Diaphragm: Definition & Function

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  • 0:00 The Diaphragm
  • 0:58 Function of the Diaphragm
  • 2:20 Lesson Summary
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Lesson Transcript
Instructor: Adrianne Baron

Adrianne has taught high school and college biology and has a master's degree in cancer biology.

Learn about the diaphragm and how it functions within our bodies to carry out a very vital process. Test your knowledge on the diaphragm by taking the quiz.

The Diaphragm

Take a deep breath in, and now let it out. Guess what? You just used your diaphragm. The thoracic diaphragm, more commonly referred to as simply the diaphragm, is a combination of muscle and tendon that allows you to inhale and exhale. It sits just below your lungs and is shaped kind-of like the top of a dome. It marks the bottom of the chest region and beginning of the stomach region of the body. In addition to fibrous tissue, the diaphragm includes a muscle and tendon. An opening for both the esophagus and trachea exist in the diaphragm to allow them to pass from the chest to the stomach region.

The diaphragm is under involuntary control, meaning that your brain causes it to work without you having to think about it. That's a pretty good thing considering how many things the average person forgets on a daily basis. Can you imagine what life would be like if we had to continuously think about breathing?

Let's look at how the diaphragm carries out this very important function.

Function of the Diaphragm

The diaphragm is the main respiratory muscle that allows us to inhale and exhale. This is done by the contraction and relaxation of the muscle creating a vacuum that sucks air into our lungs through our mouths and noses. When we are ready to inhale, the diaphragm will contract, which causes it to flatten and get closer to the stomach region. Since the diaphragm sits below the lungs, this allows the lungs to expand and creates that vacuum action that I just mentioned. When we are ready to exhale the air back out, the diaphragm will relax and go back to its normal dome shape, thereby pushing up on the bottom of the lungs. The pushing on the bottom of the lungs is a lot like squeezing the lungs, which forces the air back out of the lungs causing you to exhale.

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