PowerPoint - Chapter 27 lecture

PowerPoint - Chapter 27 lecture - Chapter 27 FLUIDS,...

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1 Chapter 27 FLUIDS, ELECTROLYTES, AND ACID-BASE HOMEOSTASIS Fluid Compartment and Fluid balance Water is the largest component of the body; 45-75% of total body mass, depending on age and gender Body Fluids constitute: – 60% in adult male of body mass – 55% in adult female of body mass – Infants have the highest water percentage 75% of body mass Fatter people have less water Skeletal muscle tissue is about 65% water Fluid compartments Intracellular (ICF) • The cytosol; two third of the body fluid Extracelluar (ECF) • all other body fluid; one third of the body fluid – 80% interstitial fluid (between the cells) – 20% plasma – Also include lymph, CSF, fluids in joint, eye, endolymph, perilymph, cavities (pleural, peritonum, pericardial)
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2 Barriers separate intracellular fluid from interstitial fluid, and blood plasma Plasma membrane – Selective barrier – Separates intracellular fluid from the surrounding interstitial fluid Blood vessel walls – Separate interstitial fluid from blood plasma – Water and solutes exchange between ISF and plasma happen in the capillaries only Body fluid Body fluid is balanced: – correctly proportioned among the various compartments – depends primarily on electrolyte balance – kidneys excrete excess water (dilute urine) and excess electrolytes (concentrated urine) Osmosis – is the primary means of water movement between intracellular fluid and interstitial fluid b solutes concentration in fluids determines water direction Solutes in body fluids are: – Electrolytes and inorganic compounds that dissociate into ions.
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3 Sources of Body Water Gain and Loss Water gain: – Ingestion of liquid and moist food • main sources of body water (1600 mL water, 700 mL food) • absorbed from the gastrointestinal tract – metabolic water • accounts for 200 mL/ day • Mainly produced in aerobic respiration • smaller portion in dehydration synthesis reactions – Total water gain 2500 mL Water loss: – kidneys excrete about 1500 mL in urine – skin evaporates about 600 mL (400 mL insensible, 200 mL sweat) – lungs exhale about 300 mL as water vapor – gastrointestinal tract eliminates about 100 mL in feces – additional loss in menstruated women – Total loss 2500 mL. water loss of each rout vary depend on the situation ( diarrhea, exertion) Water loss equal water gain Regulation of Body Water Gain Metabolic Water – not regulated – depends on the level of aerobic respiration based on ATP needs Water intake – Regulated – thirst center in the hypothalamus governs the urge to drink. • Increase water loss – decrease volume and an increase in Osmolarity b stimulates thirst center – decrease blood volume b decrease blood pressure b kidneys release renin b angiotensin II b stimulate thirst center – other signals that stimulate thirst » neurons in the mouth detect dryness due to a decreased flow of saliva – Baroreceptors detect low blood pressure in the heart and blood
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PowerPoint - Chapter 27 lecture - Chapter 27 FLUIDS,...

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