Respiration occurs in all the body cells of an organism. If you look at the equation for respiration for respiration ,you will notice that oxygen is needed and carbon dioxide is produced. CO2 is a waste gas and it must be remove d from the organism. Therefore ,organisms have to take oxygen into their bodies from their surroundings and get rid of carbon dioxide. This exchange of oxygen and carbon dioxide is called gaseous exchange.
¡@
Breathing in humans
The diaphragm muscles and the intercostal muscles between the ribs are the primary respiratory muscles. The abdominal muscles play a minor role.
Inspiration (inhalation): When the diaphragm is contracted it flattens, and when the external intercostal muscles contract the ribs are raised upwards and forwards, and the chest cavity is enlarged. The pressure within the thoracic cavity decreases. Since the spaces within the lungs are open to the atmosphere the higher atmospheric pressure forces air into the lungs until the pressure is equalized. Because the lungs contain elastic connective tissue, they become inflated with airExpiration (exhalation): Relaxation of the diaphragm allows it to return to its convex (upward) domed position. The external intercostal muscles relax and the internal intercostal muscles contract, moving the ribs inwards and downwards, thus decreasing the volume of the thoracic cavity. The air pressure in this cavity is increased and air is forced out of the lungs.
¡@
¡@
Index about Animal Kingdom birds mammals Amphibians reptiles fish
Plant Kingdom monocotyledons dicotyledons Gymnosperms Ferns Algae Fungi
gaseous exchange breathing system Respiration Experiment ( ©I§l§@¥Î¹êÅç ) Smoking and your health
Copyright (c) 2001 (http://www.oocities.org/hkbiology). All Rights Reserved.