Unit Five: The Body Fluids and Kidneys

Chapter 25: The Body Compartments: Extracellular and

Intracellular Fluids; Edema

Guyton and Hall, Textbook of Medical Physiology, 12th edition

Balance of Fluid Intake and Output

• Steady-State Balance

a. Daily intake of waterb. Daily loss of water-insensible water lossc. Fluid loss in sweatd. Water loss in fecese. Water loss by the kidneys

Normal Prolonged Heavy

Exercise

Intake

Fluids ingested 2100 ?

From metabolism

200 200

Total Intake 2300 ?

Output

Insensible-skin 350 350

Insensible-lungs

350 650

Sweat 100 5000

Feces 100 100

Urine 1400 500

Total Output 2300 6600

Table 25.1 Daily Intake and Output of Water (ml/day)

Body Fluid Compartments

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

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

Compartments (cont.)

• Intracellular Fluid Compartment

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

b. Concentration of substances is similar from cellto cell

Compartments (cont.)

• 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

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)

Constituents of Extra- and Intracellular Fluids

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

Fig. 25.2 Nonelectrolytes of the plasma

Constituents of Extra- and Intracellular Fluids

Plasma (mOsm/L of

Water

Interstitial (mOsm/L of

Water

Intracellular (mOsm/L of

Water

Sodium 142 139 14

Potassium 4.2 4.0 140

Calcium 1.3 1.2 0

Magnesium 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

Constituents of Extra- and Intracellular Fluids

Plasma (mOsm/L of

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

Hexose monophosphate

3.7

Glucose 5.6 5.6

Protein 1.2 0.2 4

Urea 4 4 4

Others 4.8 3.9 10

Total mOsm/L 301.8 300.8 301.2

Corrected osmolar activity

282 281 281

Total Osmotic Pressure (37 C)

5443 5423 5423

Table 25.2 Osmolar substances in extracellular and intracellular fluids

Basic Principles of Osmosis and Osmotic Pressure

• Osmosis is the net diffusion of water across a selectively permeable membrane from a region of high water concentration to one that has a lower water concentration.

• Rate of diffusion of water is called the rate of osmosis.

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 active

particles in a solution rather than to the molar

concentration

Osmolality vs. Osmolarity

• Osmolality = osmoles/kg of water

• Osmolarity = osmoles/L of solution

Osmotic Equilibrium

• Isotonic-occurs if the water concentration of both intra-

cellular and extracellular fluid is the same; cells do

shrink or swell

• Hypotonic-occurs if the water concentration is lower

inside the cell (solutes are higher inside) and

the cell will swell and possibly lyse

• Hypertonic-occurs if the water concentration is

higher inside the cell (solutes are lower inside)

and the cell shrivels (crenates); water flows out

of the cell

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

Equilibrium (cont.)

• Isosmotic-solutions with an osmolarity the same as the cell

• Hyperosmotic-solutions with a higher osmolarity

• Hyposmotic-solutions with a lower osmolarity

Volume and Osmolality in Abnormal States

• Effect of adding saline to extracellular fluid

• Hyponatremia

• Hyperantremia

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)