ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

Human Breathing System – Human Respiratory System – and Why Do We Breathe?

Updated on December 18, 2011

Why We Breathe

Why do we breathe? We breathe so that we can live. To live, we constantly need a supply of energy to our body cells. To have energy, we need to eat food with carbohydrates. To have energy, we need to digest carbohydrates to glucose (sugar). To have energy, we need to convert glucose to energy. To convert glucose to energy, we need to burn glucose with oxygen in our bodies to release the energy to the cells. To have oxygen, we need to inhale oxygen when we breathe in. The equation for this process is as follows:

Glucose + Oxygen → Energy + Carbon dioxide + Water

This equation is called aerobic respiration equation. This process of aerobic respiration takes place in a section of a cell called mitochondria.

Aerobic Respiration

From the aerobic respiration equation, when glucose is burned using oxygen to release energy there are two waste products produced. These two wastes are carbon dioxide and water. These two wastes are called metabolic wastes. These wastes will diffuse out of the cells and into the blood before diffusing out of the blood to be exhaled. These wastes of carbon dioxide and water are exhaled as carbon dioxide gas and water vapour when we breathe out.

So, why do we breathe? We breathe in to inhale oxygen which is used to burn food into energy for our body cells. We breathe out to exhale out carbon dioxide gas and water vapour which are waste products when food is converted into energy for our body cells. Without energy for our body cells we can not live.

Main Parts of Human Breathing System

The five principle parts of a human respiratory system are:
1. Nose
2. Trachea, also known as wind-pipe
3. Bronchi
4. Lungs
5. Diaphragm

Parts of a human respiratory system. Image Credit: LadyofHats via Wikimedia Commons.
Parts of a human respiratory system. Image Credit: LadyofHats via Wikimedia Commons. | Source

1. Nose

The Nose is that part on the face in humans that contains two nostrils. The nose contains the organs of smell and functions as the usual passageway for air in the breathing process. In the Human Respiratory process, air from the atmosphere will enter the nose. In the nose, air is cleaned, warmed and moistened. The nose has tiny hairs and mucus for trapping germs and dust contained in the air.

Nasal Cavity is therefore defined as a system of chambers with mucus membrane through which air passes from the nostrils to the pharynx. During the breathing in process, air is filtered, warmed, moistened, and smelled. Pharynx is a hollow tube about 10 cm long that starts behind the nose and ends at the top of the trachea (windpipe). If you were to breathe through the mouth, air would enter the pharynx.

2. Trachea – Windpipe

Another name for trachea is the windpipe. The trachea is a wide pipe which is kept open by C-shaped rings of tough tissue. It’s the passageway through which air passes. The trachea has mucus membrane for trapping dust and germs and moving them towards pharynx.

We can define larynx as the voice box. In humans, it’s that hollow muscular organ with vocal cords for air passage. When air passes over larynx, it vibrates.

And we define epiglottis as an elastic flap that covers the trachea during swallowing, at the root of the tongue, so that food does not enter the windpipe.

3. Bronchi

As the trachea approaches the lungs it subdivides into two branches. Each branch is called a bronchus. Plural of bronchus is bronchi. Each bronchus joins a separate lung. The bronchi are lined with mucus membranes for trapping dust and microscopic particles such as germs. The bronchi are also kept open by C-shaped rings of tough tissue.

As the bronchi extend further into the lungs they subdivide into many smaller tubes called bronchioles. The bronchioles are to be found inside the lungs. Bronchioles do not have the C-shaped rings of tough tissue, but they are just tubes. The bronchioles are also lined with mucus membranes for trapping off dust and germs from the air.

4. Lungs

Human have a pair of lungs situated within the rib cage called a chest. There is a lung on each side of the chest, left and right. The bronchioles inside the lungs divides into millions of fine tubes that lead to air sacs called Alveoli. The air sacs have capillaries that allow gas exchange. During the exchange of gas in the air sacs, oxygen is absorbed by the blood whilst at the same time the blood gives out carbon dioxide. This is called Diffusion of gases between the air surrounding the alveoli.

5. Diaphragm

The diaphragm is a dome-shaped, muscular partition separating the chest (thorax) from the abdomen. Contraction and retraction of the diaphragm will increase or decrease the volume of the chest thus inflating and deflating the lungs as follows:

a) When the diaphragm moves downwards, the volume of the chest will increase and the lungs will expand sucking in air. This is called breathing in - inhalation.

b) When the diaphragm moves upwards, the volume of the chest will decrease and the lungs will contract expelling out air. This is called breathing out - exhalation.

If you have liked this article, and you would want this page to keep up and improved, you can help in any way you can. A free way to help would be to link back to this webpage from your web page, blog, or discussion forums.

The Author’s page is designed to help beginners and average readers make some money as an extra income to supplement what they may be earning elsewhere - details of which you can find in My Page, if you will.


    0 of 8192 characters used
    Post Comment

    • RK Sangha profile image

      RK Sangha 

      6 years ago from USA

      Thanks for a very good hub.

    • Hello, hello, profile image

      Hello, hello, 

      6 years ago from London, UK

      Thank you for your comprehensive and detailed hub. It fascinating and interesting.

    • Rising Caren profile image

      Rising Caren 

      6 years ago from New York

      It is amazing just how complex our bodies are and how much we take it for granted.

      PS. The thing about long articles, it's easier to make mistakes. I caught one "two lung".

    • parrster profile image

      Richard Parr 

      6 years ago from Australia

      Thanks for taking the time to write this, the human body is truly fascinating in its design. Voted up and useful

    • parrster profile image

      Richard Parr 

      6 years ago from Australia

      Thanks for taking the time to write this, the human body is truly fascinating in its design. Voted up and useful

    • molometer profile image


      6 years ago from United Kingdom

      Very interesting. This vital system is so fascinating.


    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

    Show Details
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)