dehydration

(noun)

In physiology and medicine, dehydration (hypohydration) is defined as the excessive loss of body fluid.

Related Terms

Examples of dehydration in the following topics:

  • Water Balance Disorders

    • In physiology and medicine, dehydration (hypohydration) is defined as the excessive loss of body fluid.
    • Much of the physiological effects of dehydration is due to the changes in ion concentration that may occur as a result of the dehydration.
    • Hypotonic dehydration causes decreased plasma osmolarity, while hypertonic dehydration will cause increased plasma osmolarity.
    • Isotonic dehydration is the most common type of dehydration.
    • Intravenous administration of fluid is one effective treatment of dehydration in humans.

  • Dehydration Synthesis

    • In dehydration synthesis, monomers combine with each other via covalent bonds to form polymers.
    • Thus, the monomers that are joined together are being dehydrated to allow for synthesis of a larger molecule.
    • As additional monomers join via multiple dehydration synthesis reactions, the chain of repeating monomers begins to form a polymer.
    • Three of the four major classes of biological macromolecules (complex carbohydrates, nucleic acids, and proteins), are composed of monomers that join together via dehydration synthesis reactions.
    • These three are polysaccharides, classified as carbohydrates, that have formed as a result of multiple dehydration synthesis reactions between glucose monomers.

  • Sodium, Electrolytes, and Fluid Balance

    • Chronic laxative abuse or severe diarrhea or vomiting (gastroenteritis) can lead to electrolyte disturbances along with dehydration.
    • In humans, the most common type of dehydration by far is isotonic (isonatraemic) dehydration which effectively equates with hypovolemia; but the distinction of isotonic from hypotonic or hypertonic dehydration may be important when treating people with dehydration.
    • In hypotonic dehydration, intravascular water shifts to the extravascular space, exaggerating intravascular volume depletion for a given amount of total body water loss.
    • In more severe cases, correction of a dehydrated state is accomplished by the replenishment of necessary water and electrolytes (through oral rehydration therapy or fluid replacement by intravenous therapy).
    • As oral rehydration is less painful, less invasive, less expensive, and easier to provide, it is the treatment of choice for mild dehydration.

  • Other Reactions

    • One practical application of this behavior lies in the dehydration of 1º-amides to nitriles by treatment with thionyl chloride.
    • Other dehydrating agents such as P2O5 effect the same transformation.

  • Hydrolysis

    • These reactions are in contrast to dehydration synthesis (also known as condensation) reactions.
    • In dehydration synthesis reactions, a water molecule is formed as a result of generating a covalent bond between two monomeric components in a larger polymer.
    • Dehydration and hydrolysis reactions are chemical reactions that are catalyzed, or "sped up," by specific enzymes; dehydration reactions involve the formation of new bonds, requiring energy, while hydrolysis reactions break bonds and release energy.
    • This is the reverse of the dehydration synthesis reaction joining these two monomers.
    • This is the reverse of the dehydration synthesis reaction joining these two monomers.

  • Elimination Reactions of Alcohols

    • The elimination of water from an alcohol is called dehydration.
    • The last two reactions also demonstrate that the Zaitsev Rule applies to alcohol dehydrations as well as alkyl halide eliminations.
    • It should be noted that the acid-catalyzed dehydrations discussed here are the reverse of the acid-catalyzed hydration reactions of alkenes.
    • The dehydration reaction is shown by the blue arrows; the hydration reaction by magenta arrows.
    • The first equation shows the dehydration of a 3º-alcohol.

  • Waxes

    • The leaves and fruits of many plants have waxy coatings, which may protect them from dehydration and small predators.

  • Preparation of Ethers

    • Acid-catalyzed dehydration of small 1º-alcohols constitutes a specialized method of preparing symmetrical ethers.

  • Hormonal Regulation of the Excretory System

    • Maintaining a proper water balance in the body is important to avoid dehydration or over-hydration (hyponatremia).
    • Dehydration or physiological stress can cause an increase of osmolarity above threshold levels, which, in turn, raises ADH secretion and water retention, causing an increase in blood pressure.
    • ADH release can be reduced by certain substances, including alcohol, which can cause increased urine production and dehydration.
    • If the condition is not severe, dehydration may not occur, but severe cases can lead to electrolyte imbalances due to dehydration.

  • Pylorospasm and Pyloric Stenosis

    • Dehydration also can occur causing the infant to cry without having tears, and having less wet or dirty diapers (hours up to a couple days without a dirty/wet diaper).
    • The danger of pyloric stenosis comes from the dehydration and electrolyte disturbance rather than the underlying problem itself.
    • Therefore, the baby must be initially stabilized by correcting the dehydration and hypochloremic alkalosis with IV fluids.