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The Respiratory System
Why do you need to breathe?
All the cells in your body require oxygen. Without it, they couldn't move, build,
reproduce, and turn food into energy. In fact, without oxygen, they and you would die!
How do you get oxygen? You get oxygen from breathing in air which your blood
circulates to all parts of the body.
How do you breathe?
You breathe with the help of your diaphragm and other muscles in your chest and
abdomen. These muscles literally change the space and pressure inside your body to
accomodate breathing. When your diaphragm pulls down, it not only leaves more space
for the lungs to expand but also lowers the internal air pressure. Outside, where the air
pressure is greater, you suck in air in an inhale. The air then expands your lungs like a
pair of balloons. When your diaphragm relaxes, the cavity inside your body gets smaller
again. Your muscles squeeze your rib cage and your lungs begin to collapse as the air is
pushed up and out your body in an exhale.
So, it all starts at the nose?
Yup. About 20 times a minute, you breathe in. When you do, you inhale air and pass it
through your nasal passages where the air is filtered, heated, moistened and enters the
back of the throat. Interestingly enough, it's the esophagus or foodpipe which is located at
the back of the throat and the windpipe for air which is located at the front. When we eat,
a flap -- the epiglottis -- flops down to cover the windpipe so that food doesn't go down
the windpipe.
So -- back to breathing -- the air has a long journey to get to your lungs. It flows down
through the windpipe, past the voice box or vocal cords, to where the lowermost ribs
meet the center of your chest. There, your windpipe divides into two tubes which lead to
the two lungs which fill most of your ribcage. Inside each of your sponge-like lungs,
tubes, called bronchi, branch into even smaller tubes much like the branches of a tree. At
the end of these tubes are millions of tiny bubbles or sacs called aleoli. Spread out flat, all
the air sacs in the lungs of an adult would cover an area about the third of a tennis court.
What do these sacs do?
They help perform an incredible magic act. Your air sacs bring new oxygen from air
you've breathed to your bloodstream. They exchange it for waste products, like carbon
dioxide, which the cells in your body have made and can't use.
How does this exchange work?
This exchange works with the help of the red blood cells in your bloodstream. Your red
blood cells are like box cars on train tracks. They show up at the sacs at just the right
time, ready to trade in old carbon dioxide that your body's cells have made for some new
oxygen you've just breathed in. In the process, these red blood cells turn from purple to
that beautiful red color as they start carrying the oxygen to all the cells in your body.
But what happens to the carbon dioxide?
It goes through the lungs, back up your windpipe and out with every exhale. It's a
remarkable feat, this chemical exchange and breathing in and out. You don't have to tell
your lungs to keep working. Your brain does it automatically for you.
Factoids
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Your lungs contain almost 1500 miles of airways and over 300 million alveoli.
Every minute you breathe in 13 pints of air.
Plants are our partners in breathing. We breathe in air, use the oxygen in it, and
release carbon dioxide. Plants take in carbon dioxide and release oxygen. Thank
goodness!
People tend to get more colds in the winter because we're indoors more often and in close
proximity to other people. When people sneeze, cough and even breathe -- germs go
flying!
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4.
Why do we need to breathe?
What role does your diaphragm play in breathing?
What keeps food from going down our windpipe?
Spread out flat, about how much space would all the airsacs in the lungs of an
adult cover?
5.
What role do red blood cells play in respiration?
6.
Every minute about how much air do you breathe in?
7.
How are plants our partners in breathing?
The Lungs
Lungs are an important aspect of breathing by providing a place for the exchange of
gases between blood and air. The lungs are cone shaped and connected to the respiratory
tract by the primary bronchi, which are attached to the trachea, or windpipe. The lungs
are covered in protective membranes called the pulmonary plurae, and a fluid filled space
between the membranes called the pleural cavity.
1.
2.
Lungs provide a place for what important aspect of breathing?
What are pleurae?
Respiratory System: Oxygen Delivery System
The primary function of the respiratory system is to supply the blood with oxygen in
order for the blood to deliver oxygen to all parts of the body. The respiratory system does
this through breathing. When we breathe, we inhale oxygen and exhale carbon dioxide.
This exchange of gases is the respiratory system's means of getting oxygen to the blood.
Respiration is achieved through the mouth, nose, trachea, lungs, and diaphragm. Oxygen
enters the respiratory system through the mouth and the nose. The oxygen then passes
through the larynx (where speech sounds are produced) and the trachea which is a tube
that enters the chest cavity. In the chest cavity, the trachea splits into two smaller tubes
called the bronchi. Each bronchus then divides again forming the bronchial tubes. The
bronchial tubes lead directly into the lungs where they divide into many smaller tubes
which connect to tiny sacs called alveoli. The average adult's lungs contain about 600
million of these spongy, air-filled sacs that are surrounded by capillaries. The inhaled
oxygen passes into the alveoli and then diffuses through the capillaries into the arterial
blood. Meanwhile, the waste-rich blood from the veins releases its carbon dioxide into
the alveoli. The carbon dioxide follows the same path out of the lungs when you exhale.
