Respiratory System
MUHAMMAD HAMMAD
AP BIOLOGY
BLOCK 6
Functions
 The main function of the respiratory system is gas
exchange. When one inhales, oxygen enters the
blood by means of alveoli and capillaries. It is then
carried to different tissues by blood. Carbon dioxide
is collected by the blood and carried to the lungs.
CO2 diffuses from the capillaries and is exhaled as a
waste product.
Importance
 The human needs oxygen to sustain itself.
 Anoxia- complete lack of oxygen
 Hypoxia- decrease in oxygen
***After 4 to 6 minutes with anoxia or hypoxia, brain
cells are completely destroyed leading to death.
Organs of the Respiratory System
 Lungs- supply the body with oxygen and remove carbon dioxide.
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They are present in the pleural cavities.
Nose- organ through which air is inhaled and exhaled
Pharynx- allows the passage of air to the lungs. Located behind the
nasal and oral cavities.
Epiglottis- prevents food or water from entering the trachea. Flap
like structure.
Larynx- controls the flow of air
Trachea- facilitates the flow of air to the bronchi. Also known as the
windpipe.
Bronchi- passage which allows the flow of air to the lungs.
Alveoli-interface for the exchange of oxygen and carbon dioxide
between lungs and capillaries. Sac shaped bodies
Diaphragm-creates a partition between the thoracic and abdominal
cavity
Quick Facts
 The rate at which human beings breathe is 12-18
breaths per minute. There are 1440 minutes in 24
hours, therefore, the average number of breaths
drawn in by a human (at a rate of 12 breaths per
minute) in a day's time is 17,280.
 There are over 600 million alveoli in the lungs of an
adult human being.
 The right and left lungs of the human respiratory
system do not have the same size. In fact, the left
lung is a bit smaller than the right one.