Introduction to the Human Respiratory System

Simple diagram of the lower respiratory tract. (Click here for a more detailed diagram.)

This page gives a very simple overview of the structure and functions of the human respiratory system.

About Respiration

Respiration consists of:

  1. Breathing (inspiration and expiration),
  2. Gaseous Exchange (exchange of gases between the lungs / blood and blood / tissues and vice-versa).

It is controlled by the autonomic nervous system (ANS),
specifically the medulla oblongata.


Basic Structure of the Respiratory System

Below is a very simple diagram in which the respiratory system is represented by a flow-chart indicating the route by which oxygen flows into the body via the airways then travels to the surfaces at which gaseous exchange with tissues occurs:

Upper Respiratory Tract :






Lower Respiratory Tract :
(Click to view this section as a diagram instead)







Although the above is a good starting point from which to memorise the structures one might need to identify in an exam, further detail will be needed when asked to "describe by means of a diagram", or similar. All but the simplest texts illustrate the upper-respiratory tract and the lower-respiratory tract separately.


Facts about the Human Respiratory System

  • There are two lungs in the body, the total surface area of both of these combined being equivalent to that of about 2 tennis courts (per normal adult).
  • All of the blood in the body circulates through the lungs each time it passes around the body.
  • If laid end-to-end the capilliaries of the lungs would stretch for approx. 44 miles (70 km).

See also information about other aspects of the respiratory system incl. notes about pulmonary circulation.

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