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 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 Copyright 2005 Wadsworth Group, a division of Thomson Learning

One Cell And Its Associated Fluids Copyright 2005 Wadsworth Group, a division of Thomson Learning

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

Copyright 2005 Wadsworth Group, a division of Thomson Learning How The Body Regulates Blood Volume

Copyright 2005 Wadsworth Group, a division of Thomson Learning

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 Copyright 2005 Wadsworth Group, a division of Thomson Learning

Water Dissolves Salts And 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 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 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 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 Copyright 2005 Wadsworth Group, a division of Thomson Learning