water and electrolyte balance

• Water is an essential nutrient as important to life as any of the others and can only be survived for a few days without it, whereas a deficiency of nutrients may take weeks, months or even years to develop.
• In the body, water becomes the fluid in which all life processes occur.
• Every cell contains intracellular fluid and is bathed externally in another such as interstitial fluid.
• Water compartments include intracellular fluid, extracellular fluid (ECF), intravascular, and interstitial.
• Water functions as a solvent, reactant, lubricant, temperature regulator, and provider of dietary nutrients.
• Water is the solvent of life, making many solutes available for all cell functions and serving as a medium needed for all reactions.
• Water is essential for the physiologic process of digestion, absorption, metabolism, and excretion.
• Water participates as a substrate in metabolic reactions.
• Water functions as a reactant that participates in chemical reactions such as condensation and hydrolysis.
• Principal buffers of the blood include Bicarbonate - carbonic acid system and Phosphate system.
• An alteration in the maintenance of osmotic equilibrium results in dehydration or edema.
• Changes in the electrolyte concentrations in the extracellular fluid result in a shift in water from one compartment to another.
• Stable electrochemical neutrality in the body fluid solutions is maintained by the distribution.
• Cations (+) in the extracellular fluid include Sodium (Na + ), Potassium (K + ), Magnesium (Mg 2+ ), and Calcium (Ca 2+ ).
• Osmotic pressure causes water to pass across the semipermeable membrane from the less concentrated to the more concentrated solution, equalizing the dissolved particles on both compartments.
• Anions (-) in the extracellular fluid include Chloride (Cl - ), Bicarbonate (HCO 3 - ), Phosphate (HPO 4 - ), and Sulfate (SO 4 - ).
• Water serves as a lubricant in synovial fluid and facilitates movement of joints.
• Water facilitates the passage of food down the esophagus in saliva and ocular fluid.
• Water acts as a temperature regulator, excess body heat leading to evaporation.
• Water acts as an insulator, reducing the speed at which heat can be lost from the body.
• Metabolic water is produced as part of the oxidation of foods in the body, with the amount of metabolic water produced varying with different nutrients.
• An additional 500 ml or more or less of urinary fluid excretion is possible.
• 100 g of fat produce 107 ml of water.
• Urinary fluid excretion can also be facultative, depending on the tubular resorption rate and fluctuating body needs.
• Water balance is maintained through intake and excretion.
• Metabolic water contributes about 200 to 300 ml daily.
• Urinary fluid excretion is obligatory, meaning it is the minimum necessary to remove the waste materials to be excreted in the urine.
• 100 g of CHOs produce 55 ml of water.
• 100 g of CHON produce 41 ml of water.
• Feces contribute to water loss, with a loss of water amounts to 200 ml.
• Respiratory water loss, via the lungs, contributes to water loss, with a loss of water amounts to a little over 300 ml.
• Perspiration, via the skin, contributes to water loss, with a loss of water amounts to 350 - 700 ml/day.
• Water provides dietary nutrients, with 1L of hard water contributing 50 mg Ca and 120 mg Mg, and 1L of soft water contributing 250 mg Na.
• Renin-angiotensin system causes kidneys to retain sodium and water, rising electrolyte concentration in ECF stimulates increased water intake and water reabsorption by the kidneys.
• About 900 ml daily for an adult is the requirement for water intake.
• Body weight is a factor in fluid requirement, a younger individual needs greater per unit of body weight.
• Pregnant women require 30 ml/kg body weight or ≥ 300 ml/day of water, which is more than that of non-pregnant, non-lactating individuals.
• Extravascular fluid volume deficit (HYPOvolemia or DEhydration) is caused by sudden decrease in fluid intake, acute loss of secretion, or increased volume of excretions from the body.
• Non-electrolytes do not ionize, examples include Glucose, Alcohol, Urea, Protein.
• Hormonal control of water excretion involves Antidiuretic hormone (ADH) or Vasopressin which is secreted by the pituitary gland, increased water reabsorption occurs when ADH is increased.