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.
1 gas exchange is the ventilation of gases to and from the body cells of an animal so cellular respiration can take place. 2  gas exchange surfaces provide an area for gases to be exchange between the medium (air or water) and body cells, usually enclosing a moving blood supply. gas exchange is the ventilation of gases to and from the body cells of an animal so cellular respiration can take place. 2  gas exchange surfaces provide an area for gases to be exchange between the medium (air or water) and body cells, usually enclosing a moving blood supply.