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 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.he surface area for gas exchange is correlated with metabolic rate. Endotherms, such as birds and mammals, have a high metabolic rate and a correspondingly high respiratory surface area. Birds have one-way flow through their lungs, enabled by a complex system of air-storing sacs.