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. the exchange of oxygen and carbon dioxide between the atmosphere and the body cells, including ventilation (inhalation and exhalation); diffusion of oxygen from alveoli to blood and of carbon dioxide from blood to alveoli; and transport of oxygen to and carbon dioxide from body cells. 2. ventilation (1).