Body Fluids Compartments and Ionic Composition PDF

# Body Fluids Compartments and Their Ionic Composition ## Introduction ### Human Physiology - It is the science that deals with the functions of the human body. - It explains the characteristics and mechanisms of the human body that makes it a living being. - The fact that we remain alive is the...

# Body Fluids Compartments and Their Ionic Composition ## Introduction ### Human Physiology - It is the science that deals with the functions of the human body. - It explains the characteristics and mechanisms of the human body that makes it a living being. - The fact that we remain alive is the result of complex control systems. - Hunger makes us seek food, and fear makes us seek refuge. Sensations of cold make us look for warmth. - These special attributes allow us to exist under widely varying conditions that otherwise would make life impossible. - Human physiology links the basic sciences with medicine and integrates multiple functions of the cells, tissues, and organs into the functions of the living human being. ### The major levels of organization - The basic living unit of the body is the cell. - The major levels of organization in the body are: 1. **Chemical Level:** Various atoms (e.g., oxygen, carbon, hydrogen, and nitrogen) and molecules (e.g., proteins, carbohydrates, fats, and nucleic acids) make up the body. 2. **Cellular levels** All cells in our body have basic functions e.g., - Obtaining food (nutrients) and $O_2$ from the environment surrounding the cell. - Performing chemical reactions that use nutrients and $O_2$ to provide energy for the cells, as follows: Food + $O_2$ → $CO_2$ + $H_2O$ + energy. - Eliminating $CO_2$ and other wastes to the cell's surrounding environment, produced during these chemical reactions. - Each cell performs one or a few specific functions e.g., red blood cells transport oxygen from lung to tissues, beta cells of pancreas release insulin hormone…etc. - **Tissues:** Tissues are groups of cells of similar specialization, e.g., Muscle tissue consists of cells specialized for contracting, which generates tension and produces movement. - **Organs:** An organ is a unit made up of several tissue types, e.g. Stomach. - **Systems:** The body system level: A body system is a collection of related organs. Each system is a collection of organs that perform related functions and interact to accomplish a common activity essential for survival of the whole body, e.g., digestive system, respiratory system. - **Human organism:** The body systems are packaged into a functional whole body. ## Intended Learning Outcomes 1. Recall the distribution of total body water 2. Recognize the different fluid compartments in the human body. 3. Distinguish between extracellular fluid and intracellular fluid 4. Measure the different body fluid volume 5. Assess the changes in volume and osmolarity in body fluid compartments in many physiological conditions ## Body Fluids - 60% of the adult human body is fluid, mainly, a water solution of ions and other substances. - Total body fluid (total body water, TBW) is 42 liters in 70 Kg adult male. - **Physiological factors affecting the TBW:** 1. **Body fat content:** Fat tissues have low water content. Therefore, obese people have low TBW. 2. **Sex:** Females have lower TBW than males because females normally have greater body fat compared to males. 3. **Age:** Young people have greater TBW than old people. | Physiological Level of TBW | TBW (% of body weight) | | - | - | | Fetus | 97% | | Infant | 75% | | Male | 60% | | Female | 50% | *Fetus is an unborn human baby, third month after fertilization until birth. An infant is live born and younger than one year of age.* ## Distribution of TBW in a healthy adult 70 Kg male - An image depicting a 70 kg male with a table summarizing the various percentages of body weight attributed to different compartments: - Total body mass (male): 70 kg - Solids: 40% body weight - Water: 60% body weight - Intracellular fluid: 2/3 TBW, 40% body weight, 28L - Extracellular fluid: - Intra-vascular fluid: 1/3 TBW, 20% body weight, 14L - Plasma: 5% body weight, 3.5L - Interstitial fluid: 15% body weight, 10.5L ## Human Circulatory System - An image depicting the human circulatory system, including the pulmonary and systemic circuits. - An image depicting a zoomed-in view of a capillary bed, including the blood flow and filtration and absorption processes. - _Internal Jugular Vein_ - _External Jugular Vein_ - _Subclavian Vein_ - _Pulmonary Artery_ - _Superior Vena Cava_ - _Cephalic Vein_ - _Inferior Vena Cava_ - _Hepatic Vein_ - _Renal Vein_ - _Hepatic Portal Vein_ - _Basilic Vein_ - _Median Cubital Vein_ - _Common Iliac Vein_ - _Palor Digital Veins_ - _Great Saphenous Vein_ - _Femoral Vein_ - _Small Saphenous Vein_ - _Anterior Tibial Vein_ - _Posterior Tibial Vein_ - _Dorsal Venous Arch_ - _Dorsal Digital Vein_ - _Internal Carotid Artery_ - _External Carotid Artery_ - _Common Carotid Artery_ - _Subclavian Artery_ - _Pulmonary Veins_ - _Axillary