Buna is a census-designated place in Jasper County, Texas, United States. The population was 2,142 at the 2010 census.
Gas Exchange. 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.
Gas exchange is part of breathing. Breathing is a vital function of life; it helps your body work properly. Other organs and tissues also help make breathing possible. (For more information, go to The Respiratory System section of this article.).