Which of the following assists in returning the blood to the heart through the veins? A. valves in the veins, the effect of breathing, gravity. B. valves in the veins, the effect of breathing, squashing action of muscles, gravity. C. the effect of gravity, the pumping action of the heart. D. the effect of breathing, squashing action of muscles, the right ventricle.
Option B. valves in the veins, the effect of breathing, squashing action of muscles, gravity assist in returning the blood the heart through the veins.
One of the following does NOT contribute to peripheral resistance. Which one? A. heart rate. B. blood viscosity. C. diameter of blood vessels. D. length of blood vessels
