In the name of GOD Blood Circulation 3 Dr. Radmanesh

The Microcirculation and vasomotion

Arterioles and Capillaries Figure 8.2

Transendothelial exchange inter-endothelial cell clefts paracellular transcellular vesicles fenestra inter-endothelial cell clefts

Transport Mechanisms Diffusion Intercellular Clefts Plasmalemmal Vesicles “Tight Junctions” (brain) Open Junctions (liver) Fenestra (kidney)

Diffusion through Capillary Membrane This figure illustrates that the permeability of substances through capillary membrane decreases roughly with the logarithm of size.

Fluid Filtration Across Capillaries

NFP= (Pc +if ) – (p + Pif )

Filtration= K * NFP

V = Kf [ ( Pc +if ) – (p + Pif ) ] V= K * NFP

On the arteriole end, the hydrostatic pressure is higher than the oncotic, so there is fluid movement from plasma to interstitium.  The magnitude of this water flow is indicated by the light blue area on the left (downward arrows). On the venule end, the hydrostatic pressure has dropped below the oncotic pressure.  Fluid moves back from the interstitium to the plasma. The magnitude of this reverse flow is indicated by the green area on the right (upward arrows).  

factor that increases interstitial fluid pressure : increases lymph flow Elevated capillary pressure Decreased plasma colloid osmotic pressure Increased interstitial fluid colloid osmotic pressure Increased permeability of the capillaries

Summary of Factors That Determine Lymph Flow (1) the interstitial fluid pressure (2) the activity of the lymphatic pump. the rate of lymph flow is determined by the product of interstitial fluid pressure times the activity of the lymphatic pump.

Causes of Edema Increase capillary pressure Increase capillary permeability Decrease colloidal osmotic pressure Obstruction of lymphatic flow