Thus, Subject A has a blood pH of 7.19 computed from the, and Subject B has a reported blood pH of 7.3. To compare the acidity of the blood of each subject, convert the for Subject A to pH as follows: Which subject has the higher concentration of H + in his blood?

Subject A has an arterial of 65 × 10 −9 Eq/L, and Subject B has an arterial pH of 7.3. The laboratory reports the acidity of Subject A’s blood in terms of and the acidity of Subject B’s blood in terms of pH. Two men, Subject A and Subject B, have disorders that cause excessive acid production in the body. The negative sign means that pH decreases as the concentration of H + increases, and pH increases as the concentration of H + decreases. Thus, Because the H + concentration of body fluids is very low (e.g., 40 × 10 −9 Eq/L in arterial blood), it is more conveniently expressed as a logarithmic term, pH. PH is a logarithmic term that is used to express hydrogen (H + ) concentration. For example, a solution containing 1 mmol/L NaCl is 2 mOsm/L because NaCl dissociates into two particles. If a solute dissociates into more than one particle in solution (e.g., NaCl), then its osmolarity equals the molarity multiplied by the number of particles in solution. If a solute does not dissociate in solution (e.g., glucose), then its osmolarity is equal to its molarity. Osmolarity is the concentration of particles in solution expressed as osmoles per liter. One osmole is the number of particles into which a solute dissociates in solution. Likewise, one mole of calcium chloride (CaCl 2 ) in solution dissociates into two equivalents of calcium (Ca 2+ ) and twoequivalents of chloride (Cl − ) accordingly, a Ca 2+ concentration of 1 mmol/L corresponds to 2 mEq/L. For example, one mole of potassium chloride (KCl) in solution dissociates into one equivalent of potassium (K + ) and one equivalent of chloride (Cl − ). A glucose concentration of 1 mmol/L has 1 × 10 −3 moles of glucose in 1 L of solution.Īn equivalent is used to describe the amount of charged (ionized) solute and is the number of moles of the solute multiplied by its valence. One mole is 6 × 10 23 molecules of a substance. In biologic solutions, concentrations of solutes are usually quite low and are expressed in millimoles per liter (mmol/L), milli equivalents per liter (mEq/L), or milli osmoles per liter (mOsm/L). Likewise, concentrations of solutes are expressed in moles per liter (mol/L), equivalents per liter (Eq/L), or osmoles per liter (Osm/L). Typically, amounts of solute are expressed in moles, equivalents, or osmoles. Units for Measuring Solute Concentrations There are also certain predictable differences in solute concentrations between plasma and interstitial fluid that occur as a result of the exclusion of protein from interstitial fluid. ICF and ECF have vastly different concentrations of various solutes. The composition of the body fluids is not uniform. The method for estimating the volume of the body fluid compartments is presented in Chapter 6. Because the capillary wall is virtually impermeable to large molecules such as plasma proteins, interstitial fluid contains little, if any, protein. Interstitial fluid is an ultrafiltrate of plasma, formed by filtration processes across the capillary wall. Plasma and interstitial fluid are separated by the capillary wall. Interstitial fluid is the fluid that actually bathes the cells and is the larger of the two subcompartments. Plasma is the fluid circulating in the blood vessels and is the smaller of the two ECF subcompartments. The ICF is contained within the cells and is two thirds of total body water the ECF is outside the cells and is one third of total body water. ICF and ECF are separated by the cell membranes.ĮCF is further divided into two compartments: plasma and interstitial fluid. Total body water is distributed between two major body fluid compartments: intracellular fluid (ICF) and extracellular fluid (ECF) ( Fig.

The distribution of water among body fluid compartments is described briefly in this chapter and in greater detail in Chapter 6. Because females have a higher percentage of adipose tissue than males, they tend to have less body water. Thus, total body water is a higher percentage of body weight when body fat is low and a lower percentage when body fat is high. In general, total body water correlates inversely with body fat. For example, a 70-kilogram (kg) man whose total body water is 65% of his body weight has 45.5 kg or 45.5 liters (L) of water (1 kg water ≈ 1 L water). The total amount of fluid or water is called total body water, which accounts for 50% to 70% of body weight. In the human body, water constitutes a high proportion of body weight. VOLUME AND COMPOSITION OF BODY FLUIDSĭistribution of Water in the Body Fluid Compartments

Body fluid compartments dunnet