Gas Exchange in the lungs
Exterior view of Alveoli. This is
where gas exchange takes place in the lungs.
are tiny balloon-like sacs, in the lungs, where gas exchange takes place and they serve
as the barrier between the external environment (the air)
and the internal environment (the blood).
Because gas must exchange in a second or two between
blood vessels and the air inside of our lungs, how do you suppose the
process is made efficient?
- These small sacs have very thin
walls that are full of blood vessels called capillaries. The walls are
so thin that the oxygen, brought in during inhalation, can diffuse through
them to enter your blood.
- Likewise, carbon dioxide is carried by your
blood to the blood
vessels in the alveoli where it diffuses through the thin walls and into
the air in your lungs. That "used" air is now ready for exhalation. Each lung
has millions of alveoli, and your body needs all of them to get enough
oxygen into your blood!
are there so many capillaries at the alveoli? Why are they shown in
blue and red?
What is the problem
with the buildup of tar and other hazardous materials from smoking in the
Why are dust masks
so important for some jobs?
Okay, it is not really blue. Blue blood is more of a
dark red color, close to maroon. However, during surgery and
dissections, the veins that carry this blood appear blue. This
change in color is due to the lack of oxygenation in the hemoglobin of the
What color is oxygenated blood? (Hint: The answer is
(blue) blood travels into the capillaries surrounding the alveoli. The
blood drops off its carbon dioxide molecules and picks up oxygen. Once
the blood cells pick up oxygen, it becomes oxygenated (red) blood. The
blood now exits the pulmonary capillaries and carries oxygen to all the
tissues in the body.
blood does contain oxygen, but it is present at a smaller
concentration than oxygenated blood. The term deoxygenated is
used for convenience.
Does anybody really
have blue blood? Why do bruises appear blue at first (they change to
a yellowish color later, as the blood is chemically broken down)?
involved in Gas Exchange
requires the help of a muscle known as the diaphragm.
- The diaphragm
is a large, sheet-like muscle at the bottom of your chest cavity. It helps
you exhale and inhale by moving up and down, respectively.
- When your diaphragm
contracts (moves up), you inhale air.
- When your diaphragm
relaxes (moves down), you exhale air.
- Without your diaphragm, you lungs couldn’t fill
up with fresh air or push old air out.
Why do you think
the diaphragm is located at the bottom of your chest cavity?
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