Carbon dioxide is essential in the role of internal respiration.

Internal respiration refers to the process by which oxygen'is transported to body tissues and carbon dioxide is carried away from them.

Internal respiration is defined as the process that provides oxygen to cells and carries the product of metabolism, (carbon dioxide), to the lungs.

RESPIRATORY SYSTEM 1. Induces deep breathing. 2. Decreases external and internal respiration.

Artificial respiration is the act of assisting or stimulating respiration, a metabolic process referring to the overall exchange of gases in the body by pulmonary ventilation, external respiration, and internal respiration.

Assistance takes many forms, but generally entails providing air for a person who is not breathing or is not making sufficient respiratory effort on his/her own (although it must be used on a patient with a beating heart or as part of cardiopulmonary resuscitation to achieve the internal respiration).

Organisms with internal gas exchange surfaces need mechanisms for conveying gases between the environment and these surfaces.

Internal gas exchange is more pronounced in slices from the leaves of maize (a C-4 plant) having the complex Kranz tissue differentiation of mesophyll and bundle sheath, than in the leaves of barley (a C-3 plant).