![]() 1/3 times 54 liters gives us 18 liters of extracellular fluid. Two thirds times 54 liters gives us 36 liters of intracellular fluid. This gives us a total body water of 54 liters. In this case, we will multiply the total body weight by 0.6. Now let us consider an individual who weighs 90 kilograms and has high muscle mass. Thus, three fourths times 11.7 gives us 8.75 litres of interstitial fluid and the remaining fourth or 3 liters would be the intravascular fluid. Three fourths of the extracellular fluid is interstitial fluid. 1/3 of the total body water is extracellular so, 1/3 times 35 liters is about 11.7 liters. Therefore, we calculate two thirds times 35 liters and find it to be 23.3 liters. Two thirds of the total body water is intracellular. First we calculate the total body water to be 35 liters. Because this individual shown has normal muscle mass, we will multiply the body weight by 0.5. Let's do some examples, starting with an individual that weighs 70 kilograms. Therefore, when we refer to the extracellular intravascular fluid, it is the portion that does not include circulating red blood cells. ![]() Hematocrit, which is made up of red blood cells is normally 45% of the total circulating fluid volume and is technically part of the intracellular fluid. It is important to note the exclusion of hematocrit in this category. The remaining quarter of the extracellular fluid is composed of the intravascular fluid, or IVF, which is the circulating fluid contained in arteries and veins. Three quarters of the extracellular fluid is composed of interstitial fluid, which is the fluid taking up the space in between cells. Extracellular meaning the fluid surrounding these cells.Įxtracellular fluid can be further broken down into two categories, interstitial and intravascular. Intracellular, meaning the cytoplasmic fluid inside of cells. Two thirds of total body water is intracellular and 1/3 is extracellular. Now that you can estimate total body water, let's talk about how it is distributed. Because each person is different, you should use clinical judgment when deciding which formula to use based on muscle mass. That would make their total body water about 35 liters or 50% of body weight. That is approximately 60% of the total body weight.Īlternatively, these individuals who have less muscle mass weigh 70 kilograms. Using the formula we calculate that their total body water is about 54 liters. These muscular individuals have a weight of 90 kilograms. To estimate total body water for a person with low muscle mass, calculate 0.5 times the total body weight. To estimate total body water for a person with high muscle mass, calculate 0.6 times the total body weight. In order to study body fluid, we need to determine an estimate of total body water. Knowing the basics of water and solute balance in the various body fluid compartments is critical to managing patients with fluid balance disorders. There are a wide variety of solutes in our body, and each solute behaves differently when it is dissolved in our body fluid. For a complete diagram of body fluid compartments, see body fluid compartments of a 70-kg man and body fluid compartments of a 55-kg woman.The simplest way to think about the body is to recognize that for the most part, it is simply a whole bunch of particles dissolved into a solution of water. Note that this diagram places focus only on these three major fluid compartments. Plasma is the smallest fluid compartment (~8% of total body water). Interstitial fluid contains ~25% of the total body water. The intracellular fluid compartment contains most of the water in the body (~67% of total). ![]() ![]() The right diagram shows the three major fluid compartments drawn to scale. The left diagram allows for a better demonstration of the relationship between the intracellular fluid, interstitial fluid, and plasma, however, the relative size of each of the compartment is not drawn to scale. Waste products produced by cells follow the reverse path from the cytoplasmic compartment to plasma. They then must cross the plasma membrane to enter the cytoplasmic compartment of cells. Nutrient molecules traveling in the blood must first cross the capillary endothelium to enter the interstitial fluid. The capillary endothelium is the physical barrier that separates the interstitial fluid from plasma. The physical barrier separating the intracellular fluid compartment (i.e., cytoplasm) and the interstitial fluid is the cell plasma membrane. Fluid, molecules, and ions flow across physical barriers between the fluid compartments. These are the (1) intracellular fluid compartment, (2) interstitial fluid, and (3) plasma. In the human body plan, there are three major fluid compartments that are functionally interconnected.
0 Comments
Leave a Reply. |