Final answer:
The factors that determine pulmonary vascular resistance are viscosity, vessel length, and vessel radius.
Step-by-step explanation:
The three factors that determine pulmonary vascular resistance are viscosity, vessel length, and vessel radius.
Viscosity refers to the thickness or stickiness of the blood. Blood with higher viscosity will flow more slowly, leading to increased resistance.
Vessel length refers to the length of the blood vessels. Longer vessels will have higher resistance because the blood has to travel a greater distance.
Vessel radius or diameter is the most important factor determining resistance. The narrower the blood vessel, the higher the resistance. Even small changes in vessel radius can have a significant impact on resistance and blood flow.