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THE MICROCIRCULATION. MAIN CONCEPTS

THE MICROCIRCULATION. MAIN CONCEPTS. Guido E. Santacana Ph.D. Professor Dept. of Physiology. MICROCIRCULATION. STRUCTURE LAW OF LAPLACE TRANSCAPILLARY EXCHANGE STARLING’S HYPOTHESIS LYMPHATICS. Smooth muscle. Endothelial cells. Arteriole. Precapillary sphincters. Capillary.

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THE MICROCIRCULATION. MAIN CONCEPTS

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  1. THE MICROCIRCULATION.MAIN CONCEPTS Guido E. Santacana Ph.D. Professor Dept. of Physiology

  2. MICROCIRCULATION • STRUCTURE • LAW OF LAPLACE • TRANSCAPILLARY EXCHANGE • STARLING’S HYPOTHESIS • LYMPHATICS

  3. Smooth muscle Endothelial cells Arteriole Precapillary sphincters Capillary Metarteriole Venule Structure of the Microcirculation

  4. Endothelial cell 1 Basement membrane Nucleus 5-10 m Intracellular channels Intercellular cleft Lumen Endothelial cell 2 Ultrastructure of a Capillary

  5. LAW OF LAPLACE Why do the capillaries in our feet don’t just burst from the pressure (about 100mmHg)? T = P x r/wt Tension = Pressure x Radius / wall thickness

  6. How does Laplace Work?

  7. Less wall tension with smaller radius?

  8. DIFFUSION LIMITED PARTICLE SIZE & DISTANCE PARTICLE SIZE AND FLOW CELL CELL FLOW AND DIFFUSION LIMITED TRANSPORT FLOW LIMITED

  9. oncotic pressure = o RT (Ci - Co) albumin=1 water=0 REFLECTION COEFFICIENT RT= gas and temperature constants Ci= concentration inside Co= concentration outside REFLECTION COEFFICIENT = ACTUAL OSMOTIC FLOW/ THEORETICAL

  10. CAPILLARY FILTRATION HYDROSTATIC FORCES OSMOTIC FORCES ONCOTIC PRESSURE ARTERIAL PRESSURE VENOUS PRESSURE PRE-POST CAPILLARY RES. INTERSTITIAL FLUID PRESSURE ALBUMIN BALANCE STARLING’S HYPOTHESIS Qf = k (Pc + i) - (Pi + p)

  11. Graphic Representation of Capillary Filtration

  12. Capillary Filtration in Various Clinical Conditions B A C D

  13. What I cannot forget about Microcirculation Four Forces known as Starling Forces Determine Fluid Movement Across the Capillary Membranes. Pc= Capillary Pressure Tends to move fluid out of the capillary Pi= Interstitial Fluid Pressure Tends to move fluid into the capillary. Πc = Plasma Colloid Osmotic Pressure Tends to cause Osmosis of fluid into capillary. Πi = Interstitial fluid colloid osmotic pressure Tends to cause osmosis of fluid out of the capillary. Net Filtration Pressure = Pnet= ((Pc-Pi) – (Πc- Πi))

  14. More things that I cannot forget about the microcirculation EDEMA or excess fluid outflow into the interstitium is commonly caused by : Capillary Pressure ( Pc ; Heart Failure) Plasma Proteins ( Πc ; Nephrotic Syndrome, liver failure) Capillary Permeability ( Kf ; Toxins, infections, burns) Interstitial Fluid Colloid Osmotic Pressure ( Πi; lymphatic blockage) Net Fluid Flow = Pnet (Kf)

  15. Pitting Edema of the Feet A Pit forms where the skin is pressured. It may remain there for a few minutes

  16. The Lymphatic System

  17. Elephantiasis or Lymphatic Filariasis

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