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DR. ZAHOOR ALI SHAIKH Lecture--5. BODY FLUIDS AND ELECTOLYTES. HUMAN BODY COMPOSITION. Human Body Composition: Water ---- 60% Protein --- 18% Fat -------- 15% Mineral --- 07 %. BODY WATER. Body water makes 60% of body weight.
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DR. ZAHOOR ALI SHAIKH Lecture--5 BODY FLUIDS AND ELECTOLYTES
HUMAN BODY COMPOSITION • Human Body Composition: • Water ---- 60% • Protein --- 18% • Fat -------- 15% • Mineral --- 07 %
BODY WATER • Body water makes 60% of body weight. • Therefore body water is about 42 liters in 70 kg person. • Body water is distributed between TWO major compartments: 1. INTRACELLULAR FLUID (ICF) 2. EXTRACELLULAR FLUID (ECF)
BODY WATER DISTRIBUTION • We will see how this 42 liters of water is distributed between ICF and ECF • Total Body Water (TBW)--- 42 liters - Intracellular fluid (ICF)----- 28 liters - Extracellular fluid(ECF)-----14 liters ( ECF IS DIVIDED INTO INTERSTITIAL FLUID AND PLASMA ).
EXTRA CELLULAR FLUID • Extracellular fluid (ECF)- 14 lit is divided into: - Interstitial fluid --- 11 liters - Plasma -------------- 3 liters • Note-- Interstitial fluid is the fluid which is distributed between the cells or surrounding the cells. Plasma – It is fluid portion of blood.
TOTAL BODY WATER • SUMMARY • TOTAL BODY WATER (TBW) – 42 liters - Intracellular fluid – 28 liters - Extracellular fluid – 14 liters (i). Interstitial fluid – 11 liters (ii). Plasma - 3 liters
OTHER EXTRACELLULAR COMPARTMENT • There are other TWO Minor Extracellular fluid compartments also: 1. Lymph 2. Transcellular fluid 1. Lymph It is fluid which is returned from the interstitial fluid to plasma by means of Lymphatic System.
Minor ECF Compartment (cont) 2. Transcellular Fluid • It is small fluid volume secreted by specific cells in the body, these cells perform special function • Example of Transcellular fluid - Cerebrospinal fluid (CSF)- it surrounds the Brain and Spinal cord - Intra ocular fluid - in the eye - Synovial fluid – lubricating joints - Pericardial fluid, Intra pleural fluid
Extracellular Fluid[Plasma & Interstitial Fluid] • Plasma and Interstitial Fluid are separated by blood vessel wall. • Water and electrolyte are freely exchanged between plasma and interstitial fluid passively through pores of thin capillary membrane.
Extracellular Fluid[Plasma & Interstitial Fluid] (cont) • But Plasma protein can not pass from plasma to interstitial fluid. • Therefore plasma and interstitial fluid are nearly same in composition except that plasma has protein and interstitial fluid doesn’t have protein.
Extracellular Fluid [ECF] & Intracellular Fluid [ICF] • ECF and ICF are separated by plasma membrane. • Plasma membrane is selectively permeable. • There is passive transport and active transport occurring through the plasma membrane. • There is difference between ECF and ICF.
Extracellular Fluid [ECF] & Intracellular Fluid [ICF] Major Ionic Composition
Na+ and K+ Concentration In ECF & ICF Q. Why Na+ is more in ECF and K+ more in ICF? Ans: It is due to the Na+ - K+ ATPase pump which pumps Na+ outside the cell and K+ inside the cell.
‘Important Things To Remember’ • Both Interstitial Fluid and Plasma have same composition except that Plasma has more protein. • ICF and ECF are different as plasma membrane is selectively permeable and Na+ - K+ ATPase pump is operating.
‘Important Things To Remember’ • ECF Na+ 140 mmol / l (135-145 mmol / l) K+ 4 mmol / l (3.5 – 5 mmol / l) Cl- 105 mmol / l (100 – 110 mmol / l)
Fluid Balance • Fluid Balance is regulated by: 1- ECF Volume 2- ECF Osmolarity - ECF volume helps to maintain blood pressure and will be discussed later with blood pressure. We will discuss ECF Osmolarity.
ECF OSMOLARITY • What is Osmolarity ? • Osmolarity is the concentration of solute particles dissolved in the fluid. • Increased Osmolarity means higher concentration of solute and less concentration of water.
ECF Osmolarity (cont) • As Na+ is the main solute in ECF, it is responsible for ECF Osmolarity. • In ICF K+ is responsible for ICF Osmolarity. • Normally ECF and ICF are ISOTONIC (having same Osmolarity).
Extracellular Fluid Osmolarity • Normally Osmolarity of ECF and ICF are the same (they are isotonic). • Why ? • Because total concentration of Na+ and other solutes in ECF is equal to total concentration of K+ and other solutes inside the cell. • Remember Osmolarity of ECF - 285 mmol/l (275 – 295)
Importance of regulating ECF Osmolarity • PROBLEM • If there is water loss from the ECF , what will be its effect ? Answer – ECF will become Hypertonic.
Hypertonic Extracellular Fluid • ECF will become hypertonic if water is lost from it e.g. diarrhea, vomiting, sweating or less water intake. • If ECF becomes more hypertonic, water moves from the cells into ECF by osmosis (i.e. from ICF to ECF). • As water leaves the cell – cell will shrink.
Clinical Application • In mild Dehydration (loss of water) and mild hyper tonicity --- There is dry skin, dry tongue thirst, sunken eyes. • In case of severe Hyper tonicity ( Hyper Osmolarity) of ECF, it may affect BRAIN CELLS and BRAIN FUNCTION --- person may become mentally confused.
HYPOTONIC ECF • PROBLEM • What will happen if ECF becomes Hypotonic (that is having less Osmolarity) ? • Answer – When ECF becomes Hypotonic , water will enter the cell, and cell will swell ( get bigger). • NOTE – Usually Hypo tonicity does not occur because when we take more water, we loose water in urine, but it can happen in Abnormal conditions.
Hypotonic Extracellular Fluid(cont) Clinical Application • In Renal failure, patient can not pass urine , therefore ECF will become hypotonic if water is added to it. • When ECF becomes hypotonic, water will enter into the cell by Osmosis and cells will swell (increase in size). • Swelling of BRAIN cells will cause Brain Dysfunction E.g. – headache, vomiting, confusion, drowsiness and coma. This is called WATER INTOXICATION.
ISOTONIC SOLUTIONS • What will happen if we give Is0tonic solution? • Answer – If we give ISOTONIC SOLUTION like o.9% saline (Isotonic saline) intravenously, ECF will remain ISOTONIC , there will be no net movement of water into or out of the cells. Only ECF volume will increase. • NOTE – In case of Diarrhea, vomiting , Isotonic saline is given intravenously .
What Should You Know From This Lecture • Distribution of Body water – ICF, ECF [Interstitial Fluid in Plasma] • Define Tran cellular Fluid • Compare Ionic composition of Plasma, Interstitial Fluid and Intracellular Fluid • What is Osmolarity of Plasma? • Define Isotonic, Hypotonic, Hypertonic • What are causes of ECF hyper tonicity and hypo tonicity and its effects on body?