What is the pulling effect that draws water into the vascular space within capillaries?

What is the pulling effect that draws water into the vascular space within capillaries?

• A. Hydrostatic pressure
• B. Oncotic pressure
• C. Plasma osmotic
• D. Interstitial pressure

Answer: (C)

Water movement across capillary walls follows Starling forces. The pulling effect that draws water back into the vascular space is plasma oncotic pressure—the colloid osmotic pressure generated by plasma proteins (mainly albumin). Because these proteins remain in the blood, they create a higher osmotic pressure inside the capillary than in the surrounding interstitial fluid, pulling fluid inward. By contrast, hydrostatic pressure pushes fluid out of the capillary into the interstitial space, so the balance between these forces determines filtration versus reabsorption.

Water movement across capillary walls follows Starling forces. The pulling effect that draws water back into the vascular space is plasma oncotic pressure—the colloid osmotic pressure generated by plasma proteins (mainly albumin). Because these proteins remain in the blood, they create a higher osmotic pressure inside the capillary than in the surrounding interstitial fluid, pulling fluid inward. By contrast, hydrostatic pressure pushes fluid out of the capillary into the interstitial space, so the balance between these forces determines filtration versus reabsorption.