Artery_ - _Axillary Vein_ - _Heart_ - _Pulmonary Arteries_ - _Aorta_ - _Descending Aorta_ - _Gastric Artery_ - _Brachial Artery_ - _Renal Artery_ - _Mesenteric Artery_ - _Common Iliac Artery_ - _Ulnar Artery_ - _Radial Artery_ - _Arterial Palmar Arch_ - _Digital Arteries_ - _Femoral Artery_ - _Anterior Tibial Artery_ - _Posterior Tibial Artery_ - _Peroneal Artery_ - _Arcuate Artery_ - _Dorsal Digital Arteries_ ## Transcellular Fluid ### Transcellular Fluids as a Minor ECF Compartment - __Transcellular Fluid__ consists of a number of small, specialized fluid volumes in a particular body cavity to perform some specialized function. - **Transcellular fluid includes:** 1. Cerebrospinal fluid 2. Intraocular fluid 3. Synovial fluid 4. Pericardial, intrapleural, and peritoneal fluids 5. Digestive juices - These fluids represent an insignificant fraction of TBW. Localized fluid disturbance in transcellular fluid does not affect the fluid balance of the body, except digestive juices which when lost during vomiting or diarrhea they lead to fluid imbalance. ## Exchange Between Compartments - There is a continuous exchange among various body fluid compartments which maintains dynamic equilibrium. - This exchange exists between: 1. ICF and ISF through plasma membrane. 2. Plasma and ISF through the capillary walls. ## Ionic Composition of Different Compartments ### Difference Between ISF and Plasma - Plasma and ISF are similar in composition EXCEPT that ISF lacks plasma proteins. - Because the plasma and interstitial fluid are separated only by highly permeable capillary membranes (thin and pore-lined), their ionic composition is similar. - The most important difference between these two compartments is the higher concentration of protein in the plasma because the capillaries have a low permeability to the plasma proteins, only small amounts of proteins are leaked into the interstitial spaces in most tissues. *N.B. Any change in one of these ECF compartments is quickly reflected in the other compartment because they are constantly mixing.* ### Difference Between ECF and ICF - Each cell is surrounded by a highly selective plasma membrane that permits passage of certain materials while excluding others. - Movement through the membrane barrier is highly discriminating. ## Main Differences between ECF and ICF compositions | | ECF | ICF | | - | - | - | | $Na^+$ | 142 mEq/L | 10 mEq/L | | $K^+$ | 4 mEq/L | 140 mEq/L | | $Ca^{2+}$ | 2.4 mEq/L | 0.0001 mEq/L | | $Mg^{2+}$ | 1.2 mEq/L | 58 mEq/L | | $Cl^-$ | 103 mEq/L | 4 mEq/L | | $HCO_3^-$ | 24 mEq/L | 10 mEq/L | | Phosphates | 4 mEq/L | 75 mEq/L | | $SO_4^{2-}$ | 1 mEq/L | 2 mEq/L | | Glucose | 90 mg/dl | 0 to 20 mg/dl | | Amino acids | 30 mg/dl | 200 mg/dl? | | Cholesterol | 0.5 g/dl | 2 to 95 g/dl | | Phospholipids | - | - | | Neutral fat | - | - | | $PO_2$ | 35 mm Hg | 20 mm Hg? | | $PCO_2$ | 46 mm Hg | 50 mm Hg? | | pH | 7.4 | 7.0 | | Proteins | 2 g/dl (5 mEq/L) | 16 g/dl (40 mEq/L) | ### Cations and Anions | | ICF | ECF | | ------ | ------ | ------ | | Cations | $K^+$ | $Na^+$ | | Anions | Phosphates and proteins | $Cl^-$ and $HCO_3^-$ | ### Proteins - ICF contains a higher concentration of protein than ECF, as proteins cannot cross the cell membrane and are trapped inside the cell. - Plasma contains a higher concentration of proteins (plasma proteins) than ISF because of low permeability of capillary wall to plasma proteins (large molecular weight of plasma proteins which reduce their passage through the capillary wall). Normally, a small amount of proteins are leaked into the ISF. ## Student Activity *True and false* - Capillary wall is a barrier between ISF and plasma. **True** - Main ICF cation is $Na^+$. **False** - The highest concentration of proteins are found in ICF. **True** ## Movement of Water Between Different Compartments ### Hydrostatic Pressure - Hydrostatic pressure is the pressure exerted by the fluid present in a closed compartment. It pushes the fluid outside this compartment. In our bodies, blood inside the capillaries has a hydrostatic pressure which tends to push fluid into the interstitial space. ### Osmosis - Water moves between different body compartments by osmosis from compartment with low solute concentration to compartment with high solute concentration. - Presence of solute trapped inside compartments creates an osmotic pressure which withdraws fluid into the compartment. ### Clinical Note - Edema - Edema is excess ISF and accumulation of fluid extracellularly. - **Causes:** 1. Increased capillary hydrostatic pressure (as in case of right-side heart failure), results in increased ISF formation. 