Body Fluid Compartments - SI2101 Lecture Notes PDF

SI2101 - LECTURE 4 Body uid compartments and constituents Leo Quinlan, Cell Physiology Research Lab fl  Describe the distribution of water in the body and know the volumes Know the concentrations of the major cations and anions in different body uid compartments Know how...

SI2101 - LECTURE 4 Body uid compartments and constituents Leo Quinlan, Cell Physiology Research Lab fl  Describe the distribution of water in the body and know the volumes Know the concentrations of the major cations and anions in different body uid compartments Know how concentrations are expressed in biological uids and why LEARNING OUTCOMES FOR TODAY fl fl  THINGS TO THINK ABOUT OVER THE NEXT 4 LECTURES How are body uids distributed among different compartments, and what roles do these compartments play in maintaining homeostasis? Why is it important for the body to regulate the balance of electrolytes within these compartments? How do conditions such as dehydration or overhydration affect electrolyte balance and uid distribution? How do transport processes contribute to maintaining uid and electrolyte balance? How can understanding body uid compartments and electrolytes help in diagnosing and treating medical conditions such as heart failure, kidney disease, or electrolyte disorders? What body systems help control uid and electrolyte balance How do diet, exercise, and lifestyle choices impact the balance of body uids and electrolytes? Do I need to worry about management of uid and electrolyte? fl fl fl fl fl fl BODYBAG FLUID COMPARTMENTS FLUID COMPARTMENTS  Most of body bulk = water. Approx 60% Constituents determine the nature of nearly every physiological process. 55-60% of total body weight is uid. BULK BODY FLUIDS fl  Body uid compartmentalised Intracellular Fluid (ICF) comprises 2/3 of the body's water. Extracellular Fluid (ECF) comprises 1/3 of the body's water BULK BODY FLUIDS fl  ICF approx. 40% of body weight. Solution of K+, anions, proteins etc. (Cellular Soup!). Cell membrane & cellular metabolism controls constituents of ICF. ICF is not homogeneous throughout body. It represents a conglomeration of uids from all the different cells. INTRACELLULAR FLUID (ICF) fl  ECF approx 20% of your weight. Primarily a Na+ and HCO3- (bicarbonate) solution. Subdivided into 3 sub-compartments: Interstitial Fluid (ISF) Plasma Transcellular uid EXTRACELLULAR FLUID (ECF) fl FLUID COMPARTMENTS FLUID COMPARTMENTS  Understanding Homeostasis SO WHAT ? Regulation of body uid compartments and their volumes are crucial for homeostasis, the stable internal environment necessary for optimal cellular function. Knowledge of uid compartments is essential for studying physiological processes such as nutrient transport, waste removal, and cellular communication. Medical Applications: Many medical conditions, such as dehydration, edema, and electrolyte imbalances, are directly related to uid compartment volumes. Understanding how drugs distribute across different uid compartments is vital for pharmacokinetics and pharmacodynamics. Fluid compartment analysis is used in diagnostic tests to assess kidney function, blood pressure regulation, and other conditions Many diseases, such as heart failure, liver cirrhosis, and kidney disease, affect uid balance and distribution. Research on Aging / Development and elite performance: Changes in body uid compartments occur with aging and development. Factors like diet, exercise, climate, and altitude affect uid balance and health. fl fl fl fl fl fl  All compartments are in osmotic equilibrium (except for transient changes). Ions and small solutes that constitute the ECF are in equilibrium with similar concentrations in each sub- compartment. The ECF volume is proportional to the total Na+ content. THINGS TO NOTE ABOUT BODY FLUIDS  Intracellular and extracellular uids contain Electrolytes A substance that dissociates into ions in solution Common electrolytes include Na+, K+, Ca2+, Mg2+, Cl , HCO3 , PO4 Na+, K+, Ca2+ play roles in muscle contraction, the transmission of nerve impulses and in secretion/absorption Cl is involved in acid base balance and muscular activity, HCO3 , PO4 play essential roles in physiological buffers IONIC COMPOSITION ‐ ‐ ‐ ‐ fl ‐ WHAT ELECTROLYTES ARE FOUND WHERE ? UNITS OF MEASURE IN SOLUTIONS A Molar Solution is an aqueous solution consisting of one mole of a substance plus enough water to make 1 L of solution. EVEN DISTRIBUTION IN PURE WATER A Molal Solution is an aqueous solution consisting of one mole of a ~7% NON AQUEOUS substance in 1 kg of water. Difference is NB E.g. cream has 20% fat thus there is a 20% difference molarity Vs molality. PLASMA IS NOT PURE WATER WHAT ELECTROLYTES ARE FOUND WHERE ? UNITS OF MEASURE IN SOLUTIONS Equivalents (milliequivalents, mEq) per Liter. Equal to the molarity X the charge number. Measure of CHARGE concentration. 150mMolar Na+ = 150mEq / L 50mMolar Ca2+ = 100mEq / L (50 X charge no. I.e. 2) WHAT ELECTROLYTES ARE FOUND WHERE ? WHAT DO I NEED TO REMEMBER ?  Describe the distribution of water in the body and know the volumes Know the concentrations of the major cations and anions in different body uid compartments Know how concentrations are expressed in biological uids and why LEARNING OUTCOMES FOR TODAY fl fl