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Breathing Lungs Respiration

What are we learning?

How do animals breathe? Breathing is:

bringing O2 from the air into their bodies.

removing CO2 from our cells, and sending it out into the air.

Why are we learning this?

• Merely bringing air into your mouth or lungs won’t oxygenate cells in the rest of your body.

• So there must be a way for O2 to get to all your other body cells.

•  Also, every cell produces waste chemicals, like CO2.
We’ll see how this waste is transported out of the body.


Trachea, Bronchi Alveoli, Diaphragm

How do we pull air from the outside into our lungs?

The diaphragm is a muscle that controls the lungs

As diaphragm is pulled down,

volume of lungs increases. Air pressure in lungs drop

So air rushes from the outside, down into lungs,
until the pressure inside = pressure outside

diaphragm lungs 1

from Dynamicscience.com.au

As diaphragm moves back up

volume of lungs decreases. Air pressure in lungs increases

So air rushes out of lungs,
until the pressure inside = pressure outside

diaphragm lungs 2

from Dynamicscience.com.au




Nose and mouth: This where air enters. It is warmed and filtered

Then goes down the trachea (windpipe)

A tube made of cartilage that connects the back of the throat to the lungs.

Trachea splits into two tubes: left bronchus and right bronchus.

This happens so that each lung gets air

Each bronchus branches out, like a tree branches.

The smaller air tubes (branches) are called bronchi

At the very end of each pathway is a gas-exchange organ called the alveoli.

Alveoli are where O2 molecules enter your blood, and where CO2 molecules leave it

Lungs Bronchi Lobes Alveoli Pleura


Gas exchange in alveoli

In the lungs:

Air with O2 enters as we inhale.

O2 diffuses thru the alveoli walls

O2 gets absorbed into RBCs (red blood cells)

At the same time – CO2 gas diffuses from RBCs thru alveoli walls,
and goes out into the alveoli. Then it gets exhaled.

Look at colors: RBCs turn from dark red to bright red when oxygenated

The narrow blood vessels – that carry RBCs one-at-a-time – are called capillaries.


Outside the lungs, in the rest of the body

Everywhere else in your body, cells need O2.

RBCs are in capillaries. They give off their O2 wherever needed

O2 passes right thru capillary walls, into nearby body cells.

At the same time – all body cells create waste gas, CO2

This CO2 floats out of them, and diffuses right thru capillary walls, and gets picked up by RBCs.

Then the RBC (filled with CO2) goes back towards the lungs.


Path of blood from lungs, to heart, and thru body

First consider this diagram. You can trace the path of the blood:

Pulmonary circulation

1. De-oxygenated, dark red blood, in veins
2. Vena cava
3. Right atrium
4. Right ventricle
5. Pulmonary artery  (towards the lungs)
6. Lungs – Where blood is oxygenated
7. Pulmonary vein (towards heart)
8. Left atrium
9. Left ventricle
10. Aorta
11. Arteries branching out to the rest of the body

Here we can follow animated flow of blood.

systemic circulation heart lungs

from artandsciencegraphics.tumblr.com


Why do cells require O2?

Cells use oxygen during cellular respiration to generate energy.

Breathing isn’t usually consciously controlled

It usually “just happens”; your brain directs your lungs to take air in-and-out automatically.

What happens if you are exercising, and your body needs more oxygen?
Do you need to remember to breath more? Nope.

Your nervous system takes care of this for you.

There’s a part of your brain – medulla oblongata – that regulate breathing by monitoring blood CO2 levels.

If blood CO2 levels get too high, then the brain sends impulses to the diaphragm and chest muscles that increase the breathing rate.

This rids the body of excess CO2 while bringing more O2 to the blood.

Medulla oblongata blood CO2 oxygen

image from interactive-biology.com/107/what-parts-of-the-brain-control-respiration/

Ways of breathing in animals

This infographic is from Elaenor Lutz, from her website at tabletopwhale.com

Amazing 3 ways animals breath GIF large


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