Let’s Talk About Airways

COPD is a disease that impacts your airways and alveoli. In an earlier post I talked alveoli and the role they play in COPD. Today I’d like to begin the discussion about airways.

So, that said, let’s begin our discussion.

What are airways?

It would seem logical to assume most of us in this community know what airways are. After all, they do play a significant role in the disease this community is all about. For this post, we can define them as the passages air takes to alveoli, where gas exchange occurs.

Of course, you inhale air. This air travels through your nasal or oral cavities. These are your largest airways.

Along the walls of your nasal passages are small-bony-like structures. These are called turbinates. Their job is to warm and humidify the air that you inhale. Your nasal passages are also lined with mucus and tiny hairs. These act as filters to trap pathogens (such as viruses) or other irritants (such as tiny particles) in the air you inhale.¹

Your mouth offers less resistance to the flow of air. So, this is why many of us breathe through our mouths when we exercise. Although, your nose is far better at warming, humidifying, and filtering than your mouth. So, for this reason, most of us breathe through our noses most of the time.¹

So, air enters your mouth or nose. It travels to the back of your mouth and nose to the pharynx area. From here, air travels to your trachea and then to your lungs.¹

Your trachea is surrounded by C-shaped cartilage. This cartilage helps your trachea keep its shape, such as when you exhale or cough.^1-2

Branching off from your trachea are two main stem bronchi: your right main stem bronchi and your left main stem bronchi. Your right main stem bronchi branch off to form three lobar bronchi. These carry air to your right lung. Your left main stem bronchi branch off to form two lobar bronchi. These carry air to your left lung.²

Lobar bronchi further branch out to form segmental bronchi. These carry air to the various segments of your lungs. These further branch out to form many subsegmental bronchi. ^1,2

Like your trachea, bronchi are surrounded by cartilage. Although, this cartilage starts to disappear as your bronchi get deeper and deeper into your lungs.^1-2

Subsegmental bronchi further branch out to form bronchioles. These bronchioles continue branching out. The smallest bronchi are called terminal bronchi. And they lead air to its final destination: your alveoli.^1-2

What are conducting airways? 

Your conducting airways include your trachea, mainstem bronchi,  bronchi, and bronchioles. Their job is to allow the free and easy passage of inhaled air to the areas of your lungs that participate in gas exchange. Your bronchioles are often referred to as your small airways. It is changed to these airways that contribute to our disease.^3-4

The smallest bronchioles are called respiratory bronchioles. They are surrounded by those tiny grape-like structures that we call alveoli. These respiratory bronchioles and alveoli are called the “gas exchanging zone.”^1-4

Gas exchange occurs when oxygen from the air you inhale enters your bloodstream. It also involves a waste product called carbon dioxide. While oxygen enters your bloodstream, carbon dioxide leaves your blood and enters your lungs. Oxygen then travels to all the tissues of your body. And carbon dioxide is exhaled into the air around you.

So, as you can see, your bronchi continue branching out. This is also true of your bronchioles. With each branch, your conducting airways continue getting smaller and smaller. The smallest conducting airways are called terminal bronchioles.^1-4

Like your nasal passages, the inside walls of your bronchi are covered with a mucous layer. This mucus is secreted by special cells scattered along their walls called goblet cells. The inside walls are also lined with special cells that contain small, hair-like structures called cilia.^1-4

The largest bronchioles are surrounded by cartilage, although this cartilage gradually disappears as these airways get smaller and go deeper into the lungs. The largest bronchioles also have mucus glands and mucus. But these also start to disappear as these airways get smaller and go deeper into the lungs.^1-4

The mucus traps any pathogens or particles your nose may have missed. It also further warms and humidifies inhaled air. Once air travels to the gas-exchanging zone, inhaled air is free and clear of germs and particles. It is also humidified and warmed to body temperature.^1-4

What is your bronchial tree? 

You can visibly see your bronchi and bronchioles if you dissect your lungs. Together, they give the appearance of a tree, only upside down. This tree has a name: the Bronchial Tree.

As your airways continue branching out, they form 23 generations of airways. The first 15 generations are part of your conducting airways.

Conducting airways are further divided into the upper airway and lower airway. Your large airways consist of your trachea, bronchi, and a couple of generations of bronchioles. Your small airways consist of your bronchioles from about the 8th generation down to terminal bronchioles.³