Chapter 5 :- Water

(A.) Definition:-

Water is so familiar and so large a constituent of the body that its fundamental importance in both structure and functioning of all tissues tends to be overlooked. 
           Water is the most essential constituent of our body. It accounts for 55-70 percent of our total body weight. Men have a higher proportion of water in their body as compared to women. Lean individuals have more than the obese, and infants and children have a greater proportion of water than adults. 
            The total body fluid is distributed among two major compartments:-
  1. The extracellular fluid or water present outside the cells in the interstitial spaces and blood plasma. 
  2. The intracellular fluid or the water present inside the cells. 
  Considering an average of 60 percent of body weight contributed by water, an adult weighing 70 kg has a total body water of 42 litres of which 28 litres is intracellular and 14 litres is extracellular. Of the 14 litres, 11 litres is present as interstitial fluid and 3 litres as plasma. Water present in the body is never plain water but has electrolytes dissolved in it. Similarly, when the body loses water, it loses electrolytes as well. 
        Sodium is the principal electrolyte of the extracellular fluid while potassium is predominant in the intracellular spaces. The normal concentration of ions in the intracellular and extracellular fluids needs to be maintained at all times. This concentration of ions is preserved by a balance between the intake of water and the output or loss of body water. 


(B.) Dietary Sources (visible, invisible):-

Sources: Visible

  • Beverages and liquid foods Hot and cold beverages such as tea ,coffee, milk shakes,fruit juices, and soups are largely made up of water. Both stimulating beverages and refreshing beverages are important sources of water and nutrients. 
  • Water content of solid foods another important source of water is fruits, vegetables, and the water used for cooking food. Solid foods contain varying percentages of water. The water consumed from beverages and solid food amounts to 2,100 ml/day approximately. 
Sources : Invisible 

  • Metabolic water It is synthesized in the body as a result of oxidation of fat,proteins,and carbohydrates, adding to about 200 ml/day.
Oxidation of 100 g fat --> 107 ml water
100 g protein --> 41 ml water 
100 g carbohydrate --> 56 ml water 

The intake of fluid varies among different people and also varies according to the climate, habits,and physical activity on a day-to-day basis. 


(C.) Functions of Water:-
  1. Water quenches thirst and is the most refreshing and cooling of all liquids.
  2. It is a structural component of all cells. In the bone, water is tightly bound, but in most tissues, a constant interchange takes place between the body compartments of water. 
  3. Water is the medium in which all chemical reactions take place. 
  4. It is an essential component of all body fluids such as blood, lymph, cerebrospinal fluid, bile,digestive juices,and urine. 
  5. It acts as a lubricant and helps food to be swallowed and digested food to pass through the gastrointestinal tract.
  6. It acts as a solvent for the products of digestion and helps in transporting these products to different tissues. 
  7. Water regulates body temperature by taking up and distributing heat produced in cells when metabolic reactions take place. 
  8. It helps in excreting waste products of metabolic reactions. 
  9. Water is essential to maintain the turgidity of cells. 

(D.) Role of water in maintaining health (water balance):-

In a normal individual, the maintenance of water balance is archived by adjusting both water intake & excretion as needed.
The major inputs of water are:

  • Fluids that we consume as beverages, including water depending on climatic conditions & habits.
  • Different types of foods & fruits that we take in solid form.
  • Metabolic water.

Output or loss of water from the body:

  • Renal loss: Kidneys excrete about 1-2 liter of water daily
  • Skin: The water loss from the skin is through perspiration.
  • Intestine: A small quantity of water is normally losses in feces.
  • Lungs: The air expired from the lungs also contains water.
  • Sweat: It depends on physical activity & environmental conditions.

Daily intake & output of water

Intakeml/dayOutputml/day
The fluid we take2,200Skin350
From metabolism200Lungs350
Sweat100
Faeces100
Urine1,500
Total2,4002,400


Dehydration:-

It is defined as an excessive loss of body water. It may occur because of inadequate intake of, or abnormal loss of body water or a combination of both.

The symptoms of dehydration are:

  • Thirst
  • Loss of appetite
  • Decreased urination
  • Nausea
  • Impaired temperature regulation
  • Muscular spasms
  • Increased pulse rate

Symptoms of severe dehydration appear when Fluid level falls by more than 10%. A 20% loss of fluid from the body can be fatal.

A dehydrated person is usually managed by Oral Rehydration Therapy (ORT). The WHO recommended ORS (Oral Rehydration Salt) that are to be dissolved in 1 liter of water & make an Oral Rehydration Solution & have to be finished within 24 hours. He also can take HAF. (Home Available Fluid)

Home Available Fluid:-

Normally we prepared in home 1 glass of water + 2 spoon sugar + a pinch of salt + few drops of lime juice (lime juice contained potassium & salt contain sodium which helps to maintain the equilibriums among intracellular & extracellular fluid.)

ORS (WHO) for 1 liter

Contentamount in gm
Glucose20.0
Sodium Chloride (salt)3.5
Sodium bicarbonate (baking soda)1.5
Potassium chloride1.5


Retention of water:-
A minimum of 6-8 glasses of water is recommended to enable the body to perform optimally and keep one active and refreshed throughout the day.

Daily Requirement:-

Excess of water causes oedema. (Swelling of the skin). Oedema is the retention of salt and water in the interstitial fluid giving rise to swelling of skin.


Key Terms:-
  • DNS :- Dextrose Normal Saline is an intravenous fluid containing 5 percent dextrose and 0.9 percent normal saline. 
  • Electrolyte:- A chemical element or compound that dissociates into ions when in solution. 
  • Interstitial fluid:- Fluid present in the spaces or interstices between the cells and tissues in an organ.
  • Oedema:- The accumulation of large amount of fluid in extracellular spaces. 
  • ORS :- Oral Rehydration Salts are a mixture of electrolytes and glucose used for ORT.
  • ORT :- Oral Rehydration Therapy is used for treatment of dehydration by orally feeding fluids to which sugar and salt are added. 


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