Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. BODY FLUIDS  Water is most abundant body compound  References to “average” body water volume based on a healthy, nonobese, 70-kg male  Water is-  60% of body weight in males  50% of body weight in females  Volume averages 40 L in a 70-kg male Slid e 2

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. BODY FLUIDS  Variation in total body water is related to:  Total body weight of individual  Fat content of body—the more fat the less water (adipose tissue is low in water content)  Gender—female body has about 10% less water than male body  Age—  in a newborn infant, water may account for 80% of total body weight  In the elderly, water per pound of weight decreases (muscle tissue—high in water—replaced by fat, which is lower in water) Slid e 3

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Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. BODY FLUID COMPARTMENTS  Two major fluid compartments  Extracellular fluid (ECF)  Types:  Plasma  Interstitial fluid (IF)  Miscellaneous—lymph; joint fluids; cerebrospinal fluid; eye humors  Called internal environment of body  Surrounds cells and transports substances to and from them Slid e 5

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. BODY FLUID COMPARTMENTS  Intracellular fluid (ICF)  Largest fluid compartment  Located inside cells  Serves as solvent to facilitate intracellular chemical reactions Slid e 6

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Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Slid e 8

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. MECHANISMS THAT MAINTAIN FLUID BALANCE  Fluid output, mainly urine volume, adjusts to fluid intake  ADH (anti diuretic hormone)  increase kidney tubule reabsorption of sodium and water from tubular urine into blood  increase ECF (and total body fluid) by decreasing urine volume  ECF (extracellular volume) electrolyte concentration  an increase in ECF Na + tends to increase ECF volume by increasing movement of water out of ICF and by increasing ADH secretion  decreases urine volume, and this, in turn, increases ECF volume Slid e 9

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. MECHANISMS THAT MAINTAIN FLUID BALANCE  Capillary blood pressure pushes water out of blood, into IF  Blood protein concentration pulls water into blood from IF  Hence, these two forces regulate plasma and IF volume under usual conditions Slid e 10

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. MECHANISMS THAT MAINTAIN FLUID BALANCE  Importance of electrolytes in body fluids  Electrolytes—compounds that break up or dissociate in water solution into separate particles called ions (e.g., ordinary table salt or sodium chloride)  Ions—the dissociated particles of an electrolyte that carry an electrical charge (e.g., sodium ion [Na + ])  Positively charged ions (e.g., potassium [K + ] and sodium [Na + ])  Negatively charged particles (ions) (e.g., chloride [Cl  ] and bicarbonate [HCO 3  ]) Slid e 11

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. MECHANISMS THAT MAINTAIN FLUID BALANCE  Electrolyte composition of blood plasma  Sodium—most abundant and important positively charged ion of plasma  Normal plasma level—142 mEq/L  Average daily intake (diet)—100 mEq  Chief method of regulation—kidney  Aldosterone increases Na + reabsorption in kidney tubules  Sodium-containing internal secretions (Figure 18-7) Slid e 12

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Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. FLUID IMBALANCES  Dehydration—total volume of body fluids less than normal; IF volume shrinks first, and then if treatment is not given, ICF volume and plasma volume decrease; dehydration occurs when fluid output exceeds intake for an extended period  Overhydration—total volume of body fluids greater than normal; overhydration occurs when fluid intake exceeds output; various factors may cause this (e.g., giving excessive amounts of intravenous fluids or giving them too rapidly may increase intake above output) Slid e 14