renal physiology . ch25

8/13/2019 renal physiology . ch25

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Balance of Fluid Intake and Output

Steady-State Balance

a. Daily intake of waterb. Daily loss of water-insensible water loss

c. Fluid loss in sweatd. Water loss in fecese. Water loss by the kidneys


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Body Fluid Compartments

Fig. 25.1 Summary of body fluid regulation, including the major body fluid compartments


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Compartments (cont.)

Body Fluid Compartments

a. Intracellularb. Extracellular-interstitial fluid and blood plasmac. Transcellular-fluids in the synovial, peritoneal,

pericardial, intraocular spaces, and the CSFd. Total body water for men is about 60% and 50%

for womene. Varies with age, gender, and degree of obesity


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Intracellular Fluid Compartment

a. Constitutes about 40% of the fluid in the averageperson

b. Concentration of substances is similar from cellto cell


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Extracellular Fluid Compartment

a. Interstitial fluid-makes up about 75% of the fluidb. Blood plasma-makes up 25% of the fluidc. Only real difference between the two types is the

protein composition of the plasma


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Blood Volume

Blood Volume

a. Makes up about 7% of the body weight (5 L)b. 60% plasma and 40% cellsc. Percentages vary according to gender, weight, etc.

Hematocrit

a. Red blood cell fraction of the bloodb. 96% accurate because you cannot pack the cells

completelyc. Males (o.40) and females (o.30)


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Constituents of Extra- and Intracellular Fluids

Fig. 25.2 Major cations and anions of intracellular andextracellular fluids.

Fig. 25.2 Nonelectrolytes of the plasma


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Plasma (mOsm/L of Water

Interstitial (mOsm/Lof Water

Intracellular(mOsm/L of Water

Sodium 142 139 14

Potassium 4.2 4.0 140

Calcium 1.3 1.2 0Magnesium 0.8 0.7 20

Chlorine 108 108 4

Bicarbonate 24 28.3 10

Phosphate 2 2 11

Sulfate 0.5 0.5 1

Phosphocreatine 45

Carnosine 14

Amino acids 2 2 8

Table 25.2 Osmolar substances in extracellular and intracellular fluids


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Plasma (mOsm/Lof Water

Interstitial(mOsm/L of Water

Intracellular(mOsm/L of Water

Creatine 0.2 0.2 9

Lactate 1.2 1.2 1.5

ATP 5

Hexosemonophosphate

3.7

Glucose 5.6 5.6

Protein 1.2 0.2 4

Urea 4 4 4Others 4.8 3.9 10

Total mOsm/L 301.8 300.8 301.2

Corrected osmolaractivity

282 281 281

Total OsmoticPressure (37 C) 5443 5423 5423

Table 25.2 Osmolar substances in extracellular and intracellular fluids


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Basic Principles of Osmosis and Osmotic Pressure

Osmosis is the net diffusion of water across aselectively permeable membrane from aregion of high water concentration to one

that has a lower water concentration. Rate of diffusion of water is called the rate of

osmosis.


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Moles vs. Osmoles

Osmoles-the total number of particles in a solution

One osmole is equal to 1 mole of solute particles

Osmole refers to the number of osmotically activeparticles in a solution rather than to the molarconcentration


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Osmotic Equilibrium

Isotonic- occurs if the water concentration of both intra-cellular and extracellular fluid is the same; cells doshrink or swell

Hypotonic- occurs if the water concentration is lowerinside the cell (solutes are higher inside) andthe cell will swell and possibly lyse

Hypertonic- occurs if the water concentration ishigher inside the cell (solutes are lower inside)and the cell shrivels (crenates); water flows outof the cell


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Fig. 25.5 Effects of isotonic, hypotonic, and hypertonic solutions on cell volume


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Equilibrium (cont.)

Isosmotic- solutions with an osmolarity the same as the cell

Hyperosmotic- solutions with a higher osmolarity

Hyposmotic- solutions with a lower osmolarity


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Volume and Osmolality in Abnormal States

Effect of adding saline to extracellular fluid

Hyponatremia

Hyperantremia


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Edema

Intracellular Edema

a. Hyponatremiab. Depression of metabolic systems of tissuesc. Lack of adequate nutrition to the cells

Extracellular Edema

a. Abnormal leakage of fluid from plasmab. Failure of the lymphatics to return the fluid

(lymphedema)

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renal physiology . ch25