What is the term for the opposition to blood flow through blood vessels?

The term that describes the opposition to blood flow through blood vessels is peripheral vascular resistance. This refers to the resistance encountered by blood as it travels through the peripheral circulation, primarily determined by the diameter of the blood vessels and the overall vascular tone. The smaller the vessel diameter, the higher the resistance and, consequently, the more pressure the heart must generate to maintain adequate blood flow.

Understanding peripheral vascular resistance is crucial because it plays a significant role in regulating blood pressure and establishing proper blood circulation throughout the body. Changes in this resistance can impact overall cardiovascular health, making it an important concept in both physiology and medicine. The other terms listed pertain to different aspects of cardiovascular function: blood pressure is the force exerted by circulating blood on the walls of blood vessels, cardiac output is the volume of blood pumped by the heart per minute, and blood viscosity refers to the thickness and stickiness of blood, which can affect flow but is not a direct measure of resistance itself.