Question

Which of the following statements is true? Select all that apply. Capillaries have a higher resistance to flow than either arteries or veins. Blood travels at a higher velocity in arteries than in veins. The volume of blood flow in the arteries and arterioles is greater than the volume of blood flow through the capillaries. The total cross-sectional area of the capillaries is greater than the total cross-sectional area of the venules and veins. Blood pressure is higher in arteries than in veins.

Answer 1

Answer:

1. Blood travels at a higher velocity in arteries than in veins.
2. The volume of blood flow in the arteries and arterioles is greater than the volume of blood flow through the capillaries
3. Blood pressure is higher in arteries than in veins.
4. The total cross-sectional area of the capillaries is greater than the total cross-sectional area of the venules and veins

Explanation:

The lumen of arteries is larger than that of arterioles and capillaries. However, even though they have a smaller lumen compared to veins, their walls are thicker to bear the pressure of the blood as it is pumped by the heart to the tissues. Therefore the blood pressure and velocity of blood in arteries (that pump blood away from the heart) is higher than in capillaries and veins. Veins take blood back to the heart from tissues hence this blood is under lower pressure and velocity. This is why veins have valves to prevent the back-flow of blood against gravity.

Due to the large cross-section area of capillaries the blood flow is here is slower hence giving time for blood to linger a bit so there is an exchange of materials between the blood plasma and the interstitial fluids that nourish the cells.