What happens to the air we breathe?
Air goes in, air goes out. But what actually happens to the air we breathe?
1) Nose
A normal, healthy breath starts its journey at the nostrils. Passing swiftly into the labryinth of the sinuses.
The intricate, maze-like structres of the sinuses act as an ‘air-conditioner’, humidifying the air, while also filtering out harmful pollutants and pathogens.
If we breathe in through the mouth, the air bypasses this process.
2) Lungs
This ‘conditioned’ air then makes its way to the throat, descending down the windpipe (trachea). Eventually, it reaches a fork, where the windpipe branches off into two bronchi, one going to the left lung and the other to the right.
When you travel far enough along the length of a tree trunk, eventually it will start to expand, into branches. Similarly, the bronchi spread out into thousands of branches, known as the bronchioles.
At the ends of a tree branch we typically see an abundance of leaves. Likewise, at the ends of the bronchioles we find millions of tiny air sacs, known as the alveoli.
3) Red blood cells
Air is a mixture of several gases-,of which oxygen only accounts for ~20% and carbon dioxide (CO2) a meager 0.04%.
The alveoli are surrounded by capillaries (small blood vessels) loaded with red blood cells.
The walls of both capillaries and alveoli are extremely thin, allowing oxygen and other gases to easily flow from one to the other.
As oxygen molecules enter the blood stream, they are picked up by red blood cells. We can picture red blood cells as ships or ferries, filled with millions of seats (haemoglobin).
Freshly loaded with passengers (oxygen molecules), these oxygenated blood cells embark on their voyage to the heart, and onward throughout the body.
4) Tissue Cells
Oxygen is required for various process throughout the body, one of those being in tissue cells, that need oxygen to generate energy.
When oxygenated red blood cells pass close by these tissue cells, they offload their oxygen ‘passengers’.
Once inside the cell, these oxygen molecules are snapped up by mitochondria. Where they are combined with glucose, to generate energy, in a process called cellular respiration.
One of the by-products of this reaction is CO2.
5) And back
From here the red blood cells begin the return leg of their voyage.
We now now red blood cells transport oxygen molecules, but that’s not all, they can also carry CO2!
Most of the *waste CO2 molecules from cellular respiration dissolve directly into the water of the bloodstream. However, some of these molecules hitch a ride on red blood cells, alongside any leftover oxygen molecules.
With the red blood cells having offloaded most of their oxygen, the blood is now deoxygenated. This deoxygenated blood courses through the veins, back to the heart.
From the heart, they go back where the journey started, to the capillaries of the lungs.CO2 molecules exit the plasma and red blood cells, flowing into the alveoli, ready to be exhaled.
In one simple breath, this ‘waste’ air travels backwards, up the tree-like pathway of the lungs, up the throat, and out from the nose (or mouth).
…aaaaand repeat. 20,000+ times a day 🌬️