Respiration is the biochemical process in which the cells of an organism obtain energy by combining oxygen and glucose, resulting in the release of carbon dioxide, water, and ATP.

Respiration is the process of chemical reactions that occur inside cells in the body. Respiration allows cells to release energy.


  • Surfactant is a mixture of lipids and proteins which is secreted into the alveolar space by epithelial type II cells.
  • The main function of surfactant is to lower the surface tension at the air/liquid interface within the alveoli of the lung.
  • Surfactant contributes to the elastic properties of pulmonary tissue, preventing the alveoli from collapsing.
  • Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents, and dispersants.


  • The functional unit of lung is called as alveoli.
  • Alveoli are tiny sacs within our lungs that allow oxygen and carbon dioxide to move between the lungs and bloodstream.
  • The primary function of the respiratory system is to exchange oxygen and carbon dioxide. Inhaled oxygen enters the lungs and reaches the alveoli.
  • Oxygen passes quickly through the air-blood barrier into the blood in the capillaries.
  • Carbon dioxide passes from the blood into the alveoli and is then exhaled.


Vital capacity (VC) – Vital capacity (VC) :

  • Is the maximum amount of air a person can expel from the lungs after a maximum inhalation.
  • It is equal to the sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume.

Tidal volume (TV): –

  • Normal volume of air displaced between normal inhalation and exhalation when extra effort is not applied.
  • Tidal volume (symbol VT or TV) is the lung volume representing the normal volume of air displaced between normal inhalation and exhalation when extra effort is not applied.
  • Tidal volume is approximately 500 mL per inspiration or 7 mL/kg of body mass.

Inspiratory reserve volume (IRV) :–

The maximal amount of additional air that can be drawn into the lungs by determined effort after normal inspiration (usually up to 2500 ml).

Expiratory reserve volume (ERV) :–

The additional amount of air that can be expired from the lungs by determined effort after normal expiration (up to 1000 ml).

Functional residual capacity (FRC): 

The amount of air remaining at the end of normal quiet respiration, the summation of ERV and RV.

Lung volumes and lung capacities: 

  • Refer to the volume of air associated with different phases of the respiratory cycle. What
  • The average total lung capacity of an adult human male is about 6 litres of air.
  • Tidal breathing is normal, The tidal volume is the volume of air that is inhaled or exhaled in only a single such breath.
  • The average human respiratory rate is 30-60 breaths per minute at birth,decreasing to 12-20 breaths per minute in adults.

Physiological dead space:

  •  Dead space is the volume of a breath that does not participate in gas exchange.
  • It is ventilation without perfusion. they  remains in the conducting airways, or reaches alveoli that are not perfused or poorly perfused.
  • Physiologic or total dead space is the sum of anatomic dead space and alveolar dead space.

Anatomic dead space:

Anatomic dead space specifically refers to the volume of air located in the segments of the respiratory tract that are responsible for conducting air to the alveoli and respiratory bronchioles but do not take part in the process of gas exchange itself.

Residual volume (RV):

  • The volume of air still remaining in the lungs after the most forcible expiration possible and amounting usually from 1000 to 1500 ml.
  • It can be measured only by special equipment.


By drcathyhappy2serve

Hi. My name’s Cathy.And I’m glad to see you here. Here’s what you really need to know about me:I am a big fan of Body and Health. I love to learn about it. I love to grow in it. And I love to help others develop as Healthy Human.. And… I’m not a fan of technology. So a Web-Site might seem like an odd fit for me. So why am I here online? Because you are. For many years I’ve been able to help People through Consultation at Clinic, Conference at public, as a trainer Fitness Centre , and as articles in books. But in this 21st Century, more and more people are searching for resources on the Internet. So it’s time for me to bring my material to the world of computers. I hope to provide you with Physical Fitness teaching that is both timeless and timely. I’ll let you in on my book writing process. I’ll tell you what I’m reading. And occasionally, I’ll tell you what I think about what’s currently happening in the world of Physical Fitness and Health Conciousness — around the world. My hope is that what you find here will add value to your life and give you the tools to achieve your goals as a Healthy Human Being.

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