When we take a deep breath, the air goes down the wind-pipe (or trachea) into the middle of the chest. There the trachea divides into two, then four, then eight - and finally, hundreds of thousands of little airways (or bronchi and bronchioles) in each lung. At the end of each airway is a tiny sac (or alveolus.) Healthy lungs have hundreds of millions of these sacs (or alveoli.)
An upside-down oak tree provides a good example: The wind-pipe is like the large trunk which divides countless times into branches (airways) and twigs (small airways), until at the end of every twig there is a leaf (alveolus). As the wind blows, the leaves move.
Similarly, the air we inhale moves all the way through the lungs to the alveoli. The oxygen in that deep breath is transported through the walls of the alveoli into the red blood cells in the blood vessels (capillaries) that surround each alveolus.
The heart then pumps the oxygen-rich blood through the body and we are able to do things like run up a hill, throw a ball, or surf the web.
One of the by-products of all this web-surfing and ball-throwing, is the build-up of "exhaust fumes" (carbon dioxide) in the body's cells. Red blood cells pick up the carbon dioxide in place of the oxygen they deliver.
Thus, there are two processes at work as we breathe in and breathe out. Blood vessels transport blood that is rich in carbon dioxide and poor in oxygen to the alveoli. And, in the reverse process, the carbon dioxide goes out through the walls of the alveoli, into the airways, and, as we breathe out, back up the trachea.
The lungs expand and contract as we breathe in and out, whereas our ribs are fairly immobile. The pleura, or lining around the outside of the lungs and inside of the ribs, has some lubricating fluid. It allows the lungs and ribs to slide over each other comfortably. It is easy to imagine that, if the pleura is damaged or inflamed, every breath becomes very painful.
However, when we are healthy, breathing is easy - so easy we don't even think about it.
An upside-down oak tree provides a good example: The wind-pipe is like the large trunk which divides countless times into branches (airways) and twigs (small airways), until at the end of every twig there is a leaf (alveolus). As the wind blows, the leaves move.
Similarly, the air we inhale moves all the way through the lungs to the alveoli. The oxygen in that deep breath is transported through the walls of the alveoli into the red blood cells in the blood vessels (capillaries) that surround each alveolus.
The heart then pumps the oxygen-rich blood through the body and we are able to do things like run up a hill, throw a ball, or surf the web.
One of the by-products of all this web-surfing and ball-throwing, is the build-up of "exhaust fumes" (carbon dioxide) in the body's cells. Red blood cells pick up the carbon dioxide in place of the oxygen they deliver.
Thus, there are two processes at work as we breathe in and breathe out. Blood vessels transport blood that is rich in carbon dioxide and poor in oxygen to the alveoli. And, in the reverse process, the carbon dioxide goes out through the walls of the alveoli, into the airways, and, as we breathe out, back up the trachea.
The lungs expand and contract as we breathe in and out, whereas our ribs are fairly immobile. The pleura, or lining around the outside of the lungs and inside of the ribs, has some lubricating fluid. It allows the lungs and ribs to slide over each other comfortably. It is easy to imagine that, if the pleura is damaged or inflamed, every breath becomes very painful.
However, when we are healthy, breathing is easy - so easy we don't even think about it.
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