How do we breathe?

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I know that the diaphragm expands causing the air to leave the lungs. But what happens when the diaphragm contracts? How does this draw air in to the lungs?

In: Biology

5 Answers

Anonymous 0 Comments

Think of it like people who snap their gum vs blowing bubbles. By creating a seal with the gum around their mouth to the outside, and then opening their mouth cavity larger, it pulls the gum inward expanding an inverse bubble. That’s how your diaphragm contracting expands your lungs to draw in air (though, hopefully without the pop at the end…)

Anonymous 0 Comments

When you expand your lungs it results in a pressure differential between the atmsophere around you and the space in your lungs. To resolve this differential air rushes in. It’s the same thing in reverse to letting go of a ballon that is not tied and the air rushing OUT – the pressure inside the balloon is higher than in the atmosphere. You use your muscles to expand the chest cavity and create a void in the space that is low pressure – air then fills it.

Anonymous 0 Comments

It’s like a syringe: you pull to fill it with air, and you push to empty the air out through the needle.

The diaphragm muscle can do this, and so can your chest/rib muscles. You can actually activate them either or, if you concentrate (breathe “with your stomach” vs. breathe with your chest).

Anonymous 0 Comments

When the diaphragm contracts, it creates a negative pressure difference. Physics wanting things to balance out, fills the vacuum created with air.

Anonymous 0 Comments

When muscles contract they get shorter. The diaphragm is like an umbrella with the curve cavity on the lower side (facing your internal organs like liver and stomach). If it shortens, it gets flatter, which means the dome part will get lower into your abdomen, this means the space inside your rib cage becomes larger. Your lungs are surrounded by thin layer of fluid that has no access to air or other large movement of fluid. If the thoracic wall is pulled away (bigger cavity in it), the fluid between the wall and the lungs cannot expand, and so the lungs get stretched in many directions too. At the same time, your ribs are like stacked circles that are not horizontal but declined, and when you inhale you flex some muscles that cause the ribs to get more horizontal, so this pulls the ribcage outwards also expanding the space inside it. When you expand the space of any gas filled cavity, the pressure in it drops, and since your lungs are open to the atmosphere when you inhale, dropping the pressure in them forms a pressure gradient so the air rushes from the outside to the lungs. Then you relax the diaphragm and rib cage muscles, ribs fall back to their declined position and the diaphragm dome rises again as that’s it’s physical shape. This decreases the space again, increasing pressure and expelling air out. You can also forcefully exhale by flexing some muscles in your rib cage to force the ribs down stronger and quicker. In general, exhalation is passive, but when you are running and need quick gas exchange for example, you begin to recruit muscles like these.