Why Do Humans Need To Breathe: The Human Respiratory System

submitted by: Joshua P

last updated: 10/3/11

Breathing: How we do it

When we breathe in, the muscles between our ribs contract and causes the chest to expand. The lungs inflate with oxygen until the air pressure inside of the body is the same as the air outside. We then exhale, forcing the air out of our body. We do not blow out all of our air because the blood is constantly carrying oxygen throughout out blood stream to keep us alive. The diaphragm is a breathing muscle that only mammals have. We need to breathe in to get oxygen. The brain is in control of our breathing. It tells the diaphragm to move up and down. It also tells the muscles to move in and out, as mentioned before.

This is my diagram of how we breathe

Why we need Oxygen over other things:

Once we get oxygen in our body, it can break down food into energy. We use this energy to keep us moving and to keep ourselves warm. After oxygen turns food into energy, the oxygen becomes carbon dioxide. We must breathe out carbon dioxide because it is not safe for inhaling. Plants and trees can take in carbon dioxide and turn it back into oxygen.

Our many different parts to the respiratory system:

There are many different parts to our respiratory system. There is the nose, throat, windpipe, voice box, bronchi, and lungs. The heart and bloodstream come in later as well.

The short process of breathing:

Air enters our body through the nose and continues into a hollow space behind the nose. It also sometimes enters through the mouth, even though it is not as good of a place to get air as the nose. These airways meet at the pharynx (the upper part of the throat). From the throat, to long passages open up downward. One is the esophagus, which is for food to go down into the stomach. The other is the passage for air. The top of the air passage contains the larynx, or the voice box. The rest of it is the trachea, or the windpipe. The windpipe then separates into two bronchi, or branches. There is one branch for each lung. Once inside the lungs, the branches keep separating into smaller and smaller branches which are covered with alveoli, or tiny air sacks. The alveoli contain tiny blood cells called capillaries. When we breathe in and the air fills our lungs, the blood in our capillaries starts to soak it up. The blood then is taken through the blood stream to all parts of our body. When blood picks up oxygen it also brings the carbon dioxide back up to the lungs. We then breathe it out and repeat the process over again.

Problems with the respiratory system:

Hiccups are a harmless problem that can happen to the respiratory system. They are caused when the diaphragm makes quick, jerky movements. Colds and the flu start up in the nose and in the throat. They are mostly not harmful infections. Pneumonia is a harmful infection of the lungs. Lung cancer, emphysema, and tuberculosis are serious diseases of the lungs. These can end in death.


Respiratory system- our system of breathing.

Diaphragm- a breathing muscle that only mammals have.

Bronchi- small branches that carry oxygen down into the lungs.

Pharynx- the upper part of the throat.

Larynx- the voice box.

Trachea- the windpipe.

Capillaries- essentially small storage containers for blood inside of the alveoli.

Tuberculosis- a very harmful sickness to the lungs.


"Respiratory System." Britannica Elementary Encyclopedia. Encyclopædia Britannica Online School Edition.Encyclopædia Britannica, Inc., 2011. Web. 28 Sept. 2011.

Bosch Roca, Nuria. The respiratory system. New York, Chelsea House Publishers: 1996. Print.

Kittredge, Mary. The respiratory system. New York, Chelsea House: 1988. Print.

Whittemore, Susan. The respiratory system. Philadelphia, Chelsea House Publishers: 2004. Print.

Here is a close up of the starting point for our respiratory system.