THE THE MICROCIRCULATION.MICROCIRCULATION.MAIN CONCEPTSMAIN CONCEPTSGuido E. Santacana Ph.D.Guido E. Santacana Ph.D.
ProfessorProfessor
Dept. of PhysiologyDept. of Physiology
MICROCIRCULATIONMICROCIRCULATION STRUCTURESTRUCTURE LAW OF LAPLACELAW OF LAPLACE TRANSCAPILLARY EXCHANGETRANSCAPILLARY EXCHANGE STARLING’S HYPOTHESISSTARLING’S HYPOTHESIS LYMPHATICSLYMPHATICS
Structure of the Structure of the MicrocirculationMicrocirculation
Smoothmuscle
Arteriole
Venule
Metarteriole
Capillary
Endothelial cells
Precapillarysphincters
Ultrastructure of a Ultrastructure of a CapillaryCapillary
Lumen
Intracellular channels
Endothelial cell 1
Endothelial cell 2
Basement membrane
Nucleus
Intercellular cleft
5-10 m
LAW OF LAPLACELAW OF LAPLACE
T = P x r/wt
Tension = Pressure x Radius / wall thickness
Why do the capillaries in our feet don’t just burst from thepressure (about 100mmHg)?
How does Laplace Work?How does Laplace Work?
Less wall tension with Less wall tension with smaller radius?smaller radius?
FLOW AND DIFFUSION LIMITED FLOW AND DIFFUSION LIMITED TRANSPORTTRANSPORT
PARTICLE SIZEAND FLOW
CELL
FLOW LIMITED PARTICLE SIZE &DISTANCE
CELL
DIFFUSION LIMITED
REFLECTION COEFFICIENTREFLECTION COEFFICIENT
oncotic pressure = o RT (Ci - Co)
water=0 albumin=1
RT= gas and temperature constantsCi= concentration insideCo= concentration outside
REFLECTION COEFFICIENT = ACTUAL OSMOTIC FLOW/ THEORETICAL
CAPILLARY FILTRATIONCAPILLARY FILTRATION
HYDROSTATICFORCES
OSMOTIC FORCES
ARTERIAL PRESSUREVENOUS PRESSUREPRE-POST CAPILLARY RES.INTERSTITIAL FLUID PRESSURE
ONCOTIC PRESSURE
ALBUMIN
BALANCESTARLING’S HYPOTHESIS
Qf = k (Pc + i) - (Pi + p)
Graphic Representation Graphic Representation of Capillary Filtrationof Capillary Filtration
Capillary Filtration in Capillary Filtration in Various Clinical ConditionsVarious Clinical Conditions
A B
C D
What I cannot forget What I cannot forget about Microcirculation about Microcirculation
Four Forces known as Starling ForcesDetermine Fluid Movement Across the Capillary Membranes.
Pc= Capillary Pressure Tends to move fluid out of the capillaryPi= 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))
More things that I cannot More things that I cannot forget about the forget about the microcirculationmicrocirculation
EDEMA or excess fluid outflow into the interstitium is commonlycaused 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)
Pitting Edema of the FeetPitting Edema of the Feet
A Pit forms where theskin is pressured. It mayremain there for a few minutes
The Lymphatic SystemThe Lymphatic System
Elephantiasis or Elephantiasis or Lymphatic FilariasisLymphatic Filariasis