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 in the human body occur in lungs. it is described as follows:- When we inhale atmospheric air, through the nose it go to the trachea and then via bronchus and bronchioles it ultimately go to the alveolus where exchange of different gas takes place.