DISTRIBUTION AND COMPOSITION OF BODY WATER

Everybody drink water every day but did you know how much of water countain your bady ?

In normal persons adult, the total body water constitutes 50–60% of lean bodyweight in men and 45–50% in women. In a healthy 70 kg male, total body water is approximately 42 L.This is contained in three major compartments:■ intracellular fluid (28 L, about 35% of lean bodyweight)■ extracellular – the interstitial fluid that bathes the cells(9.4 L, about 12%)■ plasma (also extracellular) (4.6 L, about 4–5%).
In addition, small amounts of water are contained in bone, dense connective tissue, and epithelial secretions, such as the digestive secretions and cerebrospinal flid. The intracellular and interstitial flids are separated by the cell membrane; the interstitial flid and plasma are separated
by the capillary wall (Fig. 12.1). In the absence of solute, water molecules move randomly and in equal numbers in either direction across a permeable membrane. However, if solutes are added to one side of the membrane, the inter molecular cohesive forces reduce the activity of the water molecules. As a result, water tends to stay in the solute containing compartment because there is less free diffusion across the membrane. This ability to hold water in the compartment can be measured as the osmotic pressure.