![]() ![]() D 2O and H 3O are distributed in the body exactly like water. Tritiated water (H 3O or HTO) and deuterium oxide (D 2O) -the two isotopes are often used for the determination of total body water. The result will be valid only when the drug will be mixed thoroughly. Suppose 35 mg of dye has been added and the final concentration that has been achieved to be 0.07 mg per ml, then the volume of the beaker will be ![]() If the final concentration of the dye is determined by the calorimeter then the volume capacity of the beaker can be determined. If a beaker of unknown capacity is taken, then its volume can be determined by mixing uniformly a known amount of dye in the volume of water present in the beaker. ![]() E.g., if a known quantity of dye-Q is taken and the final concentration is achieved as C, then the volume of distribution V will be V = (Q/C). In this technique the amount of dye used, the final concentration of the dye in the solution is made, are considered for determining the volume of distribution. Volume of water present in each compartment cannot be measured directly and thus indirect method-the dilution technique has been adopted for its determination. Total body water and extracellular water can be measured by dilution technique with varying degree of precisions. This intracellular fluid contains about 30-40% of the body weight and holds about 55% of the whole body water. In a cell there are many anatomic subdivisions and for this reason there is a striking difference in water content and ionic composition in between the cytoplasm, nucleus, mitochondria and microsomes of various cell types. It is neither a continuous nor a homogeneous phase and represents the sum of the fluid contents of all the cells of the body. Plasma water that is confined within the vascular system- 7.5 percent. Dense connective tissue and cartilage water- 7.5 percent. The extracellular fluid phase can be divided into following sub compartments: It is postulated that 55% of water is present in the intracellular space and the rest in the extracellular space. Edelman and Leibman (1959) have studied thoroughly the distribution pattern of body water by dilution technique and also by tissue analysis. The extracellular fluid compartment is a compartment containing heterogenous collections of fluids and not a continuous fluid phase. The cell membrane actually provides the boundary in between the extracellular and the intracellular compartments. The distribution of body water in different compartments has been presented schematically in Fig. The water of the body can be considered to be distributed within two main compartments-the extracellular and the intracellular. The percentage of water in various tissues and the proportion of total weight of the body which each tissue represents, have been presented in Table 5.3. Besides this, the relative distribution of water in the various organs and tissues is mostly same in man as well as in other species. It has been observed after studying thoroughly the water content of the body in man as well as in different animal species that the total water content in man is similar to that of in other animals. The average water content in different tissues of the body has been presented in Table 5.1. Mitchell and his associates (1945), Wid-dowson and his co-workers (1951) have also determined the water content of the human beings by direct method. In 1863 Bischoff determined the water content of an executed criminal by the method of desiccation. The total body water content can be determined most accurately by the process of desiccation. In general, woman contains more fat than man. In lean person, the value is higher than that of in obese person. But the above values vary mostly with the relative degrees of leanness and fatness of the individual. In human being it is about 65% of the body weight in males and about 10% less in females. ![]() Total body water in an average human being, weighing about 70 kg is 40 litres to 45 litres. ![]()
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