KAAP221 Lecture Notes - Lecture 24: Osmotic Concentration, Extracellular Fluid, Sweat Gland
11 May 2018
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Lecture 24
• Chapter 25 - fluid, electrolyte, and acid-base balance
• Body composition
• Solids = 40% and water = 60%
• Body water distributed in 2 fluid compartments
• Distinct environments separated by plasma membranes; maintained by active transport
• ICF - cytosolic fluid; most body water found here
• ECF - interstitial fluid and plasma of circulating blood
• Males have greater body water content - greatest variation in ICF, less so in ECF; plasma the same
as well as other body fluids
• Solid components of body
• Account for 40-50% body mass
• Include organic and inorganic components - proteins, lipids, carbs, minerals
• Minerals - inorganic substances that dissociate in body fluids to form electrolytes
• Fluid balance - because we’re so aqueous in nature
• We are considered in balance when H2O content remains stable over time
• Water gained through - water content of food, beverages consumed, metabolic processes
• Water lost through - urination (50%); losses through feces and evaporation (skin and lungs)
• Water moves b y osmosis - passively flows down osmotic gradients
• Water input, secretion, absorption, and excretion in GI tract
• Fluid balance
• ICF and ECF compartment interactions
• Composition is very different
• At osmotic equilibrium
• Fluid shift - movement of H2O between ECF and ICF in response to osmotic gradients; occurs
rapidly in response to changes in ECF osmotic concentration; equilibrium reached in minutes to
hours; maintains homeostasis of the osmotic concentration between ICF and ECF
• Dehydration
• H2O losses > H2O gains
• H2O moves from ICF —> ECF to reach osmotic equilibrium
• If fluid imbalance continues, loss of H2O from ICF produces severe thirst, dryness, wrinkling of
skin
• Continued fluid loss causes drop in blood volume and BP
• Mineral balance
• Minerals are inorganic; no carbon
• Electrolytes are ions released when mineral salts dissociate
• Mineral balance exists between ion absorption and ion excretion
• Absorption - occurs along lining of SI and colon
• Excretion - kidneys and sweat gland secretion
• Body maintains reserves of key minerals
• Daily intake needs to average amount los
• Body contains substantial reserves of key minerals; common primary routes of excretion - urine;
followed by sweat and feces
• Water and sodium balance
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Document Summary
Distinct environments separated by plasma membranes; maintained by active transport. Icf - cytosolic fluid; most body water found here. Ecf - interstitial fluid and plasma of circulating blood as well as other body fluids. Absorption - occurs along lining of si and colon. If changes are extreme, additional homeostatic mechanisms utilized; ecf volume increases = increases in blood volume and bp; mechanisms respond in order to lower blood volume and pressure. Hyponatremia - low ecf na concentration (<136 meq/l); from overhydration or inadequate salt intake. Hypernatremia - high ecf na concentration (>145 meq/l); dehydration is most common cause: disturbances in potassium balance - predominant cation within the cell; most found within the. Constant production of h+ by these processes creates challenge to acid-base homeostasis: h+ loss, classes of acids that threaten ph balance, metabolic acids - byproducts or participants of cellular metabolism (like lactic acid and ketones);
