Drinking is the act ofingestingwater or otherliquids into the body through themouth,proboscis, or elsewhere. Humans drink byswallowing, completed byperistalsis in theesophagus. The physiological processes of drinking vary widely among otheranimals.
Most animalsdrink water to maintainbodily hydration, although many can survive on the water gained from their food. Water is required for manyphysiological processes. Both inadequate and (less commonly) excessive water intake are associated with health problems.
When aliquid enters a humanmouth, theswallowing process is completed byperistalsis which delivers the liquid through theesophagus to thestomach; much of the activity is abetted by gravity. The liquid may be poured from the hands ordrinkware may be used as vessels. Drinking can also be performed by acts ofinhalation, typically when imbibing hot liquids or drinking from a spoon. Infants employ a method of suction wherein the lips are pressed tight around a source, as inbreastfeeding: a combination of breath and tongue movement creates a vacuum which draws in liquid.[1]
By necessity,terrestrial animals in captivity become accustomed to drinking water, but most free-roaming animals stay hydrated through the fluids and moisture in fresh food,[2] and learn to actively seek foods with high fluid content.[3] When conditions impel them to drink from bodies of water, the methods and motions differ greatly among species.[4]
Cats,canines, andruminants all lower the neck and lap in water with their powerful tongues.[4] Cats and canines lap up water with the tongue in a spoon-like shape.[5] Canines lap water by scooping it into their mouth with a tongue which has taken the shape of a ladle. However, with cats, only the tip of their tongue (which is smooth) touches the water, and then the cat quickly pulls its tongue back into its mouth which soon closes; this results in a column of liquid being pulled into the cat's mouth, which is then secured by its mouth closing.[6] Ruminants and most other herbivores partially submerge the tip of the mouth in order to draw in water by means of a plunging action with the tongue held straight.[7] Cats drink at a significantly slower pace than ruminants, who face greater natural predation hazards.[4]
Manydesert animals do not drink even if water becomes available, but rely on eatingsucculent plants.[4] In cold and frozen environments, some animals likehares,tree squirrels, andbighorn sheep resort to consuming snow and icicles.[8] Insavannas, the drinking method ofgiraffes has been a source of speculation for its apparent defiance of gravity; the most recent theory contemplates the animal's long neck functions like aplunger pump.[9] Uniquely,elephants draw water into their trunks and squirt it into their mouths.[4]
There are three general ways in which birds drink: using gravity itself, sucking, and by using the tongue. Fluid is also obtained from food.
Most birds are unable to swallow by the "sucking" or "pumping" action ofperistalsis in theiresophagus (as humans do), and drink by repeatedly raising their heads after filling their mouths to allow the liquid to flow by gravity, a method usually described as "sipping" or "tipping up".[10]The notable exception is the family of pigeons and doves, theColumbidae; in fact, according toKonrad Lorenz in 1939:
one recognizes the order by the single behavioral characteristic, namely that in drinking the water is pumped up by peristalsis of the esophagus which occurs without exception within the order. The only other group, however, which shows the same behavior, thePteroclidae, is placed near the doves just by this doubtlessly very old characteristic.[11]
Although this general rule still stands, since that time, observations have been made of a few exceptions in both directions.[10][12]
In addition, specializednectar feeders like sunbirds (Nectariniidae) and hummingbirds (Trochilidae) drinkby using protrusible grooved or trough-like tongues, and parrots (Psittacidae) lap up water.[10]
Many seabirds have glands near the eyes that allow them to drink seawater. Excess salt is eliminated from the nostrils. Many desert birds get the water that they need entirely from their food.The elimination of nitrogenous wastes as uric acid reduces the physiological demand for water,[13] as uric acid is not very toxic and thus does not need to be diluted in as much water.[14]Most birds scoop or draw water into thebuccal areas of their bills, raising and tilting their heads back to drink. An exception is the commonpigeon, which can suck in water directly by inhalation.[4]
Most insects obtain adequate water from their food: When dehydrated from a lack of moist food, however, many species will drink from standing water.[15] Additionally, all terrestrial insects constantly absorb a certain amount of the air's humidity through theircuticles.[15] Some desert insects, such asOnymacris unguicularis, have evolved to drink substantially from nighttime fog.[15]
Amphibians andaquatic animals which live infreshwater do not need to drink: they absorb water steadily through the skin byosmosis.[4][16]Saltwater fish, however, drink through the mouth as they swim, and purge the excess salt through the gills.[16] Saltwater fishes do drink plenty of water and excrete a small volume of concentrated urine.
Like nearly all other life forms, humans require water fortissue hydration. Lack of hydration causesthirst, a desire to drink which is regulated by thehypothalamus in response to subtle changes in the body'selectrolyte levels and blood volume. A decline in totalbody water is calleddehydration and will eventually lead to death byhypernatremia. Methods used in themanagement of dehydration include assisted drinking ororal rehydration therapy.
An overconsumption of water can lead towater intoxication, which can dangerously dilute the concentration of salts in the body. Overhydration sometimes occurs among athletes and outdoor laborers, but it can also be a sign of disease or damage to the hypothalamus. A persistent desire to drink inordinate quantities of water is a psychological condition termedpolydipsia. It is often accompanied bypolyuria and may itself be a symptom ofdiabetes mellitus ordiabetes insipidus.[17]
_---_European_Space_Agency_(ESA)_astronaut_Thomas_Reiter.jpg)
A daily intake of water is required for the normal physiological functioning of thehuman body. TheUSDA recommends a daily intake oftotal water: not necessarily by drinking but by consumption of water contained in otherbeverages and foods. The recommended intake is 3.7 liters (appx. 1 gallon) per day for an adult male, and 2.7 liters (appx. 0.75 gallon) for an adult female.[18]
Other sources, however, claim that a high intake of freshdrinking water, separate and distinct from other sources of moisture, is necessary for good health – eight servings per day of eight fluid ounces (1.8 liters, or 0.5 gallon) is the amount recommended by manynutritionists,[19] although there is no scientific evidence supporting this recommendation.[20][21]
Evidence-based hydration experts say that the amount of drinking water needed depends on ambient temperature, activity level, body size, and sweat rate.[22] Research shows drinking when thirsty will maintain hydration to within about 2% of the needed level.[22] Drinking beyond thirst might be beneficial for people who need to perform tasks that require intense concentration, and those withkidney disease,kidney stones,urinary tract infections, and people with a weak sense of thirst (which may include more older people).[22]
The term "drinking" is often usedmetonymically for the consumption ofalcoholic beverages. Most cultures throughout history have incorporated some number of thewide variety of "strong drinks" into their meals, celebrations, ceremonies,toasts and other occasions.[23] Evidence offermented drinks in human culture goes back as early as theNeolithic Period,[24] and the first pictorial evidence can be found in Egypt around 4,000 BC.[25]
Alcohol consumption has developed into a variety of well-establisheddrinking cultures around the world. Despite its popularity, alcohol consumption poses significant health risks.Alcohol abuse and the addiction ofalcoholism are common maladies in developed countries worldwide.[26] A high rate of consumption can also lead tocirrhosis,gastritis,gout,pancreatitis,hypertension, various forms ofcancer, and numerous other illnesses.[27]
