WATER

     WATER : LARGEST CONSTITUENT OF HUMAN BODY :

%age consistence of water in humans :

• Water is essential for life.
• Without food one can survive for about a month,but in the absence of  water for a few days.
• The significance of water is evident from the fact that it is the largest constituent of the human body
• .More than 60% weight of an adult man is water.
• Women contain 45 to 55% since they have more fat,which is drier(20% water)than muscles(75%)
• Babies contain more water than adults do and the elderly slightly less.
• Most of it(about 55 % ) is held inside the cells as intracellular fluid,while the rest(about 45%)is contained in the extracellular fluid.
• Relatively little,about 7.5% of the total water,is in blood stream that forms part of the extracellur fluid.These fluids are in a dynamic state since they constantly undergo changes in composition.
• Nutrients and oxygen are taken up by the cells that in turn excrete carbon dioxide and other waste materials.
• Inspite of this,composition of various body fluids remains almost constant.

             FUNCTIONS OF WATER IN HUMAN BODY :

Water is required in the body primarily to perform some important functions,as briefly discussed below :

1. As a building material in every cell~~fatty tissues contain 20% , bone 26 % and striated muscles 75% water.
2. As a lubricant in joints and between the internal organ.
3. Help to regulate the body temperature.
4. Serve as a medium for nutrients,enzymes and other chemical substances to be dissolved or dispersed.
5. As a medium for intercellular reactions to take place.
6. As a hydrolyzer.
7. As a transport medium for carrying nutrients to cells and removing wastes from he body.

                          SOURCES OF WATER IN BODY :

There are three major sources of water supply in the body :

A.Daily diet supplies

B.Metabolic reactions

C.Intake of drinks

A.Daily diet supplies :

Daily diet supplies 750ml to 1000ml water(about 25 to 35% of the intake)

B.Metabolic reactions :

Water produced in the body as a result of metabolic activity(utilization of nutrients)supplies from 10 to 15% of the daily intake.this water comes from REDOX reactions.thus,when 1g of carbohydrate,fat,and protein are oxidized in the body,o.6 , 1.07 and 0.41g water is produced,respectively.

 C.Intake of drinks :

Water taken as drinks (drinking water,beverages,fruit juices,tea,coffee,milk etc)account for 50% or more of the daily intake.

                         WATER LOSS FROM THE BODY :

Water loss from the body occurs through

• lungs(with respiration
• skin(as sweat&perspiration)
• kidneys(as urine
• digestive tract(in faeces)

THROUGH LUNGS&SKIN :

Insensible loss,also known as transpiration,occurs both through the expired air and skin.It's rate is associated with temperature and humidity.Almost 400ml water is lost in respiration,while about the same quantity is lost through the skin under all conditions.

losses vary greatly with perspiration depending upon activity,temperature and humidity.this may range from a minimum of 200ml in cool climate to about 4L in hot climate.In hot climates a physical labourer may lose upto 14L water per day.In case of severe perspiration,sodium depletion is very likely to occur.

THROUGH DIGESTIVE TRACT&KIDNEYS :

• A loss of 100 to 200ml occurs through feaces.The major route of water excretion is through the kidneys as urine.The kidneys ilter about 180L water per day.However,water lost through urine varies from 1000 to 2000mL per day.
• Losses are replaced with liberal drinking of beverages.
• When water losses are more through perspiration,drinking water or other beverages containing common salt is advisable to replenish sodium loss.