Oxygen
Gas exchange is the process by which oxygen and carbon dioxide (the respiratory gases) move in opposite directions across an organism's respiratory membranes, between the air or water of the external environment and the body fluids of the internal environment. 1. the exchange of oxygen and carbon dioxide between the atmosphere and the body cells, including inspiration and expiration, diffusion of oxygen from the pulmonary alveoli to the blood and of carbon dioxide from the blood to the alveoli, and the transport of oxygen to and carbon dioxide from the body cells. 1. the exchange of oxygen and carbon dioxide between the atmosphere and the body cells, including inhalation and exhalation, diffusion of oxygen from the pulmonary alveoli to the blood and of carbon dioxide from the blood to the alveoli, followed by the transport of oxygen to and carbon dioxide from the body cells. Diffusion allows substances to pass into or out of cells across the cell membrane-but they must be dissolved and there must be a concentration gradient present between the solutions on either side of the cell membrane. Diffusion is a very important exchange process which is widely used in living organisms. The blood is the transport system by which oxygen and nutrients reach the body's cells, and waste materials are carried away. In addition, blood carries substances called hormones, which control body processes, and antibodies to fight invading germs. Capillary to Tissue Fluid Exchange. Capillaries are where fluids, gasses, nutrients, and wastes are exchanged between the blood and body tissues by diffusion. Capillary walls contain small pores that allow certain substances to pass into and out of the blood vessel. Exchange between cells and capillaries. All cells use up oxygen to release energy. This oxygen comes from the red blood cells in the nearby capillaries by diffusion. The carbon dioxide which is produced by respiration in the cells diffuses into the blood plasma. The blood plasma also contains dissolved food which is being transportedfrom the digestive system to the cells. Most of the gas exchange in the body takes place in the capillaries. Oxygen diffuses from high concentration in the blood to lower concentrations in body cells. Carbon dioxide diffuses from high concentration in the body cells to lower concentrations in the blood.
http://www.biologyreference.com/Fo-Gr/Gas-Exchange.html http://medical-dictionary.thefreedictionary.com/internal+respiration http://medical-dictionary.thefreedictionary.com/internal+respiration http://www.bbc.co.uk/schools/gcsebitesize/science/triple_aqa/movement_of_molecules/dissolved_substances/revision/1/ http://www.ambulancetechnicianstudy.co.uk/circsystem.html http://biology.about.com/od/anatomy/ss/capillary.htm http://www.bbc.co.uk/bitesize/standard/biology/the_body_in_action/the_need_for_energy/revision/9/
substances are exchanged between the blood and body cells in the