L1_Biophysics I_BMS131_Physiology_Lec#_Fall 2024_Prof.Sahar El Agaty vys .pdf

# Body Fluids Compartments and Their Ionic Composition ## Prof. Sahar El Agaty | Professor of Physiology ## Biophysics 1-Physiology Lecture 1 ### Introduction #### Human Physiology: - It is the science that deals with the study of the functions of the human body. - It explains the characteristics a...

# Body Fluids Compartments and Their Ionic Composition ## Prof. Sahar El Agaty | Professor of Physiology ## Biophysics 1-Physiology Lecture 1 ### Introduction #### Human Physiology: - It is the science that deals with the study of the functions of the human body. - It explains the characteristics and mechanisms of the human body that make 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 a basic functions e.g., - Obtaining food (nutrients) and O2 from the environment surrounding the cell. - Performing chemical reactions that use nutrients and O2 to provide energy for the cells, as follows: Food + O2 → CO2 + H2O + energy - Eliminating to the cell’s surrounding environment CO2 and other wastes, produced during these chemical reactions. 3. **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. 4. **Organs:** An organ is a unit made up of several tissue types e.g., Stomach 5. **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. 6. **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 | Categories | 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 * The total body mass of a male is 70 kg * 40% of the body weight is made up of solids. * 60% of the body weight is made up of water (42 liters) * The intracellular fluid (ICF) is 2/3 of the total body water (40% of body weight) and is equal to 28 liters. * The extracellular fluid (ECF) is 1/3 of the total body water (20% of body weight) with a total volume of 14 liters. - The intracellular fluid is surrounded by the plasma membrane separating it from the ECF. - The intravascular fluid or plasma is 5% of the body weight, making up 3.5 liters of the total body water. It is found inside the vascular system and is separated from the interstitial fluid by the capillary wall. - The interstitial fluid (ISF) or tissue fluid makes up 15% of the body weight (10.5 liters) and surrounds the cells and is separated from the plasma by the capillary wall. #### Transcellular fluid 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 maintain 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 Difference between ICF and ECF compositions: ### 1. Cations and anions: | Compartment | Cation | Anion | | -------- | -------- | -------- | | ICF | K+ | Phosphates and Proteins | | ECF | Na+ | Cl- and HCO3- | ### 2. Proteins: ICF>plasma>ISF - ICF contains a higher concentration of protein than ECF, as proteins can not 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 small amount of proteins are leaked into the ISF. ## Student Activity #### True and false - Capillary wall is a barrier between ISF and plasma. **T** - Main ICF cation is Na+. **F** - The highest concentration of proteins are found in ICF. **T** ### Body fluids ### Movement of water between different compartments #### 1. Hydrostatic pressure - 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. #### 2. 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 withdraw fluid into the compartment. ### Clinical Note #### Edema: - 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. ### Body Fluids ### ECF as an internal environment: - It is in a constant motion throughout the body, moving between the blood and tissue fluids through the capillary walls. - It contains the ions and nutrients required by the cells to maintain life. - It is the site at which waste products of the cells are eliminated. - The ECF is called the internal environment of the body. ### Measurement Of Body Fluid Compartment Volumes—Indicator-dilution Principle - 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 - The total mass of a substance after dispersion in the fluid compartment = Total mass injected into the compartment. - **Steps** - Inject the substance into the compartment. - Allow the substance to disperse evenly throughout the compartment. - Analyze the concentration of the substance in the compartment. - **Calculation** - Volume (ml) = total amount of substance injected / Cocentration of substance in the dispersed fluid - If the indicator is excreted, you can use the following equation to determine the fluid compartment volume: - Volume (ml) = (total amount of substance injected - amount of substance excerted) / Cocentration of substance in the dispersed fluid ### 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<br> 2. Tritium oxide<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 - ISF=ECF-Plasma - TBW=ICF+ECF - 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). - **Calculation** - **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 - In normal activity and moderate atmospheric temperature, water intake is equal to water output. - **Water gain** - **Sources:** - Food and Drinking (2.2 L/day) - Body oxidative metabolism (0.3 L/day) - **In disease** - Intravenous fluid infusion - **Water loss** - **Sources:** - Urine (1.5 L/day) - Insensible water loss through respiratory tract and skin (0.9L/day) - Stool (0.1 L/day) - **In disease** - Diarrhea and vomiting ### Student Activity #### True and false - Indicator used to measure ECF must cross cell membrane. **F** - ECF is the internal environment of the body. **T** - Evan's blue is used to determine TBW. **F** ### 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.