![]() ![]() Therefore, it should be remembered that both the ECF found in plasma and the ICF found in erythrocytes, contribute to the total blood volume. It should be pointed out that the plasma volume is not the same as the blood volume, as the volume of erythrocytes contributes nearly 40% of the entire blood's volume. As mentioned, the plasma is separated from the interstitial fluid by the vascular wall which is permeable to water and small solutes but not proteins. The plasma refers to the total volume of ECF within the vascular space.Consequently, the interstitial fluid is composed of roughly the same chemical composition as the plasma except without the proteins. As described in microcirculatory physiology, the vasculature allows free movement of water and small solutes but not of proteins. The Interstitial Fluid refers to the total volume of ECF outside of the blood vessels and is separated from the plasma (see below) by the walls of the body's vasculature.These compartments are separated by the vasculature. The ECF is sub-divided into two other fluid compartments known as the Interstitial Fluid and the Plasma. The ECF contains roughly one-third of the total body water or about 20% of total body weight. As mentioned before, the ECF is separated from the ICF by the plasma membrane of each cell which is impermeable to nearly all classes of solutes. The Extracellular Fluid (ECF) refers the total volume of fluid outside of cells.The ICF contains roughly two-thirds of the total body water or about 40% of total body weight. Although the plasma membrane is permeable to water, it is highly impermeable to both ionic and small solutes as well as proteins. The ICF is separated from the Extracellular Fluid (see below) by the plasma membrane of each, individual cell. The Intracellular Fluid (ICF) refers to the fluid present inside cells and is considered the sum total of the fluid volume in all of the body's cells. ![]() The vascular wall is permeable to water and small solutes but not proteins. The plasma membrane is permeable to water but not small solutes or proteins. Each of these compartments is separated by the barriers shown above with unique physio-chemical properties. The ECF is itself divided between fluid within the vasculature itself, known as plasma, and that outside the vasculature, known as the interstitial fluid. The remainder is within the extracellular space as the Extracellular Fluid (ECF). Two-thirds of total body water is held within cells as Intracellular Fluid (ICF). Roughly 60% of the total body weight is water. OL Lab 5: Fluid balance, acid base balance and water balance Leaming Objectives: Identify the functions and the location of the major fuld compartments of the body Explain the regulation of water balance in order to maintain homeostasis Identify the proportions of electrolytes found in the plasma, interstitial fluid. Below we discuss how these compartments are defined, the nature of their separating barrier, and how much of the fluid volume each compartment contains in a healthy individual. In a healthy individual, fluid is divided between these functional compartments in certain ratios. Fluid within the body can be thought of as separated into several functional compartments divided by semi-permeable membranes which allow free movement of water but not of certain classes of solutes.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. 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. ![]()
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