Hydrostatic pressure: Molecular Transport Mechanisms · 17/12/2016 · 5 Oncotic Pressure Oncotic...
Transcript of Hydrostatic pressure: Molecular Transport Mechanisms · 17/12/2016 · 5 Oncotic Pressure Oncotic...
the approximate fluid volume in with the body mass?Fluid 60 % ICF 40% ECF 20 %1 kg of water = 1 Liter of volume
Pressure1 mm Hg = 133.322 Pa
P = 120 mmHgP= 120×133.322 = 15998.64 Pa
Thepressureintheurinarybladderis25mmHg.ThispressureinkPaisequalto
Hydrostaticpressure:pressureexertedbytheweightoffluid.
Molecular Transport Mechanisms
Diffusionishighlyefficientfor:
Convectionisessentialto:portionoffluidmovedoverlargerdistance
Osmosis
• Osmosis is the diffusion of water across a semi-permeable (or differentially permeable or selectively permeable) membrane.
• Low to high concentration until equilibrium
Osmosis in cellsIf an animal or plant cell is placed in a solution
• Hypertonic solutions are those in which more solute (and hence lower water potential) is present. → Cell will lose water
• Hypotonic solutions are those with less solute (and hence higher water potential) is present. → Cell will gain water
• Isotonic solutions have equal (iso-) concentrations of substances. Water potentials are equal. → no net movement across cell membrane
Osmosis
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Oncotic PressureOncotic pressure (colloid osmotic pressure) is a pressure exerted by proteins (blood plasma).
Because large plasma proteins cannot easily cross through the capillary walls, their effect on the osmotic pressure is balanced out the tendency for fluid to leak out of the capillaries.Example Albumin keeps the fluid from the blood from leaking out into the tissues.
Oncotic Pressure
• The pressure that forces fluid movement into the capillaries from the outside fluid due to concentration differences is called the
• When plasma proteins are reduced, • e.g., proteinuria or from malnutrition, • there will be a reduction in oncotic pressure and an
increase in filtration across the capillary, resulting in excess fluid buildup in the tissues (edema).
Example: Ascitesexcessive accumulation of fluid in the
abdominal cavity
imbalanceofpressurebetweeninsidethecirculationandoutsideliverdisease,cancers,orkidneyfailure.
Periorbital edema peripheral Pitting edema
Example: EdemaCutaneousedema
fluidretention underskin
Example: A cell is placed in a solution. The values of the related pressures are (Table):What is the net pressure in the cell?
Pressure toward outside - inside= ICF Hydrostatic –ICF oncotic – ECF Hydrostatic + ECF oncotic = 20-15-16+8=- 3 mmHg
What is the direction of the net pressure?
HydrostaticPressure
Oncotic Pressure
Intracellular 20 mm Hg 15 mm HgExtracellular 16 mm Hg 8 mm Hg
ECFICF
Thisenvironmentisdescribedas….
Example of pressure balance: Kidney FunctionFiltration of blood in kidneys is example of
balanced pressure
Example:Uponphysicalexamination,anadultmaleappearsseverelydehydrated,hisbloodpressure(BP)is110/50mmHg,pulseis60perminuteandweak,hiscurrentweightis72kg(hisoriginalweightbeforewas80kg).LaboratorytestsareshownintheTable forprotein.
1.Whatisthebloodoncotic pressureofthepatientif1mg/Lofalbuminproduces2mmHgofosmoticpressure?Answer
Plasmaabilitytoabsorbfluidosmotically25mg/L×2mmHg.L/mg=50mmHg
Whatisthedirectionofthispressure?
2.WhatisthenetoncoticpressureICFoncoticpressureis5×2=10mmHgNetoncoticpressure=50-10=40mmHgComparetooriginalvalues?
Palsma (ECF) Cellular (ICF)Albumin (protein) 25mg/L 5mg/L
Albumin(protein) 15mg/L 10mg/L
Normalvaluesare
3.Youhavenoticedthatthepatienthasproducedonly50mlofurine.Assumingthattheintracapsularpressureis0mmHgthenetfiltrationpressure(NFP)inglomeruli(thekidney)is:
capillarybloodpressureintheglomerulusequalsthediastolicbloodpressure=50mmHg
NFP=Capillarybloodpressure– Capillaryoncoticpressure– Intracapasularpressure=50- 50– 0=0mmHg
4.Youhaveinitiatedfluidvolumereplacementtherapywithnormalsaline(NaCl–0.9%)IV(Intravenoustherapy )atarateof3.4litersperhour.InrelationtotheactualfluidvolumelossandyourtreatmenttheECFwillbecome:
hypotonichypertonicor,isotonic
•A 78-year-old female patient with a long history of diabetes •complains of swollen legs (Fig.). •A urine analysis reveals 300 mg/dL of proteins in the urine sample •(normal urine protein concentration is below 0.5 mg/dL). •The patient’s condition is a result of change in:
•Hydrostatic blood pressure•Oncotic pressure•Systolic blood pressure•Static blood pressure
Exercise1 : A cell is placed in a solution. The values of the related pressures are (Table):
Net Pressure =
What is the environment of this solution
Hydrostatic Pressure Oncotic PressureIntracellular 21 mm Hg 9 mm HgExtracellular 19 mm Hg 11mm Hg
Exercise2:Acellisimmersedinasolutionwherethenethydrostaticpressureis0.0mmHg.Duetoconcentrationdifferences,theextracellularoncoticpressureis6mmHgandtheintracellularoncoticpressureis4.5mmHg.Thissolutionenvironmentisconsidered…..
Hint:ICFhydrostaticpressure– ECFhydrostaticpressure=0mmHg