Which general principle describes how blood flows through the circulatory system?

Which general principle describes how blood flows through the circulatory system?

• A. From higher to lower pressure, with pressure falling progressively as it moves through the body
• B. From lower to higher pressure, with pressures increasing along the path
• C. Pressure remains constant throughout the circulation
• D. Flow is independent of pressure differences

Answer: (A)

Blood flow in the circulatory system is driven by a pressure gradient. The heart generates higher pressure in the arteries, especially near the left ventricle, and as blood moves through the vessels—the arteries, arterioles, capillaries, venules, and veins—the pressure gradually falls due to friction and resistance to flow. Because blood moves from regions of higher pressure to regions of lower pressure, overall circulation proceeds forward continuously. This concept can be summarized by flow being proportional to the pressure difference and inversely proportional to vascular resistance. If flow were from lower to higher pressure, or if pressure stayed the same everywhere, or if flow were independent of pressure differences, there would be no driving force for circulation, which contradicts how the cardiovascular system actually works.

Blood flow in the circulatory system is driven by a pressure gradient. The heart generates higher pressure in the arteries, especially near the left ventricle, and as blood moves through the vessels—the arteries, arterioles, capillaries, venules, and veins—the pressure gradually falls due to friction and resistance to flow. Because blood moves from regions of higher pressure to regions of lower pressure, overall circulation proceeds forward continuously. This concept can be summarized by flow being proportional to the pressure difference and inversely proportional to vascular resistance.

If flow were from lower to higher pressure, or if pressure stayed the same everywhere, or if flow were independent of pressure differences, there would be no driving force for circulation, which contradicts how the cardiovascular system actually works.