Chapter 9 Water Copyright 2011 Delmar Cengage Learning

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 Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. (continues)

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 Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. (continues)

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 m. L • Water in foods: – 700 m. L • Water from oxidation: – 200 m. L • Total = 2, 400 m. L Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED.

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

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 Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. (continues)

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

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 Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. (continues)

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 Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. (continues)

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 Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. (continues)

Fluid and Electrolyte Balance • Amount of water use varies – Depends on age, size, activity, environmental temperature, and physical condition • Average adult requirement: – 1 milliliter (m. L) 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? Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. (continues)

Stop and Share • 1 m. L × 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 Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. (continues)

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) Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. (continues)

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

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 Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. (continues)

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

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 Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. (continues)

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

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 p. H of 1 to 7 Alkaline substances have p. H of 7 to 14 p. H of 7 considered neutral Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. (continues)

Acid-Base Balance • • Blood plasma has p. H of 7. 35 to 7. 45 Intracellular fluid has p. H 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 Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. (continues)

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 Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. (continues)

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 Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. (continues)

Buffer Systems • Excess sodium bicarbonate excreted via kidneys • Kidneys can excrete urine from p. H of 4. 5 to 8 • p. H 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? Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. (continues)

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 Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. (continues)

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

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