Starling Forces

Which variable in the Starling equation represents capillary hydrostatic pressure?

• Pc

• Pi

• πp

• πi

• k

In the Starling framework, which force primarily pulls water into capillaries?

• Plasma oncotic pressure

• Capillary hydrostatic pressure

• Interstitial hydrostatic pressure

• Interstitial oncotic pressure

• Filtration constant

Which expression best represents the net driving pressure for filtration across a capillary wall?

• (Pc + πi) − (Pi + πp)

• (Pc + πp) − (Pi + πi)

• (Pi + πp) − (Pc + πi)

• (πp + πi) − (Pc + Pi)

• (Pc − Pi) − (πp − πi)

If πp decreases due to hypoalbuminemia while other variables remain constant, what is the most likely effect at the capillary level?

• Increased net filtration

• Decreased net filtration

• Increased net absorption

• No change in fluid movement

• Reversal of lymph flow

At the arterial end of a typical systemic capillary, which statement is most accurate?

• Hydrostatic pressure exceeds oncotic pressure

• Oncotic pressure exceeds hydrostatic pressure

• All pressures are approximately equal

• Interstitial pressures dominate exchange

• Filtration constant determines direction

Which change would most directly favor capillary absorption at the venous end?

• Decrease Pc

• Increase Pc

• Decrease πp

• Increase πi

• Increase k

A patient has elevated interstitial fluid oncotic pressure (πi) from extracellular protein leakage. Predict the immediate effect on transcapillary fluid movement.

• Shift toward filtration

• Shift toward absorption

• No net change overall

• Alternating filtration cycles

• Reduced lymphatic drainage

In the Starling equation Qf = k[(Pc + πi) − (Pi + πp)], what does a negative Qf signify under physiological conditions?

• Net absorption into capillary

• Net filtration into interstitium

• Increased capillary permeability

• Increased lymphatic return

• Equal opposing forces at equilibrium

Which process best describes pinocytosis in endothelial cells?

• Nonspecific uptake of extracellular fluid by vesicles

• Selective transport of ions through protein channels

• Active pumping of water via aquaporin proteins

• Bulk flow of plasma driven purely by hydrostatic pressure

Place the steps of vesicular transport across an endothelial cell in the correct order.

• Exocytosis at interstitial side → endocytosis at luminal side → vesicle transit

• Endocytosis at luminal side → vesicle transit across cell → exocytosis at interstitial side

• Vesicle transit across cell → exocytosis at luminal side → endocytosis at interstitial side

• Diffusion across membrane → endocytosis → exocytosis across capillary wall