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Respiratory System

Respiration happens when we use the air we breathe in to make energy. We all know we need our nose and mouth for breathing. But there are a lot more organs involved in respiration. These organs form our respiratory system!

Picture of a woman breathing.

Parts of the Respiratory System

Many different organs are used for respiration.

The anatomy of the respiratory system

The anatomy of the respiratory system


This is where air enters out bodies. Have you noticed how hairy our nostrils are? These hairs actually catch dirt and dust particles and  clean the air we breathe! Our nostrils are also lined with ciliated cells, which have hair-like cilia on them. Cilia beat back and forth to bring up mucus. When we blow our noses, the snot that comes out is made up of this mucus and the dirt particles.


Most of the air we breathe comes through our nose. But, we can also breathe through our mouths to get more air!


The pharynx, or throat, is part of the passage (or tube!) that air will go down to enter our lungs.


The voice box, another part of our main air passage.


The windpipe is a long tube that goes down our neck to the lungs. There is also cilia in the windpipe. The windpipe’s lining makes mucus, which traps dust and other dirt particles. Cilia brings this mucus towards our throat, where we swallow and digest it.

Bronchi and Bronchioles

Tubes that branch from the trachea into our lungs. The bronchioles make a tree-like structure in the lungs so air can reach every corner.


Two spongy organs in our chest. Lungs have a lot of little air sacs called alveoli. Tiny blood capillaries run through alveoli. When air reaches the alveoli, it passes into the bloodstream. It is then carried around our entire bodies.


The main muscle in the respiratory system. The diaphragm stretches out underneath the lungs. When it contracts, it expands outwards. This makes more space inside our chest for air to rush in. When the diaphragm relaxes, it moves inwards. This decreases the space inside our chest and pushes air out.

Respiration Process

Respiration involves two things: inhaling and exhaling. Inhaling just means breathing in, and exhaling is just breathing out.

When we inhale, the diaphragm contracts. Air rushes in through our nose and mouth into the main air passage. Air goes down through the pharynx, the larynx, and then the trachea. The bronchi split the air between our two lungs. Air then reaches the alveoli and passes through its walls to the bloodstream.

How gas exchange in the cells works.

How gas exchange in the cells works.

Once air enters the bloodstream, red blood cells carry it all around our body. Our bodies only use oxygen for respiration. During respiration, oxygen and glucose from our food break down. They then release energy, carbon dioxide, and water vapor. Here is the chemical equation of respiration: C6H12O6 + 6O2 → 6CO2 + 6H2O + energy. In the equation, C6H12O6 is glucose, O2 is oxygen, CO2 is carbon dioxide, and H2O is water.

Once our cells are done, they release carbon dioxide and water back into the bloodstream. Red blood cells pick them up and carry them back to the lungs. Carbon dioxide passes from our blood vessels into the lungs. The diaphragm relaxes, the space inside our chests gets smaller, and we exhale. This is how the respiratory system works!

Alveoli in our lungs

Alveoli in our lungs

As a bonus feature, notice how in the picture, the blood capillaries around the alveoli are red and blue. This is because oxygen rich blood is often drawn as red, and carbon dioxide filled blood is shown as blue. Our blood can’t actually be blue, but blood with more carbon dioxide in it tends to be darker in color!

Types of Respiration

There are two types of respiration: aerobic and anaerobic. Aerobic respiration means respiration when there is air. This is the type of respiration that living organisms use most of the time, and the one we need to live.

Anaerobic respiration happens when there is no air around, but we still need to make energy! In anaerobic respiration, glucose is converted to lactic acid. This is then used to release energy for the body. Have you ever exercised too hard and haven’t been able to breathe properly? If so, you might remember feeling a kind of burning in your sides. This burning feeling actually comes from the build-up of lactic acid in your cells!

When we exercise too hard, sometimes we feel burning pain in our sides.

When we exercise too hard, sometimes we feel burning pain in our sides.

Here is the equation for anaerobic respiration: C6H12O6 → 2C3H6O3. In the equation, lactic acid is C3H6O3. Compare this equation with the previous equation for aerobic respiration. Notice how in anaerobic respiration, O2 (or oxygen) is not present. This means there is no air involved in the use of glucose to make energy. In fact, we almost don’t need the respiratory for anaerobic respiration!

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Written by: Minh Nguyen