The respiratory system (or ventilatory system) is the biological system of an organism that introduces respiratory gases to the interior and performs gas exchange. In humans and other mammals, the anatomical features of the respiratory system include airways, lungs, and the respiratory muscles. Molecules of oxygen and carbon dioxide are passively exchanged, by diffusion, between the gaseous external environment and the blood. This exchange process occurs in the alveolar region of the lungs. Other animals, such as insects, have respiratory systems with very simple anatomical features, and in amphibians even the skin plays a vital role in gas exchange. Plants also have respiratory systems but the directionality of gas exchange can be opposite to that in animals. The respiratory system in plants also includes anatomical features such as holes on the undersides of leaves known as stomata.Scientists are researching our respiratory system, and here are links to some of their research.
The ingredient 2,3-pentanedione (PD), used to impart the flavor and aroma of butter in microwave popcorn, is a respiratory hazard that can also alter gene expression in the brain of rats. Manufacturers started using PD when another butter flavoring, diacetyl, was found to cause bronchiolitis obliterans, a life-threatening and nonreversible lung disease in workers who inhaled the substance. New research on PD with implications for "popcorn workers' lung" is published in The American Journal of Pathology and indicates that acute PD exposure has respiratory toxicity which is comparable to diacetyl in laboratory animals.