Which process occurs as de-oxygenated blood travels to the lungs?

The process that occurs as de-oxygenated blood travels to the lungs is known as external respiration. This term refers specifically to the exchange of gases between the air in the lungs and the blood within the pulmonary capillaries. When de-oxygenated blood reaches the lungs, carbon dioxide is expelled from the blood, and oxygen from the air is absorbed into the blood. This vital exchange is essential for replenishing oxygen levels in the bloodstream and removing waste gases from the body.

In contrast, internal respiration takes place at the cellular level throughout the body where oxygen is delivered to cells and carbon dioxide is collected as a waste product. Blood circulation refers broadly to the movement of blood throughout the body, encompassing both oxygenated and de-oxygenated blood, rather than focusing on the specific gas exchange process. Pulmonary ventilation pertains to the mechanical process of breathing, which involves the inhalation and exhalation of air, but is not the same as the exchange of gases happening in the lungs. External respiration uniquely captures the essence of gas exchange during the time de-oxygenated blood is in the lungs, making it the correct answer in this context.