Introduction to the Human Respiratory System
Simple diagram of the lower respiratory tract. (Click here for a more detailed diagram.)
Above: Lower respiratory tract (more detail)
This page gives a very simple overview of the structure and functions of the human respiratory system.
About Respiration
Respiration consists of:
- Breathing (inspiration and expiration),
- 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 : |
NARES |
NASO PHARYNX |
EPIGLOTTIS |
LARYNX |
 |
Lower Respiratory Tract : |
TRACHEA |
(BIFICATES INTO 2 BRONCHI) |
BRONCHIOLES |
UPPER |
ALVEOLAR DUCTS |
ALVEOLAR SACS |
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 notes about other aspects of the respiratory system incl. pulmonary circulation.
