Today a large number of scientists are working very hard to learn more
about the body systems that affect gas transport and the diseases that
affect it. Let's take
a closer look at how they discovered the things we know about the respiratory
How do we measure breathing?
A spirometer is a piece of equipment that scientists use
to measure lung capacity and the amount of air a person normally breathes
in and out. You will have an opportunity to make
your own spirometer in activity #1.
A modern electronic spirometer
Basic idea of measuring air exchange, using a
"spirometer." As air is taken in (from the
"oxygen chamber" in the apparatus on the left), the
floating drum drops down. At the same time the writing arm on the
recording drum moves up, indicating inhalation. Opposite effects
occur during exhalation.
How can you make a good estimate of the amount of air you breathe
in a day?
- One way to do this is to multiply the amount of air you breathe in one breath
x the number of breaths you take in a minute x 1440, which is the number
of minutes in a day.
- Can you think of any other ways?
Every day our body breathes in and out as much as 10,000
liters of air. If we were talking about soda, this would be enough
soda to fill 5000 two-liter bottles. 5000 bottles of soda weigh
about the same as 11 average size cars. Knowing that a bottle of soda ways about 4.4 pounds and
an average size car ways 2000 pounds, can you figure out how to make this
calculation? (Click here for the
You can make a good estimate of how much air you breathe in and out everyday. To
do this observe your breathing rate by counting the number of breaths
you take in a minute and use a spirometer to figure out how much
air you breathe in during a single breath at rest (about 0.300 liters
is average for a 12 to 13 year old).
A spirometer can tell a doctor how far a respiratory disease has
progressed and help determine what the treatment should be (See
Hazards). One of the more common breathing problems in children
is asthma, an allergy disease that causes chronic
inflammation and swelling of the bronchial tubes. This
limits the amount of air that a person can breathe in and out at a given
A healthy lung
How do we know how lungs
Sometimes the best way to
find out how something works is to take it apart and figure out what the
smaller parts do. That's exactly what scientists have done to learn about
the lungs. Some people donate their bodies to medical schools after
they die, so that doctors can study the parts and try to figure out how
they work. Animal studies have also been used to learn about the
lungs. Scientists look closely at all of the different parts of
the lung including the alveoli, bronchiole, bronchial tubes, membrane
linings, and the different lobes of the lung.
|In living people,
can view the inside of the lung using a fiber optic camera, called an
endoscope. Using an endoscope, physicians can observe the lung while
it is moving and observe very closely the changes that take place during
Scientists have also learned about the gas
exchange that takes place in the lungs by sampling the air directly. They
have learned what makes up inspired air
and how it differs from air deep
within the lungs. For example, they have learned that when air enters
the lung it is greatly humidified in order to facilitate gas exchange.
In order to do this, the lung makes the air a bit "thicker" and
causes it to stay in
the lungs longer, increasing contact time and gas exchange. This is the
reason that it is sometimes easier to breathe in a room with a humidifier.
Inside of a trachea as seen in an endoscopy
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