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The importance of oxygen for human body can neither be under nor over estimated and this “essential for life” function of oxygen delivery to body cells is performed by the RESPIRATORY SYSTEM through the process of BREATHING. Not only this, breathing helps body get rid of the waste product of cellular respiration, i.e. carbon dioxide. This exchange of oxygen and carbon dioxide occurs at the level of lungs in the respiratory system. Even though breathing is an unconscious affair, something we are not even aware of doing all the time, our body has many ways of regulating and controlling this function through a complex mechanism of interdependent pathways.



Respiratory system is an integrated system of organs involved in the intake and exchange of oxygen and carbon dioxide between an organism and the environment.


The respiratory system is made up of:

  • Nose
  • Pharynx
  • Larynx
  • Trachea
  • Bronchi
  • Lungs

The primary function of the respiratory system is to supply the blood with oxygen in order for the blood to deliver oxygen to all parts of the body and to remove carbon dioxide.

This process starts with the oxygen rich air entering the nose or mouth which then moves down the trachea, bronchi and finally reaches the lungs.

Each of the organs of respiratory system thus plays an important part in the process of respiration but the lungs are the site where actual exchange of gases takes place.


The lungs are a pair of cone-shaped, soft, spongy, pinkish organs. They are located in the anterior chest or the thorax.

Functions of Lungs

Two types of functions are performed by lungs:

  • Respiratory functions
  • Non-respiratory functions

Respitory Functions

The primary function of lungs is “gas exchange” i.e. to exchange oxygen from air with carbon dioxide from blood. The process in which this happens is called “external respiration” or breathing.

The average adult’s lungs contain about 600 million spongy, air-filled sacs called alveoli that are surrounded by capillaries. The inhaled oxygen passes into the alveoli and then diffuses through the capillaries into the arterial blood. Meanwhile, the waste-rich blood from the veins releases its carbon dioxide into the alveoli. The carbon dioxide then follows the same path out of the lungs (as oxygen coming inside the lungs) when we exhale.

Non-Respitory Functions

These are categorized as:

  • Mechanical
  • Biochemical
  • Physiological

The lungs defend the body from potentially dangerous airborne pollutants and toxic chemicals produced by our own body. They are the first line of defense against airborne bacterial and viral agents, other infectious agents and irritants. The lungs control the flow of water, ions and proteins across its cellular structures. The lungs manufacture certain essential hormones and other chemicals for very specific functions in the body. They remove volatile particles and substances generated within the body. With the liver, they act as the metabolic product “removals services” of the body.


Main goals of the respiratory control system