Oxygen is the main base of the life of all the living organisms whether it is human being, animal or small creatures. We take in (inhale) oxygen while breathing that helps us in being alive. Oxygen, after reaching in lungs, is mixed with blood and then is circulated (forwarded) in the entire body along with blood. In this way, when we breathe out (exhale), carbon dioxide comes out from the body. Breathing in (inhaling) and breathing out (exhaling) is together called respiration.   

Respiratory system-

  1. Respiration is based on respiratory tract and two lungs. The respiratory tract starts from nose and mouth, from where air enters, and goes down by crossing the rear section of the throat which the path of food and air. A cord (flat) is located on the upper part of larynx that is closed while swallowing food or liquid materials for preventing air to enter. Air passes through the pharynx, the rear section of the throat, and larynx and reached in trachea which is divided in to two bronchi. The bronchi is further divided into small tubes in each lungs resulting a network of tubes are formed. These small tubes are reached in the air sacs of the lungs. 

Process of respiration-

  • There are three phases of respiration- inspiration (inhaling), expiration (exhaling) and pause (holding breathe).
  • Patal, along with muscles of the ribs, helps in inspiration and expiration.
  • When we breathe in (inhale) air enters in the flexible and spongy lungs inside the body resulting the patal moves downwards and the chest is expanded. When we breathe out (exhale), the lungs are contracted. The process of inhaling is active and the process of exhaling is inactive.
  • An adult breathes approx. 15-20 times in a minute.
  • Whole the respiratory system is controlled by respiratory center located in the brain.

Structure of air- air has 70% nitrogen and 21% oxygen. The air we breathe out has about 16% oxygen and remaining is carbon dioxide.

Function of lungs- The lungs help in the filtration of blood. Oxygen present in air, after reaching in lungs, is pumped in to blood and carbon dioxide is also removed out from the body by exhaling.