The Respiratory System

Why do you need to breathe? All of the cells in the body require oxygen.  Without it, they couldn't move, build, reproduce, and turn food into energy.  Your body gets oxygen from breathing in air which circulates to all parts of the body.

This chart of the respiratory system shows the apparatus for breathing.  Breathing is the process by which oxygen from the air is brought into the lungs and circulated throughout the body in the blood.   At the same time,  the blood gives up waste matter, also called carbon dioxide, which is transported out of the lungs as we breathe out.

Important Vocabulary:

Nasal cavity (nose):  the preferred entrance for outside air into the respiratory system

Oral cavity (mouth):  air also enters the body here

Adenoids:  lymph tissue at the top of the throat that helps resist body infection

Tonsils:  lymph nodes in the wall of the pharynx that are often removed when infected

Pharynx (throat):  catches incoming air from the nose and passes it downward to the windpipe

Epiglottis:  a flap of tissue that guards the entrance to the trachea

Larynx (voice box):  contains the vocal cords

Esophagus:  the passage leading form the mouth and throat to the stomach

Trachea (windpipe):  the passage leading from the pharynx to the lungs   trachea

Ribs:  bones supporting and protecting the chest cavity

Bronchi (tubes):  trachea divides into these two main tubes, one for each lung

Cilia:  the bronchial tubes are lined with these very small hairs that have a wave-like motion

Mucus:  the movement of the cilia carries mucus upward into the throat where it is coughed up or swallowed

Diaphragm:  wall of musle that separates the chest cavity from the abdominal cavity

Alveoli:  small sacs where air goes when breathed in

Capillaries:  blood vessels

Pulmonary Artery / Vein:  blood is carried to the capillaries by the pulmonary artery and taken away by the pulmonary vein

**Image from
**Vocabulary adapted from http://

Pretend you are a volunteer going off to war.  In order to be admitted into the army, you must first pass a physical fitness examination.  Although you must complete various portions of the test before you leave, we are focusing on respiration rates today.  Begin by using a stop watch and counting your resting respiration rate.  This can be done by counting how many times you breathe in a minute.  Record your data in the chart below.  Next, run in place for one minute.  As soon as you are done, count how many times you breathe in a minute.  Record this number on the table.  Finally, run in place for three minutes at a fatser pace.  When you finish, count how many times you breathe in a minute.  Record this number below.  Work with your assigned partner to complete the activity.

Respiratory Rate Table:

Partner One
Partner Two
Resting Rate

Breathing after 1 minute

Breathing after 3 minutes

1.  What did you find about your breathing rate as you began to run?  Did your respiration rate increase or decrease?  Why do you think this occurred?

2.  What was your physical reaction to the running?  How did your heart and lungs respond?

3.  Do you have any insights as to why respiration was affected when you ran compared to when you were at rest?

When we exercise, our muscles are using up a lot of energy and our cells need to get more energy out of the food we've eaten.  This takes lots of oxygen, so our lungs breathe in and out faster to get more oxygen out of the air.  They in turn produce more carbon dioxide, so the waste must be exhaled.  When we are resting, our cells are not working as hard, so less energy is used and our breathing can slow down.  

You have probably noticed that when you are exercising, your heart beats more quickly.  This occurs so that the blood can carry oxygen to the cells faster.  Your heart and lungs work together to make sure every cell in your body receives the right amount of oxygen.

When you rest, your cells aren't working hard, so they require less oxygen to function.  In addition, they produce less carbon dioxide.  As a result, you do not have to breathe as often as when you are moving.  Because your heart and lungs work as a team, when your lungs are not working hard, neither is your heart!

**Information adapted from

To find out how a mammal's respiratory system works, go to               

Image from

Let's watch what the body looks like while a person is breathing.  Go to the site
to explore the workings of the human respiratory system from an inside perspective.

Frequently Asked Questions:

Why Do I Yawn?
     When you are sleepy or drowsy the lungs do not take enough oxygen from the air. This causes a shortage of oxygen in our bodies. The brain senses this shortage of oxygen and sends a message that causes you to take a deep long breath---a YAWN.

Why Do I Sneeze?
     Sneezing is like a cough in the upper breathing passages. It is the body's way of removing an irritant from the sensitive mucous membranes of the nose. Many things can irritate the mucous membranes. Dust, pollen, pepper or even a cold blast of air are just some of the many things that may cause you to sneeze.

What Causes Hiccups?
    Hiccups are the sudden movements of the diaphragm. It is involuntary --- you have no control over hiccups, as you well know. There are many causes of hiccups. The diaphragm may get irritated, you may have eaten to fast, or maybe some substance in the blood could even have brought on the hiccups.
**Questions and Answers found at

**Images from

Back to Process Page

**Activity page created by Nicki Gannon