Fishy Origin
Modern mammalian lungs evolved from the air-breathing organs, that developed in fish, about 400 million years ago.
In this limitless world, our throat is like a swinging door. The air comes in and goes out like someone passing through a swinging door. If you think, 'I breathe', the 'I' is extra. There is no you to say 'I'. What we call 'I' is just a swinging door which moves when we inhale and when we exhale. It just moves; that is all. When your mind is pure and calm enough to follow this movement, there is nothing: no 'I', no world, no mind nor body; just a swinging door. - Shunryu Suzuki (Beginner's Mind)

Life is a ceaseless rhythmic symphony, played with the lead instruments being the breathing lungs and the thudding heart. As Shunryu Suzuki, the great Zen master said, we are all swinging doors, through which air enters, enriching the body with oxygen and leaves, cleansing it of carbon dioxide. Almost all life owes its existence to some form of air exchange mechanism, that filters out oxygen from the atmosphere, to power cellular energy-generating processes.

Amazing Facts About the Respiratory System

Our respiratory system is one of the most sophisticated biological mechanisms in nature, designed to enable the most important life process of aerobic cellular respiration, which helps our body produce energy, from food. It achieves this through the supply of Oxygen and removal of Carbon Dioxide.

Respiratory system facts

Respiratory System Structure

Human respiratory system

The entire respiratory system is made up of many parts, including the nose, mouth, voice box (larynx), the wind pipe (trachea), bronchial tubes, lungs, the diaphragm, along with the neck, abdominal, and intercostal muscles that enable breathing.

When air passes through the nose and into the nasal passage (the windpipe), it gets filtered, moistened, and heated.

The walls of the respiratory airway, are lined with tiny hair, covered with mucous, that help trap foreign particles and filter out the inhaled air. These particles may later be expelled through cleansing events like a sneeze.

Sneeze velocity

To prevent the entry of food and other liquids in the wind pipe, it is covered by the epiglottis, a thin layer of tissue. It stays open during breathing, but closes the wind pipe while swallowing food.

Lungs are dense networks of connected tubules, that transport oxygen from air to nourish the trillions of cells in our body. They are each made up of five lobes.

The right lung is slightly larger than the left one. The reason for this is attributed to be the left placing of the heart.

Here's a fun fact. The surface area of lungs, including the airways and the millions of alveoli amounts to about 70 to 100 square meters, which turns out to be almost the same size as a tennis court.

Gas exchange process

The air breathed in, is taken through increasingly minute tubes to about 300 to 600 million minuscule air bags called the alveoli, with walls that are almost 0.2 micrometer thin. They are the places where oxygen and carbon dioxide are exchanged with minute blood capillaries through diffusion.

When you take a deep breath, air enters your lungs and your chest expands. Your lungs sift oxygen through the air and diffuse it into your blood, from where it is supplied to various cells of your body.

Carbon dioxide generated in the cells, as a byproduct of aerobic respiration, is brought to the capillaries in the lungs, by red blood cells. When you exhale, the carbon dioxide is expelled out by the lungs.

A type of capillary, pulmonary venules carry oxygenated blood towards the heart.

Another type of capillary, the pulmonary arterioles carry deoxygenated blood from the heart, to the lung, for oxygenation.

Thus, with every breath taken in, the blood is purified with oxygen and with every exhaled breath, waste products like carbon dioxide are exhaled out with water vapor. This in short, is what happens during every 'breathe in-breathe out' respiratory cycle.

If the airways in the lung were laid out, they would cover a total distance of 1500 miles.

Breathing is initiated by the diaphragm, which is a stretchable muscle under the lungs. When it contracts, the volume of the chest cavity rises and the air pressure drops. That is what enables the high pressure air outside, to enter the lungs and makes them expand like balloons.

Diaphragm action

When the diaphragm expands, volume of the lung cavity decreases, leading to an increase in air pressure, which leads to exhalation. Thus, it is the diaphragm that facilitates the rising and falling of the chest during respiration.

Ibn al-Nafis, a 13th century Arab physician, was the first to describe what is now known as pulmonary circulation of blood, the process of oxygen and carbon dioxide exchange that occurs in the lungs.

Toronto-based thoracic surgeon, Joel D. Cooper performed the first successful single lung transplant in 1983, as well as the first double lung transplant in 1986.

The unity of ancient Egypt's upper and lower lands was pictured through a hieroglyph, that showed lungs, connected with a wind pipe.


Every minute we breathe, we take in about 17.22 pints (8.15 liters) of air.

Every person takes about an average of 16 breaths per minute, 960 per hour, 23,040 a day, 8.4 million per year, and 672.768 million, over a lifetime of 80 years.

Through every breath, we take in about half a liter of air.

Newborn babies can take about 30 to 60 breaths per minute, up to 6 weeks after birth.

During heavy exercise, a person may take as many as 45 breaths per minute.

In a day, the lungs transport about 300 cubic feet of air (which is about 8.5 cubic meters of air).

Human breathing mechanism is called tidal breathing, as air comes out the same way it goes in.

We exhale about half a liter of water vapor in a whole day. About 17.5 ml of water is expelled every hour, through exhalation. The body tends to lose more of it, during heavy exercise or a strenuous activity.

Due to the blood-acidifying effect of carbon dioxide, an average human adult can hold his breath for only up to 30 to 60 seconds. However, deep sea divers have been known to hold their breaths for as long as 22 minutes.

A sneeze is the respiratory system's protective reflex mechanism for cleaning irritants from the mucous membrane, situated in the interior of the nose. Pepper and pollen are some of the most common irritants.

Contrary to popular assumptions, the speed of air particles rushing out during a sneeze is not around 100 miles per hour, but only about 16.2 Km/hr (4.5 m/sec).

Since a lung is the only organ that can float on water, when filled with air, it is used when conducting an autopsy, to ascertain whether a baby was stillborn. If the lung happens to stay afloat in water, it can be deduced that the baby was definitely born alive.

Diseases and Disorders of the Respiratory System

People with asthma have difficulty in breathing because the air tubes in their lungs (bronchi and bronchioles) become narrow and constricted due to inflammation, causing a reduction in the amount of oxygen supplied to the lungs.

More than 24 million Americans suffer from Chronic Obstructive Pulmonary Disease (COPD) is, which is an umbrella term for all respiratory diseases that lead to breathlessness. In 2009, it was the third leading cause of death in USA.

Common cold, the most rampant respiratory system infection, is caused by 200 different types of viruses.

It is known that smoking in teens can cause the growth of lungs to stunt. It also causes diseases and disorders including oral cavity cancer, larynx cancer, esophagus cancer, lung cancer, bladder cancer, heart attack, and emphysema.

All over the world, about 1.4 million people are diagnosed with lung cancer every year.

Hope these facts have aroused your curiosity about the intricate workings of the human body. It is great to know what all it takes to make every single breath possible. Make sure that you make it count.