Each of the following mechanisms plays a role in the return of blood to the heart via veins EXCEPT which one?
A. osmotic pressure exerted by plasma proteins in the blood
B. squeezing action of skeletal muscles
C. valves that permit the one-way flow of blood returning to the heart and prevent backflow
D. pressure changes in the abdominal and thoracic cavities associated with breathing
Answer:A
Each of the following mechanisms plays a role in the return of blood to the heart via veins EXCEPT which one?
A. osmotic pressure exerted by plasma proteins in the blood B. squeezing action of skeletal muscles C. valves that permit the one-way flow of blood returning to the heart and prevent backflow D. pressure changes in the abdominal and thoracic cavities associated with breathing