Answer Posted / mike

The Respiratory System is a Oxygen Delivery System

The primary function of the respiratory system is to supply
oxygen to the blood system 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 I
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.
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? 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?
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
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!

Welcome to the Respiratory System




All animals need oxygen to live. Land animals get
oxygen from the air. Without the oxygen in the air we
cannot survive more than a few minutes. Breathing happens
automatically, we do not have to even think about it.
We breathe in order to take oxygen into our bodies and get
rid of carbon dioxide. The oxygen is carried in the blood
to all the body's cells. The air we breath out has 100
times more carbon dioxide than the air we breath in.
The SINUSES are hollow spaces in the bones of the head.
Small openings connect them to the nasal cavity. The
functions they serve are not clearly understood, but
include helping to regulate the temperature and humidity of
air breathed in, as well as to lighten the bone structure
of the head and to give resonance to the voice.
The NASAL CAVITY (nose) is the preferred entrance for
outside air into the Respiratory System. The hairs that
line the inside wall are part of the air-cleansing system.
Air also enters through the ORAL CAVITY (mouth), especially
in people who have a mouth-breathing habit or whose nasal
passages may be temporarily obstructed, as by a cold.
The ADENOIDS are overgrown lymph tissue at the top of the
throat. When they interfere with breathing, they are
generally removed. The lymph system, consisting of nodes
(knots of cells) and connecting vessels, carries fluid
throughout the body. This system helps resist body
infection by filtering out foreign matter, including germs,
and producing cells (lymphocytes) to fight them.
The TONSILS are lymph nodes in the wall of the pharynx that
often become infected. They are an unimportant part of the
germ-fighting system of the body. When infected, they are
generally removed.
The PHARYNX (throat) collects incoming air from the nose
and passes it downward to the trachea (windpipe).
The EPIGLOTTIS is a flap of tissue that guards the entrance
to the trachea, closing when anything is swallowed that
should go into the esophagus and stomach.
The LARYNX (voice box) contains the vocal cords. It is the
place where moving air being breathed in and out creates
voice sounds.
The ESOPHAGUS is the passage leading from the mouth and
throat to the stomach.
The TRACHEA (windpipe) is the passage leading from the
pharynx to the lungs.
The RIBS are bones supporting and protecting the chest
cavity. They move to a limited degree, helping the lungs to
expand and contract.
The trachea divides into the two main BRONCHI (tubes), one
for each lung. These, in turn, subdivide further into
bronchioles.
The RIGHT LUNG is divided into three LOBES, or sections.
The left lung is divided into two LOBES.
The PLEURA are the two membranes, that surround each lobe
of the lungs and separate the lungs from the chest wall.
The bronchial tubes are lined with CILIA (like very small
hairs) that have a wave-like motion. This motion carries
MUCUS (sticky phlegm or liquid) upward and out into the
throat, where it is either coughed up or swallowed. The
mucus catches and holds much of the dust, germs, and other
unwanted matter that has invaded the lungs and thus gets
rid of it.
The DIAPHRAGM is the strong wall of muscle that separates
the chest cavity from the abdominal cavity. By moving
downward, it creates suction to draw in air and expand the
lungs.
The smallest subdivisions of the bronchi are called
BRONCHIOLES, at the end of which are the alveoli (plural of
alveolus).
The ALVEOLI are the very small air sacs that are the
destination of air breathed in. The CAPILLARIES are blood
vessels that are imbedded in the walls of the alveoli.
Blood passes through the capillaries, brought to them by
the PULMONARY ARTERY and taken away by the PULMONARY VEIN.
While in the capillaries the blood discharges carbon
dioxide into the alveoli and takes up oxygen from the air
in the alveoli.
Your respiratory system is dominated by your lungs. They
bring fresh oxygen (O2) into your body and expel carbon
dioxide (CO2). Oxygen travels from your lungs through the
bloodstream to the cells in all parts of your body. Cells
use the oxygen as fuel and give off carbon dioxide as waste
gas. The waste gas is carried by the bloodstream back to
the lungs to be exhaled.
The lungs accomplish this vital process - called gas
exchange - using an automatic and quickly adjusting control
system. This gas exchange process occurs in combination
with your central nervous system, blood circulatory system,
and your chest and diaphragm muscles.
In addition to gas exchange, your lungs and the other parts
of your respiratory system have other important jobs
related to breathing. These include:
Bringing all air to the proper body temperature.
Moisturizing the inhaled air for necessary humidity.
Protecting the body from harmful substances by coughing,
sneezing or filtering them, or by alerting the body through
your sense of smell.
Defending the lungs with cilia (tiny hair-like structures)
and mucus, which act to remove harmful substances deposited
in the respiratory system.
How your health is affected
Lung tissue cells can be injured directly by air pollutants
such as ground-level ozone, metals and free radicals. Ozone
can damage the alveoli ― the individual air sacs in the
lung where oxygen and carbon dioxide are exchanged.
Lung tissue has an abundant blood supply that can carry
toxic substances and their metabolites to distant organs.
In response to toxins, your lung cells also release a
variety of potent chemical mediators that may critically
affect the function of other organs such as those of the
cardiovascular system. This may also cause lung
inflammation and impair lung function.
Particulates
Deposition of inhaled particles within the lungs varies
widely depending on the particle size. Airway tissues that
are rich in bioactivation enzymes can transform organic
pollutants into reactive metabolites and cause secondary
lung injury.
Larger (coarse) particles in air pollution are more likely
to deposit in the upper airways of your lungs, and affect
this part of your lungs. Smaller (fine) particles penetrate
deeply into the alveolar region of the lungs and appear to
be able to affect more basic lung function. These effects
may be related to aspects of the chemistry or physical
nature of the particles.

Do you hav reference list?

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