Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Chapter 9 Water

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Objectives Describe functions of water in body Explain fluid balance and its maintenance Name causes and consequences of water depletion Give some causes and consequences of positive fluid balance Describe acid-base balance in human body

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Facts Humans can live approximately 30 to 45 days without food but only 10 to 14 days without water Present in all body cells 50 to 60 percent of body weight of normal adults –Percentage highest in newborns and decreases with age (continues)

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Facts Two basic compartments: –Intracellular fluid (ICF) Within cells 65 percent of total body fluid –Extracellular fluid (ECF) Outside cells 35 percent of total body fluid Found in intravascular fluid (in bloodstream), interstitial fluid (between cells), and glandular secretions

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Functions Major component of blood plasma Solvent and transport for nutrients and waste products Essential component for hydrolysis and metabolism (continues)

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Functions Lubricant in joints and digestion Body coolant through perspiration Shock absorber

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Sources Best: –Drinking water Second-best: –Other beverages Other: –Fruits, vegetables, soups, milk, and gelatin desserts Energy metabolism produces water

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Estimated Daily Fluid Intake for an Adult Ingested liquids: –1,500 mL Water in foods: –700 mL Water from oxidation: –200 mL Total = 2,400 mL

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Fluid and Electrolyte Balance Electrolytes measured in milliequivalents (mEq/L) Water losses must be replaced in volume and electrolyte content Sensible water loss –Noticeable –Water lost through urine (continues)

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Fluid and Electrolyte Balance Insensible water loss –Unnoticeable –Water lost through feces, perspiration, and respiration Solute –Substance dissolved in solution Osmosis –Water flows from side with lesser amount of solute to side with greater solute concentration (continues)

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Fluid and Electrolyte Balance Potassium, sodium, and chloride maintain balance between ICFs and ECFs Potassium –Principal electrolyte in ICF Sodium –Principal electrolyte in ECF (continues)

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Fluid and Electrolyte Balance Osmolality –Measures particles in solution When electrolytes in ECF increase, ICF moves to ECF to equalize concentration of electrolytes on both sides of membrane –Reduces amount of water in cells (continues)

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Fluid and Electrolyte Balance Hypothalamus stimulates pituitary gland to excrete antidiuretic hormone (ADH) ADH causes kidneys to reabsorb water Thirst causes healthy person to drink fluids When sodium in ECF reduced, water flows from ECF into cells –Causes cellular edema (continues)

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Fluid and Electrolyte Balance Adrenal glands secrete aldosterone –Triggers kidneys to increase amount of sodium reabsorbed When sodium replaced in ECF, excess water moves back to ECF –Relieves edema (continues)

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Fluid and Electrolyte Balance Amount of water use varies –Depends on age, size, activity, environmental temperature, and physical condition Average adult requirement: –1 milliliter (mL) for every calorie of food consumed

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Stop and Share Consider the following question: –How many glasses of fluid would be required for an adult eating 1,800 kilocalories per day? (continues)

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Stop and Share 1 mL × 1,800 calories = 1,800 cubic centimeters (cc) 1,800 cc  240 ounces (oz) = 7.5 glasses of water Recommended for adults to drink eight 8-oz glasses of fluid per day (continues)

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Stop and Share Increased requirements during youth, fever, diarrhea, unusual perspiration, and hyperthyroidism

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Dehydration Occurs when amount of water in body inadequate Caused by inadequate intake or abnormal loss –Loss can occur from severe diarrhea, vomiting, hemorrhage, burns, diabetes mellitus, excessive perspiration, excessive urination, or use of certain medications (e.g., diuretics) (continues)

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Dehydration Symptoms: –Low blood pressure, thirst, dry skin, fever, and mental disorientation As water lost, electrolytes also lost Treatment: –Replacement of electrolytes and fluids (continues)

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Dehydration 10 percent loss of body water can cause serious problems 20 percent loss of body water can cause circulatory failure and death Blood volume and nutrient absorption reduced (continues)

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Dehydration Kidney function upset Infants at high risk for dehydration during fever, vomiting, and diarrhea Treatment may involve intravenous (IV) fluids (continues)

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Dehydration Thirst sensation lags behind body’s need for water –Especially in elderly, children, athletes, and ill –Feeling thirsty not reliable indicator of when body needs water Prevention: –Drink fluids throughout day (continues)

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Dehydration Failure to replace water lost through perspiration could lead to one of four stages of heat illness: 1.Heat fatigue 2.Heat cramp 3.Heat exhaustion 4.Heat stroke

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Signs of Dehydration Health history reveals inadequate intake of fluids Decrease in urine output Weight loss Sunken eyes (continues)

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Signs of Dehydration Increased furrows and fissures on tongue Dry oral mucous membranes Decreased skin turgor Changes in neurological status

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Excess Water Accumulation Positive water balance –More water taken in than excreted Results in edema May be caused by hypothyroidism, congestive heart failure, hypoproteinemia, some infections, some cancers, and some renal conditions Fluids and sodium may be restricted

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Acid-Base Balance Regulation of hydrogen ions Acid gives off hydrogen ions Base picks up hydrogen ions Acidic substances have pH of 1 to 7 Alkaline substances have pH of 7 to 14 pH of 7 considered neutral (continues)

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Acid-Base Balance Blood plasma has pH of 7.35 to 7.45 Intracellular fluid has pH of 6.8 Kidneys maintain acid-base balance What person eats affects acidity of urine –Not of body

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Buffer Systems Regulate hydrogen ion content in body fluids Mixture of weak acid and strong base Normal buffer system ratio of base to acid: –20:1 Carbonic acid and sodium bicarbonate form body’s main buffer system (continues)

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Buffer Systems Carbonic acid moves easily to buffer strong alkali Sodium bicarbonate moves easily to buffer strong acid Amounts easily adjusted by lungs and kidneys to suit body’s needs (continues)

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Buffer Systems End products of metabolism: –Carbon dioxide and water Together, can form carbonic acid Medulla oblongata in brain causes breathing rate to increase if amount of carbon dioxide more concentrated than should be –Increases rate at which body rids itself of carbon dioxide (continues)

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Buffer Systems Excess sodium bicarbonate excreted via kidneys Kidneys can excrete urine from pH of 4.5 to 8 pH of average urine: –6

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Acidosis and Alkalosis Acidosis can be caused by renal failure, uncontrolled diabetes mellitus, starvation, or severe diarrhea Alkalosis can occur when body has suffered loss of hydrochloric acid from severe vomiting or has ingested too much alkali (e.g., too many antacid tablets)

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Stop and Share Consider the following scenario: –A client is unhappy with her low-sodium, fluid-restricted diet. How can you best help her? (continues)

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Stop and Share Discuss realistic ways of planning menus –Base menus on good nutrition and her normal habits and desires Review her former diet with her –Point out high-salt and high-liquid foods –Present alternative foods in positive manner

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Conclusion Water –Component of all tissues –Solvent for nutrients and body wastes Provides transport for both Essential for the following: –Hydrolysis –Lubrication –Maintenance of normal temperature (continues)

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Conclusion Best sources: –Water, beverages, fruits, vegetables, soups, and water- based desserts Dehydration can result from lack of water Positive water balance –Excess accumulation of water in body (continues)

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Conclusion Acid-base balance –Regulation of hydrogen ions in body Healthy people have intricate maintenance systems for fluid, electrolytes, and acid-base balance