WATER

 

INTRODUCTION: Water makes up 60% to 75% of the human body, and is essential to life for several reasons:  1) Water is a solvent; that is, many substances called solutes, can dissolve in water. Nutrients such as glucose are dissolved in blood plasma, which is largely water, to be transported to cells throughout the body. The sense of taste depends upon the solvent ability of saliva; dissolved food stimulates the receptors in taste buds. The excretion of waste products is possible because they are dissolved in the water of urine.

2) Water is a lubricant, which prevents friction where surfaces meet and move. In the digestive tract, swallowing depends upon the presence of saliva, and mucus is a slippery fluid that permits the smooth passage of food through the intestines. Synovial fluid within joint cavities prevents friction as bones move.

3) Water changes temperature slowly. Water has a high heat capacity, which means that it will absorb a great deal of heat before its temperature rises significantly, or it must lose a great deal of heat before its temperature drops significantly. This is one of the factors that helps the body maintain a constant temperature. Water also has a high heat of vaporization, which is important for the process of sweating. Excess body heat evaporates sweat on the skin surfaces, rather than overheating the body’s cells, and because of water’s high heat of vaporization, a great deal of heat can be given off with the loss of a relatively small amount of water.

WATER COMPARTMENTS: All water within the body is continually moving, but water is given different names when it is in specific body locations, which are called compartments.

INTRACELLULAR FLUID (ICF): This is the water within cells; about 65% of the total body water.

EXTRACELLULAR FLUID (ECF): All the rest of the water in the body; about 35% of the total. More specific compartments of extracellular fluid include:

Plasma; water found in blood vessels

Lymph; water found in lymphatic vessels

Tissue fluid or interstitial fluid; water found in the small spaces between cells.

Specialized fluids; synovial fluid, cerebrospinal fluid, aqueous humor in the eye, and others.

RELATED;

1. PLASMA  

2.  BLOOD AND ITS COMPONENTS

3.  ANATOMY AND PHYSIOLOGY

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