Renal Lecture 1 Spring 08

7/29/2019 Renal Lecture 1 Spring 08

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Renal Physiology

Dr. April Strader

Course: PHYS 410-

MWF 8-9am

Chapters -3, 32-39

Office # 453-1533

Email: [email protected]

Office hours:

Life Science III Room 2066

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mailto:[email protected]:[email protected]


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Lecture 1

Objectives - Body Water Spaces

1. Learn the approximate volumes of total body water, extracellular,intracellular, interstitual and plasma volumes.

2. Describe how determining the volume of distribution of varioussubstances can be used to measure the volumes of the above bodywater spaces.

3. Given appropriate data, calculate the volume of distribution of asubstance.

4. Describe the principles which govern the distribution of fluid betweenthe intracellular and extracellular compartments.

5. Describe the effects of drinking water, or the intravenous infusion of

saline solutions of different osmolalities on the volumes and osmolalitiesof various body fluid spaces.

6. Outline the forces which govern the distribution of fluid betweenplasma and interstitial fluid.

7. Define edema and explain the mechanism by which it develops invarious pathological situations.

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1. Total Human Body Water Spaces*

Total Body Water (TBW) 42 L

(60% of Body Weight)

[ example for 70kg male with 45% hematocrit]

Table 3-1 p.51

Intracellular Fluid -25 L*Extracellular Fluid 17 L

Blood Plasma 3 L Interstitial Fluid 13 L Transcellular Fluid -1 L

(does not include the

2.5L of cellular elements ofBlood; cells, platelets, etc)

Total Blood Volume = 5.5L

Dense connective tissue,

cartilage and tendons, andbone matrix.

Synovial fluid in joints and CSF. Does

NOT include fluids that are consideredoutisde body such as urine in bladder.

Fluid within all body cells.


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1. Intracellular and Extracellular Fluids

42 LITERS Fig. 3-1; p.51

*25L17L


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2. Determining the Volume of Distribution of

Substances to Measure Volumes of Body

Water Spaces.

*

Markers for body water spaces

Body water space Markers

Total body water T20, D20

Extracellular water inulin (NOT insulin)

Plasma 125I albumin,51Cr erythrocytes,

Evans blue (binds to

albumin)

nib

Some spaces you cannot measure with markers and need to be calculated bysubtraction.

Intracellular water = Total Body water Extracellular water

Interstitial water (extravascular water) = Extracellular water- Plasma


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3. Given the appropriate data, calculate the

volume of distribution of a substance.

V1 = volume injected V2 = volume of distribution

C1 = concentration injected C2 = final concentration

After injection, allow time for equilibration:

V2(volume of dist.) = V1 x C1C2


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3. Eg. Calculate the Extravascular Extracellular

Volume of a Patient Using an infusion of inulin.

1 mM of inulin is intravenously infused into your patient in 100 ml ofphysiological saline. Inulin cannot enter cells, but can diffuse freely acrossblood vessel walls and therefore distributes in the extravascularextracellular space. The final inulin concentration in blood plasma afterequilibrium (and accounting for excretion in urine) is 7.7M.

What is the Extracellular Volume of the Patient (in liters)?

What is the Extravascular Extracellular Volume (in liters)?

Using the equation: C1xV1 = C2xV2

C1 = 1mM C2 = 7.7 M

V1 = 100ml V2 = ?


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( 1 mM ) x ( 100ml ) = ( 0.0077 mM ) x V2

C1 V1 C2 V2

V2 = 12, 987 ml ( or approx. 13 L)

This is the Extracellular Volume.

To find Extravascular Extracellular Volume, remember, plasma

volume = 3L , therefore, this volume is : 13 L 3 L = 10 L

3.


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Intracellular and Extracellular Fluids

42 LITERS Fig. 3-1; p.51

*25L17L


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What factors determine the distribution of fluid

between the intracellular and extracellular

compartments.

Extracellular Fluid (ECF) vs. Intracellular Fluid (ICF)

-plasma

-interstitial fluid (IF)

Table 3-2 and Figure 3-1 (p. 51-52) B&B

-Solute concentrations vary dramatically between ECF and ICF.-The plasma and the interstitial fluid have very similar composition (solutes).

