Body Fluids and Regulation of Fluid Balance Lecture PDF

Body Fluids, and Regulation of Fluid balance 1st year Faculty of Applied Health Sciences & Technology By Dr. Rasha Mohammed Ali Lecturer of Medical Physiology, Faculty of Medicine, Assiut University...

Body Fluids, and Regulation of Fluid balance 1st year Faculty of Applied Health Sciences & Technology By Dr. Rasha Mohammed Ali Lecturer of Medical Physiology, Faculty of Medicine, Assiut University Foundation 2024-2025  Objectives: 1. To Identify the body’s main body fluid compartments 2. Explain the principles of measurements of body fluid compartments 3. Describe the functions of water 4. To describe the regulation of fluid and electrolyte balance. 5. To describe types of Intravenoud fluid therapy PERCENTAGE OF H2O IN TISSUES  Body fluid compartments Average 70 kg person total body weight 42 litres total H2O 60% A. 28 l. Intracellular fluid (ICF) 40% TISSUE B. 14 % WATER % BODY Wt. L of H2fluid l. Extracellular O (ECF) 20% Skin 72 18 9.1 Muscle 1. ECF 76 is important 41.7 22.1 in fluid therapy Skeleton 22 16 2.5 2. ECF is divided into ¾ ISF and ¼ plasma water Brain 74.8 2.0 1.0 Liver 10.5 68.3 l. Interstitial 2.3 1.0fluid (ISF): 15% Blood 83.0 8.0 4.65 Intestine 3.574.5 l. Plasma 1.8 1.0 5% water: Adipose Tissue 10.0 10+ 0.7  FLUID COMPARTMENTS EXTRA CELLUAR INTRA CELLULAR FLUID (cytosol)FLUID PLASMA INTERSTITIAL TRANSCELLULAR FLUID FLUID CSF, Intra ocular Pleural Peritoneal Synovial Digestive Secretions Measurement of volumes of Body Fluid Compartments  Measurement of volumes of Body Fluid Compartments Principle of measurement:  A known amount of a dye or indicator is injected into the body.  Then the dye concentration in that compartment is measured.  The compartment volume is calculated as follow:  5 gm Concentration 10 mg/ml Volume = 5000/10 = 500 ml  CRITERIA FOR A SUITABEL DYE.  BODY FLUID MARKER 1. Must mix evenly throughout the compartment 2. Nontoxic, no physiological activity 3. Must have no effect of its own on the distribution of H2O 4. Not metabolized, not excreted 5. Either it must be unchanged during the experiment or if it changes , the amount changed must be known. 6. The material should be relatively easy to measure.  Measurement of Total Body Water Measurement of total body water:  Can be measured by Deutrium oxide (D2O, heavy water), Tritium oxide and Aminopyrine  They are distributed ICF and ECF Problem:  Amount of D2O injected = 4 mg  Plasma concentration = 0.01 mg/dl. 4 mg Volume = = 40 Liters 0.01 x 10  Measurement of ECF and ICF Volumes Measurement of ECF volume:  Can be measured by Inulin (more accurate), Mannitol and Sucrose  They are distributed ECF only Measurement of ICF volume :  Not directly measured  But measured by the following formula; ICF = Total body water – ECF  Measurement of Plasma Volume Measurement of plasma volume:  Can be measured by Evans blue dye (more common) or radioactive iodine bound to plasma proteins  They are distributed only in vascular part of ECF Measurement of ISF :  Cannot be measured directly but measured by  ISF= ECF – plasma volume  Indicators used for measuring plasma volume, ECF volume and total body H2O Compartment Criterion Indicators 1. Plasma Substance 1. Evans blue dye; should not cross 2. radioiodinated fibrinogen; capillaries 3. radioiodinated albumin 1. ECF Substance Isotonic solutions of sucrose, volume should cross inulin, mannitol, NaCl capillaries but not cross cell membranes 1. Total Substance Heavy H2O, tritiated H2O, body H2O distributes aminopyrine, antipyrine (TBW) evenly in ICF & ECF Functions of Body Water  Water Balance Definition:  Body water is kept constant by adjusting water input and water output Water output 2400 ml/day Water Input Insensible water 2400 ml/day loss (about 700ml)(100 Sweating Endogenous water ml) 200 ml/day Feces (about 100ml) Exogenous water Urine (about 1500 2200 ml/day ml)  Control of Water Input ↓ blood volume Thirst Center (Hypovolaemia ) Angiotensin ↑ Thirst II ↑ sensation ↑ plasma osmolarity (Hypertonicity) Increased water intake ↓ plasma osmolarity blood volume  Control of Water Output ↓ blood volume (Hypovolaemia Posterior ) pituitary ADH Angiotensin secretion II blood volume ↑ plasma osmolarity (Hypertonicity) ↓ plasma osmolarity blood volume ↓ Urine volume  Electrolytes Cation - positively charged electrolyte, e.g.Na+, k+,Ca+2 Anion - negatively charged electrolyte, e.g, Cl- , HCO3- po4-3 ✓ The chief extracellular cation is Na+ ✓ The chief intracellular cation is k+ ✓ Cl- is the predominant anion outside cells ✓ whereas phosphates constitute the bulk of intracellular anions..