Which term describes the circulation of blood to tissues?

• A. Perfusion
• B. Oxygenation
• C. Ventilation
• D. Respiration

Answer: (A)

Perfusion is the circulation of blood through the body's tissue beds, delivering oxygen and nutrients and removing waste products. It reflects how well blood reaches the microvasculature of tissues to meet their metabolic needs. Oxygenation, by contrast, refers to how much oxygen is bound to hemoglobin and carried in the blood, a process that occurs mainly in the lungs and is not the same as delivering that blood to tissues. Ventilation is about moving air into and out of the lungs to enable gas exchange, which is from the lungs to the blood, not the distribution of blood to tissues. Respiration can refer to cellular energy production that uses oxygen or, in some contexts, the overall gas-exchange process, but again it is distinct from the flow of blood through tissue beds. So the term that describes the circulation of blood to tissues is perfusion, and its adequacy depends on factors like cardiac output and vascular supply to meet the tissues’ metabolic demands.