The diaphragm's job is to help pump the carbon dioxide out of the lungs and pull the
oxygen into the lungs. The diaphragm is a sheet of muscles that lies across the bottom of
the chest cavity. As the diaphragm contracts and relaxes, breathing takes place. When the
diaphragm contracts, oxygen is pulled into the lungs. When the diaphragm relaxes,
carbon dioxide is pumped out of the lungs.
1.
What is the job of your diaphragm?
Inspiration
How is it possible to get air inside of our bodies?
If I want to get air inside a room, I would have to do a few things. First of all, I'd have
to have a passageway for the air-- like an open door or window. Then I would need some
force to push or draw the air into the room. The air could be pushed into the room from
outside. For example, a fan located in the hall outside of the room could be used to push
the air into the room through the door, or the wind outside could push air into the room
through the window. The air could also be drawn into the room from inside. For
example, a fan could be positioned in front of the window inside the room, and draw air
in through the window.
Well, in our bodies, we have a clear passageway for the air, from outside into our nasal
cavity (or mouth), to our pharynx, trachea, bronchi, bronchioles, and eventually into the
alveoli. We have to get the air into our alveoli, because that is where all gas exchange
will occur.
The other thing we need is a way to push or draw air into that passageway. We can't
sit in front of a fan all day! We certainly have no way to push it in (or you'd see
something outside of our noses all day), so there has to be a way to draw it in. You may
now be thinking about how something could act like a fan within our bodies, drawing air
into our alveoli... at least I hope that is what you are thinking. It works something like
that.
Think back to the fan example. A fan is a force on the air. When it forces the air to
move, we can talk about the fan increasing the air pressure on the air it moves. So, what
we really need is a way to create air pressure to draw the air into our bodies. Right?
The air in our world sits at a rather constant pressure, called the atmospheric
pressure, of 760 mm Hg. Note that air pressure, just like blood pressure, is measured in
units of "mm Hg." If we want to draw air into our bodies, we have to be able to make our
respiratory tract have a lower pressure than 760 mm Hg. It has to be lower, because all
items tend to move from high pressure toward low pressure without any extra energy
needed.
Therefore, the entire question of how we inhale can be narrowed down to the more
specific question: "how do we decrease the pressure within our respiratory tract?" Keep
in mind that we have to do this over and over, since breathing is cyclical.
How do we decrease the pressure within our respiratory tract?
To understand this, you may need to picture what air pressure really is. Air is made up
of many molecules. All molecules are in constant, random motion. As the molecules
move around, the amount that they bang against each other and against any container that
they are in is their pressure. I have tried to demonstrate this for you in the animation
below.
At first, the air molecules are just moving around normally. Notice that their
movement is pretty random (at least I tried to make it random). Then, I have gone ahead
and changed the container within which they are moving. I made the container larger.
Once the container is larger, the molecules, still moving at the same rate, are now less
likely to bump into each other or into the walls of the container. You should at least be
able to see that the air molecules tend to be more spread out when the container is larger.
Less bumping around of air molecules reflects less pressure of the air.
This is the trick, then. In order to decrease the pressure within our respiratory tract, we
have to expand our container. Our container is basically our thorax. If we can expand
our thorax, the air pressure within our thoracic cavity will fall, and air will rush into our
respiratory tract.
Expiration
For the most part, we exhale passively. That means that we don't have to expend any
energy to exhale. You see, when our diaphragm has stopped contracting for inspiration,
it can now begin to relax. And the abdomen is under higher pressure when the
diaphragm is contracted (because the thorax expanded downward). Therefore, the
thoracic volume is restored by simple elastic recoil of the diaphragm. Any other muscles
that were active to cause inspiration are simply shut off so that they relax for expiration.
We do have to be able to voluntarily exhale in order to speak, whistle, play a wind
instrument, blow up a balloon, etc. So, there are muscles that contract for voluntary
expiration. The major muscles involved are the internal intercostal muscles and
abdominal wall muscles that constrict the abdomen like the internal and external
obliques and the rectus abdominis muscles. The internal intercostal muscles lower and
constrict the rib cage to decrease thoracic volume, while the abdominal wall muscles
cause constriction of the abdomen, forcing the abdomen to push against the diaphragm,
shoving it back upward into the thorax.
1.
2.
What is inspiration?
What is expiration?
Amazing Respiratory System Facts
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The right lung is slightly larger than the left.
Hairs in the nose help to clean the air we breathe as well as warming it.
The highest recorded "sneeze speed" is 165 km per hour.
The surface area of the lungs is roughly the same size as a tennis court.
The capillaries in the lungs would extend 1,600 kilometres if placed end to end.
We lose half a litre of water a day through breathing. This is the water vapour we
see when we breathe onto glass.
A person at rest usually breathes between 12 and 15 times a minute.
The breathing rate is faster in children and women than in men.
1. Which lung is bigger--your right or your left?
2. What is the highest recorded sneeze speed?
3. About how much water do we lose per day through breathing?