Difference between Inhalation and Exhalation | Class 12 Biology Notes

Biology | Zoology
HSEB Notes on Respiratory Organs and Mechanisms of Breathing
Lesson :  Respiration
Class : 12

Difference between inhalation and exhalation

Please compare the point of Inhalation with the point of Exhalation 

Inhalation 

1. Taking in of atmospheric air 

2. contraction of external intercostal muscle or inspiratory muscle and relaxation of internal intercostals muscle.

3. rib cage moves forward and outward 

4. diaphragm contracts and becomes 

flattened. shaped.

5. increase in the volume of thoracic cavity. 

6. decease in air pressure(below atmos- 

pheric pressure.

7. rushing in of air through nostril into 

alveolar sacs causing inflation of lung.

Exhalation

1. giving out of air from lungs.

2. relaxation of external intercostals muscle and contraction of intercostal  muscle.

3. rib cage moves downward and inward.

4. diaphragm relaxes and become dome 

5. decrease in volume of thoracic cavity.

6. increase in the air pressure.

7. expulsion of air from lungs into atmosphere causing deflation of lungs.

One breath includes one inspiration or inhalation and one expiration of exhalation. The respiratory rate is the no. of breaths taken per minute. At rest, for a normal person, it is equal to 12 to 14 breaths per minute. The pulmonary air volume during breathing is measured by an apparatus called Spirometer. 

• Tidal volume(TV) - volume of air that is breathed in or out during effortless normal breathing. It is about 500 ml.
• Inspiratory reserve volume(IRV) - it is an extra volume of air over and above the tidal volume that can be taken in during a deep breath. It is about 1500 to 2500 ml.
• Expiratory reserve volume(ERV) - after a normal expiration one can still expel a large volume of air. It is known as ERV. It is about 1500 ml.
• Vital capacity(VC) - it is total volume of air expired after a maximum inspiration. It is about 3.5 to 4.5 L for normal adult and about 6 L for athlete. 
• Total lung capacity(TLC) - it refers to amount of air present in the lung after maximum inhalation. It is equivalent to 5 to 5.5 L 
• Residual volume)RV) - it is the amount of air left in the lungs even after maximum expiratory effort. It can never be forced out of lungs. It is about 1500 ml.
• Dead space - it is amount of air that is present in the respiratory tubes where gases exchange does not occur. With each expiration it is expelled out without undergoing any change in O2 and CO2 concentration. It is equivalent to about 150 ml. Out of tidal volume of 500 ml, 150 ml remains in the respiratory tubes as dead space and the only the rest of 350 ml is present in alveolar sacs in the lungs for exchange of gases. 
• Respiratory Quotient - it is the ratio of volume of CO2 produced and volume of O2 used during the respiration. It is RQ in short. 

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