-The major difference between plasma and interstitial fluid is plasma proteins.

HOWEVER, the Osmolality of the ECF and the ICF are the same!!!

Osmolality = total concentration of ALL particles that are in a solution

1. OSMOLALITY


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2. ELECTRONEUTRALITY

All solutions must respect the principle of bulk electroneutrality:

the number of positive charges in the solution must equal the negative charges(Table 3-2) p.52

Adding up the cytosolic [Na+] and [K+] we see that the sum GREATLY exceeds

the sum of the [Cl-] and [HCO3-] ions. The excess positive charge is balanced by

the negative charge on intracellular proteins and smaller anions and inorganic

phosphates. (p. 53-54)

4.


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In general, particles move according to concentration (osmolality)

and electrochemical ( ) gradients.

Water movement is PASSIVE and moves from low osmolality to high osmolality.

p. 54

The actual transport of solutes is very complex (including transporters and pumps)

and will be covered in more detail later, but for now, remember that NaCl is largely

excluded from the intracellular compartment.

4.


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5. Describe the effects of drinking water, or the

intravenous infusion of saline solutions of different

osmolalities on the volumes and osmolalities of

various body fluid spaces.

EC vol. IC vol. EC osm. IC osm.

Isotonic saline

Water

Hypertonic Saline

Hypotonic saline

* Think these through, dont memorize it! Page 79. (study figure 3-17)


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6. Outline the forces which govern thedistribution of fluid between plasma andinterstitial fluid.

Starling ForcesStarlings law of the Capillary

Pc = hydrostatic pressure of capillary

c = protein (oncotic) pressure of capillary

Pi= hydrostatic pressure of interstitual fluid

i = protein osmotic (oncotic) pressure of the interstitual fluid

Kf= hydraulic conductance of capillary (ml/min)

Net movement out of capillary into interstitium (ml/min) = Kf[ [(Pc Pi) (ci)]

Basically, movement is governed by (hydrostatic pressure protein (oncotic) pressure)


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5.

Filtration = when fluid moves OUT of a capillary

Absorption = when fluid moves INTO a capillary

FIND THE NET PRESSURE FOR EACH SCENARIO

A. Net Filtration B. Net Absorption

Pc c Pc c

capillary capillary

+30

-1

Pi+26

+3

i+25

+3

i

+32Pi

-1

* Assume that Kfequals 1.


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5.

Filtration = when fluid moves OUT of a capillary

Absorption = when fluid moves INTO a capillary

FIND THE NET PRESSURE FOR EACH SCENARIO

A. Net Filtration = +8mmHg B. Net Absorption = -5mmHg

Pc c Pc c

capillary capillary

+30

-1

Pi+26

+3

i+25

+3

i

+32Pi

-1

* Assume that Kfequals 1.


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Lymph

The lymphatic capillaries are responsible for

returning interstitial fluid and proteins to the vascular

compartment.

-one-way flap valves permits fluid and protein to enter,not leave.

-lymph capillaries merge into large thoracic duct which

empties into the large veins.

-lymph vessels have smooth muscle for movement andsurrounding skeletal muscle contractions.


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7. Define edema and explain the mechanism bywhich it develops in various pathologicalsituations.

EDEMA

Accumulation of fluid in interstitial space (due to filtration

out of the capillaries), usually caused by a disruption in

Starling forces, that exceeds the ability of lymphatics to

return it to the circulation (p. 472-473)


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7. Various examples of Edema

Formation

Pc (Arteriolar dilation, venous constriction, heart failure)

CAUSE EXAMPLE

c (decreased plasma protein concentration, severe liverfailure, nephrotic syndrome loss of protein in urine)

Kf

Burns

Inflammation (release of histamines or cytokines)

Impaired

Lymphatic drainage

Standing, parasitic infection of lymph nodes (filariasis)


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EDEMA FROM THE NEPHROTIC SYNDROME


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Kwashiorkorthe one who is displaced

-Severe protein deficiency and malnutrition

-Edema results from decreased plasma proteins

(decreased albumin in blood).

7.
http://www.answers.com/topic/kwashiorkor-6180-jpg


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FILARIASIS

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Renal Lecture 1 Spring 08