Human Respiratory System: Definition and Features of Respiratory System (For CBSE, ICSE, IAS, NET, NRA 2022)

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Definition of Respiratory System

  • The organ system that involves inhaling of oxygen and exhaling of carbon dioxide to meet the energy requirements is known as Human Respiratory System.
  • It is a biological system consisting of specific organs and structures used for gas exchange in animals and plants.
  • The primary organs of the respiratory system are the lungs, which help in the exchange of gases.
    • Take in oxygen and expel carbon dioxide.
  • From the body՚s cells, the red blood cells collect carbon dioxide and transport it back to the lungs.
Human Respiratory System

Features of the Human Respiratory System

  • The energy is generated by the breaking down of the glucose molecules.
    • In all living cells of the human body.
  • Oxygen is inhaled and is transported to various parts.
    • Used in the process of burning food particles (breaking down of glucose molecules) .
  • At the cellular level in a series of chemical reactions.
  • The obtained glucose molecules are used for discharging energy in the form of ATP- adenosine triphosphate.
    • By the human body to fulfil essential life processes.

Different Parts of the Respiratory System

Parts of the Respiratory System


  • The nose and nasal cavity form the main external opening for the respiratory system.
  • The nose is a structure of the face made of:
    • Cartilage
    • Bone
    • Muscle and skin
  • The anterior portion of the nasal cavity is supported and protected.
  • The nasal cavity is a hollow space within the nose and skull.
  • The function of the nasal cavity:
    • To warm
    • Moisturize
    • Filter air entering the body before it reaches the lungs.


  • The framework for larynx is layed down by the two cartilaginous chords.
  • It is also termed as Adam՚s apple or the voice box.
  • Larynx generates sound as air passes through the hollow in the middle.
  • This portion rises and falls during swallowing of food particles.
  • The epiglottis is one of the cartilage pieces of the larynx.
    • Serves as the cover of the larynx during swallowing.
  • The larynx contains special structures known as vocal folds and these allow the body to produce the sounds of speech and singing.


  • It is a wide hollow space the nasal chambers open up into.
  • It acts as a common path for both air and food.
  • It functions by preventing the entry of food particles into the windpipe.
  • The pharynx, also known as the throat, is a muscular funnel.
  • Extends from the posterior end of the nasal cavity to the superior end of the oesophagus and larynx.


  • It is also known as the windpipe, 5-inch long tube made of C-shaped hyaline cartilage rings.
  • The trachea connects the larynx to the bronchi.
  • It also allows air to pass through the neck and into the thorax.
  • The trachea or the windpipe rises below the larynx and moves down to the neck.
  • Providing a clear airway for air to enter and exit the lungs is the main function of the trachea.


  • The trachea splits into two tubes termed as bronchi.
  • Division of bronchi:
    • Secondary
    • Tertiary
  • The bronchioles are further divided into small air sacs called the alveoli.
  • The secondary bronchi carry air into the lobes of the lungs.
  • The tertiary bronchi split into many smaller bronchioles that spread throughout the lungs.


  • A pair of large, spongy organs found in the thorax.
    • Lateral to the heart and superior to the diaphragm.
  • The left and right lungs are slightly different in size and shape.
    • Due to the heart pointing to the left side of the body.
  • The left lung is made up of two lobes while the right lung has three lobes.
  • The lungs act as the chief centres of the respiration in humans and other vertebrates.
  • The interior of the lungs is made up of spongy tissues.

Respiration in Humans

The process of taking in oxygen and giving out carbon dioxide is known as respiration.

External Respiration

This involves the inhalation and exhalation of gases.

Internal Respiration

It involves the exchange of gases between blood and body cells.

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