Introduction Microcirculation capillaries, the smallest blood vessels, are the site of exchange of nutrients, waste products, and fluids capillaries are thin-walled (a single layer of endothelial cells) and allow for the exchange of solutes and gases O2 and CO2 login to view 1 more bullet water-soluble substances e.g., water, glucose, and amino acids diffusion through aqueous clefts between cells login to view 2 more bullets e.g., water, glucose, and amino acids diffusion through aqueous clefts between cells e.g., water, glucose, and amino acids diffusion through aqueous clefts between cells e.g., water, glucose, and amino acids diffusion through aqueous clefts between cells Exchange of Fluids Osmosis is driven by Starling forces (hydrostatic and osmotic pressures) protein contributes to osmotic pressure (noted as oncotic pressure) filtration net fluid out of capillaries into the interstitium absorption net fluid into capillaries from the interstitium Starling equation Jv = Kf [(Pc - Pi) - (πc - πi)] fluid movement is determined by sum of hydrostatic and oncotic pressures variables Kf login to view 2 more bullets Pc login to view 1 more bullet Pi login to view 1 more bullet πc login to view 2 more bullets πi login to view 1 more bullet the magnitude of fluid movement for a given pressure difference determined by hydraulic conductance (Kf, or water permeability) of the capillary wall Edema Edema, or swelling ↑ interstitial fluid volume occurs when interstitial volume > ability of lymphatics to drain it back into circulation from ↑ filtration causes of edema ↑Pc login to view 1 more bullet ↓ πc (↓ plasma proteins) login to view 4 more bullets ↑ Kf (↑ capillary permeability) login to view 2 more bullets ↑ πi login to view 2 more bullets