Homeostasis A Water balance and body fluid compartments
Homeostasis A Water balance and body fluid compartments Year 2 Unit I 10/31/2021 1
Learning objectives • Sources of Body Water Gain and Loss • Indicate the relative fluid volume and solute composition of the fluid compartments of the body. • Calculate the fluid volume of body fluids compartments • List the factors that determine body water content including age, body mass, and body fat. • List and know the main the mechanisms which maintains fluids and electrolyte balance and control of plasma osmolality • Define and calculate plasma osmolality • Explain the mechanism of water moment between fluid compartments • Understand the concept of osmotic equilibrium and be able to calculate plasma osmolarity and body fluid volume following the infusion of iv fluids (for example saline) 9/23/2017 2
Water Balance Water gain 2. 2 L/day Water loss Food and drink Skin Insensible water loss 0. 9 L/day Lungs 0. 3 L/day 2. 5 L/day Metabolism Totals Intake Metabolic production + – 2. 2 L/day 0. 3 L/day 10/31/2021 Urine 1. 5 L/day Feces 0. 1 L/day 2. 5 L/day Output 2. 5 L/day =0 4
Balance Concept Fluid and electrolyte balances are necessary, in the long-term, to maintain life. Fluid Loss = Fluid Intake Electrolyte Loss = Electrolyte Intake Fluid Intake: regulated by thirst mechanism, habits Electrolyte intake: governed by dietary habits Fluid Output: regulated mainly by kidneys Electrolyte output: regulated mainly by kidneys 10/31/2021 4
Fluid intake. Fluid and out put after the ingestion of adult high Balance (ml/day) – 70 kg salt diet Normal High Salt Diet Intake (ml/day) Fluids ingested From metabolism Output (ml/day) Insensible - skin Insensible – lungs Sweat Feces Urine 10/31/2021 2100 2300 4100 200 4300 350 100 1400 2300 350 100 3400 4300 5
Fluid (ml/day) – 70 kg adult Fluid intake and. Balance out put after heavy exercise Normal Heavy Exercise Intake (ml/day) Fluids ingested From metabolism Output (ml/day) Insensible - skin Insensible - lungs Sweat Feces Urine 10/31/2021 2100 2300 350 100 1400 2300 6400 200 6600 350 650 5000 100 500 6600 6
Distribution and calculation of body fluids compartments 1. TBW is 60%of body weight 2. 40% of body wieght is ICF 3. 20 of body weight % is ECF 2. 2/3 of TBW is ICF 3. 1/3 is of TBW is ECF 70 kg adult male 10/31/2021
ECF compartments • Interstitial fluid compartment : bathing the cells and constitute about 75 % of ECF (11 L) • Plasma and lymph (intravascular fluid compartment) approximately 25 % of ECF 3 L • Transcellular fluid compartment Small amount of interstitial found in special compartments including CSF, plural fluid , synovial fluid, pericardial fluid (1) 10/31/2021 8
Major cations and anions of Intra cellular and extracellular fluids 31/10/2021
Non electrolytes of the plasma 31/10/2021
The fluid compartments and electrolyte composition of an adult human weighing 70 kg. 31/10/2021
Total Body Water in Relation to Body Weight: Effects of Gender, Body Build and Age Body Build TBW (%) Adult Male TBW (%) Adult Female TBW (%) Infant Normal 60 50 70 Lean 70 60 80 Obese < 50 <42 <60 Increasing obesity decreases TBW % Increasing age decreases TBW % 10/31/2021 12
Measuring Body Fluid Volumes: Indicator Dilution Principle Indicator Mass A = Volume A x Concentration A A Indicator Mass A = Indicator Mass B Volume B = Indicator Mass B / Concentration B Indicator Mass B = Volume B x Concentration B 10/31/2021 13
Indicator Dilution Principle Volume (B) = Indicator Mass (B) = Q (amt. injected) Concentration (B) C (after equilibrium) Valid if: • Indicator disperses only in compartment measured • Indicator disperses evenly in compartment • Indicator not metabolized or excreted (or correction must be made for excretion/metabolism) 10/31/2021 14
Distribution and calculation of body fluids compartments 1. TBW is 60%of body weight 2. 40% of body wieght is ICF 3. 20 of body weight % is ECF 2. 2/3 of TBW is ICF 3. 1/3 is of TBW is ECF 70 kg adult male 10/31/2021
TPRBlem ake Question. Take You want to measure total body water in a patient. You inject 10 ml of a solution of antipyrine with a concentration of 150 mg/ml i. v. After equilibrium, the concentration of antipyrine in the blood is 0. 03 mg/ml. What is the total body water of this patient, assuming no excretion ? Amount antipyrine injected (Q) = 10 ml x 150 mg/ml = 1500 mg Total body water volume = 10/31/2021 Q / C (after equilibrium) = 1500 mg / (. 03 mg/ml) = 50, 000 ml = 50 liters 16
Calculations of various fluid volumes 31/10/2021
Fluid and Electrolyte Homeostasis Blood volume Blood pressure Volume receptors in atria and carotid and aortic baroreceptors trigger homeostatic reflexes Cardiovascular system Behavior Cardiac output, vasoconstriction Kidneys Thirst causes water intake ECF and ICF volume KEY Stimulus Receptor Blood pressure (a) 31/10/2021 Conserve H 2 O to minimize further volume loss Effector Tissue response Systemic response
Response to water deprivation 31/10/2021
Endocrine and neuronal regulation of fluid and electrolytes balance Osmoreceptor– antidiuretic hormone (ADH) feedback mechanism for regulating extracellular fluid osmolarity. 10/31/2021 Figure 28 -9 21
Control of water balance : ADH synthesis in the magnocellular neurons of hypothalamus, release by the posterior pituitary, and action on the kidneys 10/31/2021 22
Renin Angiotensin Aldosterone system and fluids and electrolytes balance 10/31/2021 23
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