Which of the following statements regarding blood and osmotic pressure at the capillaries is correct?

1 - The arterial end of the capillaries has the highest blood pressure because blood is being forced from the heart to the capillary bed.

2 - The veinous end of the capillary has the highest osmotic pressure because of the difference in carbon dioxide and oxygen concentrations between the capillaries and tissue.

3 - The arterial end of the capillary has the highest osmotic pressure because of the difference in carbon dioxide and oxygen concentrations between the capillaries and tissue.

4 - The veinous end of the capillaries has the highest blood pressure because blood is being forced from the heart to the capillary bed.

5 - Both A and B are correct.

5 - Both A and B are correct.

Blood pressure or hydrostatic pressure is the primary force that transports blood between the capillaries and tissues. Capillary blood pressure or capillary hydrostatic pressure-CHP or arteries is the force that drives blood out of capillaries and into the tissues. Hydrostatic pressure of interstitial fluid is called the interstitial fluid hydrostatic pressure - IFHP. Since the CHP is higher than IFHP fluid moves from the capillary and into the interstitial fluid via process called filtration.

Osmotic pressure or oncotic pressure is the movement of fluid from the interstitial fluid back into the capillaries and it is determined by osmotic concentration gradients. Since osmotic pressure is higher in vein capillaries than in the interstitial fluid, the fluid moves back into the capillary via the process called reabsorption.