The Respiratory System

The Respiratory System

Author: Nicholas Holmes


  • to transfer a basic understanding of the human Respiratory System and gaseous exchange

a comprehensive introduction to the respiratory system and gaseous exchange

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What is the Respiratory System?

The respiratory system (or ventilatory system) is the biological system that introduces respiratory gases to the interior and performs gaseous exchange.

  • In humans and other mammals, the anatomical features of the respiratory system include airwayslungs, and the respiratory muscles
  • Molecules of oxygen and carbon dioxide are passively exchanged, by diffusion, between the gaseous external environment and the blood. This exchange process occurs in the alveolar region of the lungs.

Gaseous Exchange

Air first enters the body through the mouth or nose, quickly moves to the pharynx (throat), passes through the larynx (voice box), enters the trachea, which branches into a left and right bronchus within the lungs and further divides into smaller and smaller branches called bronchioles. The smallest bronchioles end in tiny air sacs, called alveoli, which inflate during inhalation, and deflate during exhalation.

Gas exchange is the delivery of oxygen from the lungs to the bloodstream, and the elimination of carbon dioxide from the bloodstream to the lungs. It occurs in the lungs between the alveoli and a network of tiny blood vessels called capillaries, which are located in the walls of the alveoli.

The walls of the alveoli actually share a membrane with the capillaries in which oxygen and carbon dioxide move freely between the respiratory system and the bloodstream. Oxygen molecules attach to red blood cells, which travel back to the heart. At the same time, the carbon dioxide molecules in the alveoli are blown out of the body with the next exhalation.