The Causes of Chronic Obstructive Pulmonary Disease (COPD)

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  • 0:27 Your Airways
  • 1:07 COPD
  • 4:27 Obstructive Diseases
  • 5:20 Signs & Symptoms
  • 6:01 Treatment Options
  • 7:13 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

This lesson explores the causes of obstructive lung disease, including COPD, emphysema, and chronic bronchitis. We'll also discuss asthma, cystic fibrosis, and bronchiectasis.

Breathing Difficulties

Let's try and make this lesson interactive. Breathe in. Breathe out. Breathe in. Breathe out.

There are only two things you did there. You pulled breath in and then you pushed it out. Simple enough - unless your lungs are sick as the result of an obstructive disease. An obstruction increases resistance to airflow, and suddenly, breathing isn't so simple anymore.

A Quick Overview of Your Airways

Think of the respiratory system as a tree. The lower parts of the respiratory system are like a tree's root system. Trees have a big main root that shoots down into the ground. The big main respiratory root that shoots down into your body is your trachea. This root then branches off into smaller offshoots that we call bronchi. The offshoots branch into the smaller bronchioles. Finally, the bronchioles terminate in little root nodule-looking things we call alveoli. The alveoli are colloquially known as the air sacs.

Chronic Obstructive Pulmonary Disease

Unfortunately, these airways can suffer from a myriad of conditions, some of which increase resistance to airflow as a result of obstruction.

One of these conditions is chronic obstructive pulmonary disease, or COPD. COPD is a respiratory condition characterized by chronic airway inflammation, scarring, and mucus production, leading to difficulty breathing, usually as a result of smoking. COPD classically encompasses emphysema and chronic bronchitis.

Emphysema refers to the irreversible enlargement of alveoli with a resulting decrease in function. Here's the lowdown in normal speak. When you smoke, you introduce a lot of bad stuff into your lungs. This stuff is interpreted as something dangerous by your body. The body then initiates an inflammatory response to try and protect itself against the toxins in the smoke. This inflammatory process destroys the normal tissue architecture around the air sacs. This causes the air sacs to become larger, less numerous, and more floppy.

Think about it. Look at a honeycomb. Each honeycomb cell is like one alveolus. If you destroy the walls between the cells, they will coalesce into fewer but larger cells. They'll become floppier because their remaining walls are less rigid. That's what happens to alveoli in emphysema.

This is very bad news for the person who is trying to breathe. First of all, the surface area for proper gas exchange is decreased. The elasticity of the alveoli is also decreased. Elasticity is what rubber bands have. Stretch one, and then let go. Elasticity is the property that restores the normal shape of the rubber band once you let go of one end. As you breathe in, the alveoli stretch. As you breathe out, they spring back into shape to push the air out. But during emphysema, the flappy alveoli cannot properly spring back into shape, leading to improper exhalation.

All of this is further compounded by the fact that, in emphysema, the destruction of the normal airway architecture causes the bronchioles supplying them with air to collapse, leading to obstruction of the airways. This means that air is actually trapped in the lungs in emphysema.

The other half of COPD is the chronic bronchitis I mentioned before. Chronic bronchitis most importantly refers to a longstanding inflammatory process that leads to clogging of the airways with mucus as a result of mucous gland hyperplasia. Basically, in chronic bronchitis, the glands that produce the mucus multiply and secrete a lot of gooey stuff that clogs up the airway. Just go ahead; try to breathe out of a straw that is stuffed with wet paper, representative of mucus plugs. It's going to be kind of difficult to do that due to the obstructed straw, which is representative of your airways.

Other Obstructive Pulmonary Diseases

Another major obstructive cause for pulmonary disease is definitely something you know at least a little bit about. It's asthma, a chronic condition where hyper-responsive airways cause airway constriction and inflammation. So, something like dust, pollen, or even cold air can trigger the airways to constrict, increasing resistance to airflow. Asthma, unlike COPD, causes reversible constriction of the airways.

Besides asthma, another cause of obstructive pulmonary disease is bronchiectasis, which refers to the abnormal dilation of bronchi, with impaired airway secretion clearance and airway collapse.

Finally, cystic fibrosis, a genetic disorder that leads to very thick and viscous secretions, causes airway obstruction as well.

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