Copyright © 2004 Lippincott Williams & Wilkins Chapter 21 Body Fluids

Copyright © 2004 Lippincott Williams & Wilkins The Importance of Water Water is used as a solvent, a transport medium, and participates in metabolic reactions 50-70% of a persons body weight is water Body fluid is maintained in the following ways: Thirst mechanism maintains volume Kidney activity regulates volume and composition Hormones regulate fluid volume and electrolytes Buffers, respiration, and kidney function regulate pH

Copyright © 2004 Lippincott Williams & Wilkins Fluid Compartments Intracellular fluid (ICF) Fluid contained in cells Two-thirds to three-fourths of all body fluids Extracellular fluid (ECF) Interstitial fluid – fluid between the cells n tissues Blood plasma – fluid portion of blood Lymph – fluid drained by the lymphatic system Fluid in special compartments - CSF, synovila capsule, between serous membranes

Copyright © 2004 Lippincott Williams & Wilkins Main fluid compartments showing relative percentage by weight of body fluid. Fluid percentages vary but total about 60% of body weight. Fluids are constantly exchanged among compartments, and each day fluids are lost and replaced.

Copyright © 2004 Lippincott Williams & Wilkins Water Balance Water gain from Beverages Food Cellular respiration Water loss from Kidneys – in urine Skin - Evaporation Lungs – water vapor Intestinal tract within feces Water loss must be replaced or it will disrupt cell processes

Copyright © 2004 Lippincott Williams & Wilkins Sense of Thirst Control center for thirst (Box 21-1) Located in hypothalamus Regulates total fluid volume A decrease in fluid volume or increase in concentration in fluids stimulates thirst Excessive thirst (polydipsia) may be caused by excessive urination as seen with diabetes May not be triggered quickly enough during exercise and/or in the heat which would caused rapid dehydration

Copyright © 2004 Lippincott Williams & Wilkins Electrolytes and Their Functions Conduct electrical current in solution Positive ions (cations) Sodium in the most abundant cation in ECF Required for nerve conduction and maintaining acid- base balance Potassium mostly found in ICF Also needed for nerve conduction as well as in metabolism of carbs and proteins Calcium is stroed predominately in bone Needed for muscle contractions, nerve conduction, and blood clotting Negative ions (anions) Phosphate is essential for carb metabolism, bone formation, and acid-base balance Chloride helps regulate fluid balance and pH and is used for digetsion in the stomach Most abundant anion in the ECF

Copyright © 2004 Lippincott Williams & Wilkins Electrolyte Balance Must be kept in proper concentrations in the ECF and ICF (Read Box 21-2) Kidneys do majority of balancing Hormones involved Aldosterone promotes sodium retention Antidiuretic hormone (ADH) stimulates water retention when sodium concentrations increase Parathyroid hormone increases blood calcuim levels by releasing it from bone Calcitonin hormone lowers calcium levels by depositing it in bone Know what organs secrete these hormones and what happens when out of balance

Copyright © 2004 Lippincott Williams & Wilkins Acid–Base Balance pH scale measures hydrogen ion (H + ) concentration (↑ H + lowers pH, ↓ H + raises pH) Body fluids have normal pH of 7.35 to 7.45 Three-tenths of a point shift in either direction (↓ 7.0 or ↑ 7.7) is fatal Three important Buffer systems accept or release H + as needed to control pH Bicarbonate produced by RBCs and Kidney tubules Phosphate through out the body Proteins mostly within cells

Copyright © 2004 Lippincott Williams & Wilkins Acid–Base Balance Respiration provides short-term regulation Recall that carbonic acid breaks down to CO 2 and H 2 O which allows CO 2 to be expelled at the lungs ↑ CO2 lowers pH, ↓ CO2 raises pH Kidney function provides long-term regulation Reabsorbs or releases hydrogen ions at the kidneys to increase or decrease pH

Copyright © 2004 Lippincott Williams & Wilkins Abnormal pH (Table 21-1) Acidosis pH less than 7.35 Depressed nervous system leading to confusion, coma and ultimately death Results from respiratory obstruction which prevents release of CO2 or kidney failure to eliminate H+ When carbs are unavailable for energy, fat and protein are used which elevate ketone bodies (acids) Condition called Ketoacidosis

Copyright © 2004 Lippincott Williams & Wilkins Abnormal pH (Table 21-1) Alkalosis –pH greater than 7.45 –Excites the nervous system to produce a tingling sensation, muscle twitches, or even paralysis –Caused by Decreased CO2 from hyperventilation Ingestion of too much antacid Prolonged vomiting and loss of stomach acids

Copyright © 2004 Lippincott Williams & Wilkins Disorders of Body Fluids Edema Accumulation of excess fluids in interstitial space (between cells) Caused by Decreased fluid return to the heart, as in congestive heart failure, leads to a backup of fluid in the lungs (pulmonary edema) Protein deficiency decreases plasma proteins reducing blood osmotic pressure and fluid accumulates in tissues Kidney failure cannot eliminate water through the production of urine

Copyright © 2004 Lippincott Williams & Wilkins

Disorders of Body Fluids Water Intoxification Disrupts Nervous activity and may lead to coma dilutes both ICF and ECF Caused by too much ADH production or excessive water intake by mouth or IV Dehydration Reduction of body fluids which increases electrolyte concentration of fluids Caused by vomiting, diarhea, burn wounds, excessive perspiration, or inadequate intake. Results in nervous and cardiac breakdown Fluids need to be administered by mouth or IV ASAP

Copyright © 2004 Lippincott Williams & Wilkins Fluid Therapy Fluids administered intravenously (Read Box 21-3) Normal (.9%) saline (isotonic) 5% dextrose in.45% saline (hypertonic, but becomes hypotonic after glucose is metabolized)) 5% dextrose in water (hypotonic) Ringer lactate solution increased plasma volume levels with the addition of buffers Serum albumin 25% (5X normal) draws fluids from interstitial spaces into blood Nutritional solutions of glucose, protein, and lipids given when oral intake is not possible for extended periods.