During inhalation, or breathing in, your diaphragm, a major muscle located beneath your lungs, contracts and moves downward. This action increases the space within your chest cavity. Simultaneously, the muscles between your ribs contract, pulling your rib cage both upward and outward. This expansion of the chest cavity allows your lungs to expand into the increased space. As your lungs expand, air is drawn in through your nose or mouth, where it's warmed and humidified before reaching your lungs. This process is also known as inspiration.
Several sources confirm this process: the National Heart, Lung, and Blood Institute (NHLBI), NIH explains the diaphragm's contraction and the expansion of the chest cavity. MedlinePlus (https://medlineplus.gov/ency/anatomyvideos/000018.htm) further clarifies that this is the first phase of breathing, called inspiration. Other sources, such as Byju's (https://byjus.com/question-answer/what-happens-during-inhalation-and-exhalation/), and ResMed (https://www.resmed.com/en-us/ventilation/respiratory-diseases-conditions/what-happens-during-normal-breathing/) also emphasize the role of the diaphragm and rib muscles in creating the negative pressure that draws air into the lungs.
In short:
- Diaphragm contracts and moves downwards.
- Rib muscles contract, expanding the rib cage.
- Chest cavity volume increases.
- Lungs expand into the increased space.
- Air is drawn into the lungs.
