Lung Volumes

Lung Volumes and Capacities

Lung is the primary respiratory organ of animals. However, the structure and capacities are different amongst various species. 

For example, the structure of a dog’s lungs is smaller than humans. Also, the lungs of a sparrow are different as they can fly.  

Lung volumes and capacities are two significant terms in the respiratory system. It is determined based on Human breath, which is a full respiratory circle of one inspiration and expiration. 

Lung Volume

Lung volume is also called respiratory volume. An instrument called Spirometer helps in measuring Respiratory volumes. 

The lung volume definition tells that it calculates how much air moves in and out of the lungs. It also helps in examining the physical condition of the lungs and overall pulmonary system. 

The main components of lung volume are following.

  • Tidal Volume (TV) - It is the amount of air moves in and out of the lungs in normal respiration. The amount is approximately 500ml. Adult human breaths 12 to 15 times per minute. Hence, a person intakes 6000-8000 ml air in a minute.

  • Inspiratory Reserve Volume (IRV) – This term means the additional volume which human inspire while taking a long deep breath. It ranges from 2500-3000 ml.

  • Expiratory Reserve Volume (ERV) – That extra volume that an adult expires at the time of a forcible expiration. The approximate range is 1000-1100 ml. 

  • Residual Volume (RV) – Even after a forcible expiration, a specific volume of air remains in the lungs. It usually varies between 1100-1200 ml. 

However, a sum of all these volumes helps in deriving lung capacities which is useful in finding out pulmonary disorder. 

Lung Capacity

Human lung capacity is calculated by adding two or more lung volumes. 

  • Inspiratory Capacity(IC) - It shows the total volume of air a person inspires during a normal respiration. It is the addition of Inspiratory Reserve Volume and Tidal Volume. Thus, IC= IRV+TV

  • Expiratory Capacity (EC) - This suggests a total amount of air an adult exhales during a normal breathing process. A summation of expiratory Reserve Volume and Tidal Volume, its formula is EC= ERV+TV. 

  • Functional Residual Capacity (FRC) - As the name suggests, it indicates the quantity of air that stay in the lungs after a normal breath. It is FRC= RV+ ERV. 

  • Vital Capacity (VC) - It denotes the highest air volume that a person can inspire after breathing out forcibly. Similarly, the amount of air person can expire after breathing in forcibly. VC= IVR+TV+EVR. 

  • Total Lung Capacity (TLC) - It shows the maximum air quantity that lungs can allow after a forcible inspiration. Total lung capacity formula is TLC= TV+IRV+ERV+RV. 

Besides, total lung capacity in ml is near about 6000 ml. 

Now it’s your turn to write a note on the functions of lungs in exchanging gases through alveoli. 

Lung Volumes and Capacities Normal Value 

The following table will show lung volumes and capacities values. 

Respiratory Volumes and Capacity Measurement

Primarily, the following methods are most popular in calculating these two factors. 

  • Nitrogen washout- It helps in calculating anatomical/serial dead space. 

  • Helium dilution- This Measures total lung capacity. 

MCQ

  1. The amount of air a person cannot breaths out and is about 1200ml. It is-

  1. Residual volume

  2. Vital capacity

  3. Expiratory reserve volume

Ans. a)

  1. What is the function of alveoli?

  1. Removing air

  2. Gaseous exchanges and diffusion

  3. Allowing air to enter alveoli

Ans. b)

Lung Volume vs Lung Capacity

There is a stark difference between these two terms. The first one shows the quantity of air for a single function. For example, breathing in or out. The last one tells the maximum amount of air lungs can hold. For instance, it is the sum of two or more lung volumes. 

For a more detailed account of respiratory mechanisms, go through our additional study materials today! Don’t forget to take a look at our rest of the notes for a detailed insight on various chapters of Biology. You can also access all of our course materials from Vedantu’s app as well.

FAQ (Frequently Asked Questions)

1. What is vital capacity?

Vital capacity is the maximum amount of air that expels from the lungs after a long inhalation. 

2. How much air can a person hold in the lungs?

On average, an adult male can hold 6 litres of air in the lungs. It is called Total Lung Capacity. 

How to calculate lung capacity?

The sum of inspiratory reserve volume, tidal volume, expiratory reserve volume and residual volume denotes lung capacity. The result varies with age and body weight.