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•  Ventilation maintains concentration gradients of oxygen and carbon dioxide between air in alveoli and blood

    flowing in adjacent capillaries

Physiological respiration involves the transport of oxygen to cells within the tissues, where energy production occurs

  • It is comprised of three distinct processes and is not to be confused with cellular respiration (a single component of the activity)

The processes involved in physiological respiration are:

  • Ventilation:  The exchange of air between the atmosphere and the lungs – achieved by the physical act of breathing
  • Gas Exchange:  The exchange of oxygen and carbon dioxide between the alveoli and bloodstream (via passive diffusion)
  • Cell Respiration:  The release of energy (ATP) from organic molecules – it is enhanced by the presence of oxygen (aerobic)

physiological respiration

Purpose of Ventilation

Because gas exchange is a passive process, a ventilation system is needed to maintain a concentration gradient in alveoli

  • Oxygen is consumed by cells during cellular respiration and carbon dioxide is produced as a waste product
  • This means O2 is constantly being removed from the alveoli into the bloodstream (and CO2 is continually being released)

The lungs function as a ventilation system by continually cycling fresh air into the alveoli from the atmosphere

  • This means O2 levels stay high in alveoli (and diffuse into the blood) and CO2 levels stay low (and diffuse from the blood)
  • The lungs are also structured to have a very large surface area, so as to increase the overall rate of gas exchange

Ventilation System

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