2. Decreased plasma osmotic pressure (hypoproteinemia which is low levels of plasma proteins). - Edema is often observed in the feet, ankles, and legs, but can happen in many areas of the body in response to disease. ## ECF as an Internal Environment - ECF is in constant motion throughout the body. - It is transported in the circulating blood and mixed between the blood and tissue fluids through the capillary walls. - ECF contains the ions and nutrients required by the cells to maintain life. - Also, it is the site at which waste products of the cells are eliminated. Therefore, all cells live in essentially the same environment (ECF). - Thus, the ECF is called the internal environment of the body. ## Measurement of Body Fluid Compartment Volumes: Indicator-Dilution Principle - The volume of a fluid compartment in the body can be measured by placing an indicator substance in the compartment, allowing it to disperse evenly throughout the compartment's fluid, and then analyzing the extent to which the substance becomes diluted. This is called the **indicator-dilution method**. - Total mass of a substance after dispersion in the fluid compartment = Total mass injected into the compartment. - **Steps** 1. A small amount of dye or other substance contained in is injected into a chamber 2. The substance is allowed to disperse evenly in the chamber fluid. 3. Then a sample of fluid containing the dispersed substance is removed, and the concentration is analyzed chemically, photoelectrically, or by other means. 4. If none of the substance leaks out of the compartment, the total mass of substance in the compartment can be calculated as follows: - Volume (ml) = total amount of substance injected / concentration of substance in the dispersed fluid - **Properties of the used substance:** 1. The indicator disperses evenly throughout the measured compartment. 2. The indicator disperses only in the compartment that is being measured. 3. The indicator is not metabolized or excreted. If the indicator is metabolized or excreted, correction must be made for loss of the indicator from the body. 4. The indicator must not affect the distribution of body water. 5. The indicator must be inert, non-toxic, easily measurable, and not changed during the dispersing period. ## Indicators Used for Measurement of Different Body Fluid Compartment Volumes - Indicator-Dilution Principle | Compartment | Characteristics of Indicator | Indicator | | - | - | - | | TBW | Should be distributed in all body compartments (plasma, ISF, and ICF):<br> - Can cross capillary wall.<br> - Can cross the cell membrane. | 1. Deuterium oxide ($^2H_2O$)<br> 2. Tritium oxide ($^3H_2O$)<br> 3. Antipyrine | | ECF | Should be distributed in ECF only (plasma and ISF): <br> - Can cross capillary wall.<br> - Can not cross the cell membrane. | 1. Inulin<br> 2. Thiosulfate , Thiocyanate<br> 3. Sucrose<br> 4. Mannitol<br> 5. Radioactive isotope of sodium, and bromide | | Plasma | Should be distributed in plasma only: <br> - Can not cross capillary wall.<br> - Can not cross the cell membrane. | 1. Evan's blue<br> 2. Radioactive albumin (albumin labelled with radioactive iodine) | | Blood volume | - | 1. $^{51}Cr$-RBCs | *N.B. ICF and ISF can not be directly measured; but they are calculated.* ## Calculation of ISF and ICF - ECF= Plasma + ISF <br> - ISF=ECF-Plasma <br> - TBW=ICF+ECF <br> - ICF=TBW-ECF ## Measurement of Blood Volume - Total blood volume represents 8% of body weight. - Blood is composed of plasma (fluid part; 55%) and cells (RBCs, WBCs, and platelets, 45%). - The percentage of RBCs to total blood volume is called hematocrit value (45% or 0.45). - Blood volume can be calculated by : 1. Determining the hematocrit and plasma volume (measured by indicator dilution principle using Evans blue or radioactive albumin). Blood volume can be calculated as follows: - Blood volume = plasma volume / (1- hematocrit) 2. Determination of RBCs volume: - Injecting RBCs that have been labeled with radioactive material (chromium, 51Cr) into the circulation. - After these mix in the circulation, the radioactivity of a mixed blood sample can be measured, and the total blood volume can be calculated using the indicator-dilution principle. - Blood volume = RBCs volume x 100 / hematocrit ## Water Balance | Water Balance | In Normal Activity and Moderate Atmospheric Temperature | | - | - | | Sources of Water Gain | Sources of Water Loss | | 1. Food and drinking (2.2 L/day) <br> 2. Body oxidative metabolism (0.3 L/day) <br> **In Disease:** - Intravenous fluid infusion | 1. Urine (1.5 L/day)<br> 2. Insensible water loss through the respiratory tract and skin (0.9L/day) <br> 3. Stool (0.1 L/day) <br> **In Disease:** - Diarrhea and vomiting | - Water gain > water loss = **Overhydration or water overload** - Water loss > water gain = **Dehydration** ## Student Activity *True and false* - Indicator used to measure ECF must cross cell membrane. **False** - ECF is the internal environment of the body. **True** - Evan's blue is used to determine TBW. **False** ## References 1. Barrett KE, Barman SM, Brooks HL, and Yuan JX. (2019). Ganong's Review of Medical Physiology. 26th ed. ebook by McGraw-Hill Education. 2. Hall JE, and Hall ME. (2021). Guyton and Hall Textbook of Medical Physiology. 14th ed. eBook by Elsevier, Inc. 3. Sherwood L, (2016). Human Physiology From Cells to Systems. 9th ed. eBook by Nelson Education, Ltd. ## It's so lovely to meet all of you! - Thank you for listening.