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

5

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