reading above 15 percent.

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