Kaplan Nursing Entrance Practice Exam

How do veins differ from arteries in terms of structure?

1. Veins are thicker and have no valves

2. Veins are thinner and have valves to prevent backflow

3. Veins conduct blood at high pressure

4. Veins contain more muscle and elastic fibers

The correct answer is: Veins are thinner and have valves to prevent backflow

Veins have a distinct structural design that facilitates their primary function of returning blood to the heart. Unlike arteries, which are designed to handle higher pressures and have thicker walls due to the presence of more muscle and elastic fibers, veins are characterized by their thinner walls. This allows for greater capacity to hold blood, which is crucial since veins store about 60-70% of the body’s blood at any given time. The inclusion of valves within the venous structure is a critical feature that prevents the backflow of blood, especially when it comes to moving blood against gravity, such as in the legs. These valves ensure that blood flows in one direction toward the heart, which is particularly important given that venous return is aided by skeletal muscle contractions and respiratory movements. This structural difference emphasizes veins' role in the circulatory system alongside their adaptation to function effectively under lower pressure conditions compared to arteries. The presence of valves is vital in maintaining blood flow and preventing pooling, which can lead to complications such as varicose veins.