Final answer:
The nonrigid stretchability of vessels is known as compliance, which is crucial for allowing blood vessels to expand and accommodate changes in volume and pressure without increasing resistance or causing higher pressure.
Step-by-step explanation:
The nonrigid stretchability of vessels is termed compliance. When thinking about compliance in the context of blood vessels, consider the ability of the vessel walls to expand and accommodate changes in blood volume and pressure. The concept is akin to how a balloon can stretch when filled with air; the more compliant the balloon, the more air it can hold without popping.
In the human body, veins are known for being highly compliant, as they can hold more blood and expand when necessary without significantly increasing resistance or pressure. Arteries also exhibit compliance, although to a lesser extent than veins. This vascular compliance is crucial for maintaining steady blood flow and pressure throughout the circulatory system. However, when diseases cause the arterial walls to stiffen and lose their compliance, the result can be a higher risk of turbulence, increased pressure, and the potential for reduced blood flow, all of which add workload on the heart.
In conclusion, the correct option for the nonrigid stretch-ability of vessels, often measured to evaluate the health of the arterial system, is A. Compliance