Bronchi: Anatomy, Function & Definition

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  • 0:01 Why Do We Breathe?
  • 0:45 Bronchi: Anatomy and Function
  • 3:00 Diseases of the Bronchi
  • 4:00 Lesson Summary
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Lesson Transcript
Instructor: John Williams
Ever wondered how air makes it from your mouth and nostrils to your lungs? Or how carbon dioxide brought to the lungs gets expelled through the oral and nasal cavities? Well, the bronchi are a key component, and in this lesson, you will learn about their role in breathing.

Why Do We Breathe?

Take a deep breath. Now blow it out slowly. The air that you took in, or inhaled, during the breath is filled with oxygen, which your body needs to produce energy for cellular activities. The air you blew out, or exhaled, is filled with carbon dioxide, which is a waste material in the human body, and gets removed during exhalation.

Breathing is the method by which the human body exchanges oxygen from the environment with carbon dioxide within the body. This is a major function of the respiratory system, and the organs that are responsible for the exchange of these gases are the lungs. But what about the pathways between the nose, mouth, and the lungs? What are their roles in this process?

Bronchi: Anatomy and Function

The bronchi, singularly known as a bronchus, are extensions of the windpipe that shuttle air to and from the lungs. Think of them as highways for gas exchange, with oxygen going to the lungs and carbon dioxide leaving the lungs through them. They are part of the conducting zone of the respiratory system. The conducting zone, which includes the windpipe and pharynx, is a region of the respiratory system that only moves air in and out of the body and is not a part of the gas exchange process.

Each bronchus contains cartilage, a mucosal lining, and smooth muscle. Cartilage is a connective tissue that provides support for physical processes and, in this case, it prevents the collapsing of the bronchi during inhalation and exhalation. This is important, since air conduction involves pressure that can damage soft tissue if not protected. The mucosal lining produces mucus, which is a thick, semi-liquid substance designed to trap foreign particles from entering the lungs.

Smooth muscle is also found in each bronchus. It is muscle that is involuntarily controlled, which means you can't control it yourself. Your body determines whether this smooth muscle contracts or relaxes based on whether or not more or less airflow is needed.

Picture this: You are walking in the forest, and a bear is standing in front of you. The bear growls. In your moment of panic, you take off running. Once safely away from the bear, you realize that you are panting and breathing heavily.

During emergency situations, such as the one presented above, breathing is vital to surviving. More oxygen coming in means more energy being produced by the cells that are necessary for escape, including your muscles. In cases like this, the body releases norepinephrine, an emergency hormone, which will cause smooth muscles in the bronchi to relax, allowing more air to come into the lungs and more oxygen to be delivered to the necessary tissues. This is true for any exciting or emergency situation, whether it is winning the lottery, playing sports, or running away from the bear above.

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