Explain how the diaphragm muscle is able to increase the size of the thoracic cavity even though it doesn't insert into a bone.

Video transcript

Hi, everyone. Let's take a look at this practice problem together. Which of the following happens in the diaphragm. During the inspiration process. The answer options are a, it increases the vertical diameter of the thoracic cavity. B it passively relaxes C, it returns to its original dome shape and D it stops functioning. So, recall that the diaphragm is a dome shaped muscle that separates the thoracic and chest cavities. So let's go ahead and compare and contrast. What happens when the diaphragm is contracted versus relaxed? Now, when the diaphragm contracts, it moves downwards and becomes more flat shaped. So the diaphragm flattens during contraction, when it flattens, this increases the thoracic cavity volume and this causes the lung pressure to decrease, which causes air to flow into the lungs. So, diaphragm contraction produces inspiration. When the diaphragm relapses, it returns back to the original dome shape. Relaxation results in the thoracic cavity volume, decreasing the lung pressure, therefore increases and air flows out of the lungs. So, diaphragm relaxation produces exhalation. So let's go ahead and look at the answer options again. Which of the answer options is true during the inspiration process. Option D it stops functioning is incorrect. The diaphragm does not stop functioning. Option C is also incorrect. The diaphragm does not return to its original dome shape and inspiration. It flattens. So option C is also incorrect. Option B during inspiration, it passively relaxes that is also incorrect. The diaphragm contracts during inspiration. So we're left with the correct answer being, it increases the vertical diameter of the thoracic cavity. The correct answer is option A, it increases the vertical diameter of the thoracic cavity. All right, everyone. I hope you found this helpful and I'll see you soon for the next practice problem.