water & the body fluids 60% of adult body weight -water makes up ¾ of the weight of lean tissue...
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Water & The Body Fluids
• 60% of adult body weight-Water makes up ¾ of the
weight of lean tissue-Water makes up ¼ of the
weight of fat
Copyright 2005 Wadsworth Group, a division of Thomson LearningCopyright 2005 Wadsworth Group, a division of Thomson Learning
Water & Body Fluids• Functions of water:
– Transport– Structural support for molecules– Participates in metabolic reactions– Solvent– Lubricant & shock absorber– Body temperature regulation– Maintains blood volume & blood
pressure
Water & The Body Fluids
• Water balance – Intracellular fluid-within the cells– Extracellular fluid-outside the cells
•Interstitial fluid•Plasma
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One Cell And Its
Associated Fluids
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Water & Body Fluids• Water Balance
-Intake/output = 2.5 liters/day-Regulated by hypothalamus & kidneys-Carefully controlled by:
1. Intake (liquid, foods, metabolic water) affected by thirst & satiety
2. Output (losses via kidneys, skin, lungs, feces) affected by blood salts, volume & blood pressure
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How The Body Regulates Blood Volume
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Water & Body Fluids• Recommendations:
-Needs vary according to type of food eaten, temperature, humidity, activity level, etc.
-General rule: 1–1.5 ml/kcal expended Example: if 2000 kcal “burned” then
2-3 liters suggested; >8 cups from fluids and the rest comes from food & metabolic water
-Urine should be pale yellow-Caffeine & alcohol act as diuretics so not
good water substitutes
Fluid & Electrolyte Balance
• Electrolytes – salts that dissolve in water, forming ions
• Dissociation of salt in water– Ions
•Cations- + charged particles•Anions- - charged particles
– Electrolyte solution
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Copyright 2005 Wadsworth Group, a division of Thomson LearningCopyright 2005 Wadsworth Group, a division of Thomson Learning
Water Dissolves SaltsAnd Follows Electrolytes
Fluid & Electrolyte Balance • Electrolytes attract water - affects fluid
distribution in the body by osmosis • Water follows electrolytes
– Solutes– Osmosis– Osmotic pressure
• Electrolyte concentration regulated by kidneys
• Electrolytes & proteins act as buffers to maintain the pH of body fluids – acid/base balance
Copyright 2005 Wadsworth Group, a division of Thomson LearningCopyright 2005 Wadsworth Group, a division of Thomson Learning
Copyright 2005 Wadsworth Group, a division of Thomson LearningCopyright 2005 Wadsworth Group, a division of Thomson Learning
Acid-Base Balance
• pH• Regulation by the buffers
– Bicarbonate– Carbonic acid
• Regulation by the kidneys• Regulation by the lungs
Copyright 2005 Wadsworth Group, a division of Thomson LearningCopyright 2005 Wadsworth Group, a division of Thomson Learning
Copyright 2005 Wadsworth Group, a division of Thomson LearningCopyright 2005 Wadsworth Group, a division of Thomson Learning
Fluid & Electrolyte Imbalance• Replacing lost
fluids and electrolytes– Oral
rehydration therapy (ORT)-a simple solution of sugar, salt and water
Copyright 2005 Wadsworth Group, a division of Thomson LearningCopyright 2005 Wadsworth Group, a division of Thomson Learning
Fluid & Electrolyte Imbalance
• Sodium and chloride most easily lost• Different solutes lost by different
routes• Rapid fluid/electrolyte loss, i.e.
vomiting, diarrhea, heavy sweating, fever, burns, wounds = medical emergency
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