[Biology Class Notes] on Lung Volumes Pdf for EXAM

Lungs are a pair of organs located within the chest, which help in breathing. In simple words, lungs remove carbon dioxide and bring oxygen to the blood. Lungs are the primary respiratory organs of animals. In spite of the functionality, the structure and capacities are different amongst various species. 

Different animals have different lung capacities based on the size of the body and the activities they perform. For example, the lung capacity of an elephant is greater than that of a human due to its large body size. Also, the lung capacity of animals like cheetahs and gazelles is very high because they require a large amount of oxygen for their muscles in order to run at very high speed. 

A human lung has a capacity to hold a maximum of six litres of air. The device that is used to measure the volume of air involved is called a spirometer. It is a medical apparatus that is used to determine the amount of air you are able to breathe in and out and the time you take to completely exhale the air after you take a deep breath.

Lung volume and lung capacity are used to measure air present in the lungs. Lung volume measures the amount of air present for a living being to inhale or exhale. On the other hand, lung capacity is the volume of air in the lungs upon the maximum effort of inspiration.

Lung Volumes and Capacities

The 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 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 the rest of our notes for a detailed insight on various chapters of Biology.

Lung Volumes and Lung Capacities

Tidal Volume

The tidal volume is the total amount of air inhaled or exhaled during normal breathing. On an average 500 ml of air is utilised during normal respiration in a healthy man.

Inspiratory Reserve Volume

An inspiratory reserve volume is a supplementary volume, ranging between 2500 to 3100 ml of air which could be inhaled effectively after the inspiration of a standard Tidal Volume.

Expiratory Reserve Volume

The extra volume of air that can be exhaled from the lungs with effort following a normal tidal volume expiration. An expiratory reserve volume is about 1200 ml that could be forcibly exhaled out after the expiration of a standard tidal volume.

Residual Volume/Reserve Volume

The residual volume is the total volume of air that is around 1100 ml to 1200 ml, residing in the lungs after the reserve volume is exhaled or breathed out.

Lung Capacity

Total Lung Capacity

The total lung capacity is the total volume of air in the lungs after a forced inspiration. The lung capacity of a healthy man is around 6000 ml.

TLC = TV + ERV + IRV + RV

Vital Capacity

The vital capacity is the total volume of air that can be breathed out after inhalation limit or maximum air that a person can breathe in after forced expiration. It is an essential measure of a person’s respiratory health. A decreased vital capacity indicates restrictive lung disease where the lungs cannot expand completely. In the general case of normal vital capacity, the improper functioning of lungs indicates obstructive lung disease, where the lungs are blocked in the airways.

VC = TV + ERV + IRV

Inspiratory Capacity

The amount of extra air inhaled above tidal volume during a forceful inspiration. The average inspiratory reserve volume is about 3000 mL in males and 2100 mL in females.

IC = TV + IRV

Functional Residual Capacity

Functional Residual Capacity is the volume remaining in the lungs after a normal exhalation. In a healthy individual, this is about 3L.

FRC = ERV + RV

Respiratory Volumes and Capacity Measurement

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

Relevant MCQs

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

1. Residual volume

2. Vital capacity

3. Expiratory reserve volume

Ans. a)

2. What is the function of alveoli?

1. Removing air

2. Gaseous exchanges and diffusion

3. Allowing air to enter alveoli

Ans. b)

3. A person normally passively inhales and exhales 500 mL of air. This is the _______.

1. Tidal volume

2. Expiratory capacity

3. Residual Volume

Ans. a)