question: Why do your eyes water after you yawn?
comment: I don’t think it happens to everyone, or all the time, but i have heard two things. One: it’s because your yawn stretches your face and contorts your eye sockets, essentially squeezing out tears from the ducts. And two: it’s a reflex because when you’re tired you don’t blink as much and your eyes dry out
passages: found also with "-n-" suffix in Greek χαίνω "to yawn", and without the "-n-" in English "gap" (compare the "figura etymologica" in Norse "ginnunga-gap"), "gum" "palate" and "gasp" (via Old Norse), Latin "hiō, hiatus", and Greek "chasm, chaos".
  
  The Latin term used in medicine is "oscitatio" (anglicized as "oscitation"), from the verb "oscito" "to open the mouth". 
  
  "Pandiculation" is the act of yawning and stretching simultaneously.
  
  Section::::Proposed causes.
   One study states that yawning occurs when one's blood contains increased amounts of carbon dioxide and therefore becomes in need of the influx of oxygen (or expulsion of carbon dioxide) that a yawn can provide. Yawning may, in fact, reduce oxygen intake compared to normal respiration. However, neither providing more oxygen nor reducing carbon dioxide in air decreased yawning.
   Water in the eye can alter the optical properties of the eye and blur vision. It can also wash away the tear fluid—along with it the protective lipid layer—and can alter corneal physiology, due to osmotic differences between tear fluid and freshwater. Osmotic effects are made apparent when swimming in freshwater pools, because the osmotic gradient draws water from the pool into the corneal tissue (the pool water is hypotonic), causing edema, and subsequently leaving the swimmer with "cloudy" or "misty" vision for a short period thereafter. The edema can be reversed by irrigating the eye with hypertonic saline which osmotically draws the excess water out of the eye.
   Another notion states that yawning is the body's way of controlling brain temperature. In 2007, researchers, including a professor of psychology from the University of Albany, proposed yawning may be a means to keep the brain cool. Mammalian brains operate best within a narrow temperature range. In two experiments, subjects with cold packs attached to their foreheads and subjects asked to breathe strictly-nasally exhibited reduced contagious-yawning when watching videos of people yawning. 
   Lacrimal apparatus
  
  The lacrimal apparatus is the physiological system containing the orbital structures for tear production and drainage. It consists of:
  
  BULLET::::- The lacrimal gland, which secretes the tears, and its excretory ducts, which convey the fluid to the surface of the human eye;it is a serous gland located in lacrimal fossae.it is a j shaped gland
  
  BULLET::::- The lacrimal canaliculi, the lacrimal sac, and the nasolacrimal duct, by which the fluid is conveyed into the cavity of the nose, emptying anterioinferiorly to the inferior nasal conchae from the nasolacrimal duct;
   BULLET::::6. changes in the water retaining properties of the tissues themselves. Raised hydrostatic pressure often reflects retention of water and sodium by the kidneys.
   Section::::Detection.:Decreased volume.:Renin-angiotensin system.
   "Crocodile tears syndrome", also known as Bogorad's syndrome, is an uncommon consequence of nerve regeneration subsequent to Bell's palsy or other damage to the facial nerve in which efferent fibres from the superior salivary nucleus become improperly connected to nerve axons projecting to the lacrimal glands, causing one to shed tears (lacrimate) during salivation while smelling foods or eating. It is presumed that this would cause salivation while crying due to the inverse improper connection of the lacrimal nucleus to the salivary glands, but this would be less noticeable.
   There may also be a stringy discharge from the eyes. Although it may seem strange, dry eye can cause the eyes to water. This can happen because the eyes are irritated. One may experience excessive tearing in the same way as one would if something got into the eye. These reflex tears will not necessarily make the eyes feel better. This is because they are the watery type that are produced in response to injury, irritation, or emotion. They do not have the lubricating qualities necessary to prevent dry eye.
   BULLET::::- "The metabolic activity of resting seeds increases as soon as they are hydrated during soaking. Complex biochemical changes occur during hydration and subsequent sprouting. The reserve chemical constituents, such as protein, starch and lipids, are broken down by enzymes into simple compounds that are used to make new compounds."
   A similar hypothesis suggests yawning is used for regulation of body temperature. Similarly, Guttmann and Dopart (2011) found, that, when a subject wearing earplugs yawned, a breeze is heard, caused by the flux of the air moving between the subject's ear and the environment. Guttmann and Dopart determined that a yawn causes one of three possible situations to occur: the brain cools down due to an influx or outflux of oxygen, the pressure in the brain is reduced by an outflux of oxygen, or the pressure of the brain is increased by an influx of air caused by increased cranial space.
   BULLET::::- Eating a Tear - Conan sometimes will say something that will cause him to shed, and then eat, a tear. This is pantomimed by running a finger from his eye down his cheek to his mouth.
   Lacrimal lake
  
  The lacrimal lake is the pool of tears in the lower conjunctival cul-de-sac, which drains into the opening of the tear drainage system (the "puncta lacrimalia"). The volume of the lacrimal lake has been estimated to be between 7 and 10 µL.
  
  Although the lacrimal lake usually contains 7–10 µL of tears, the maximum fluid it can usually hold is 25–30 µL before tearing occurs. Aging usually causes the eyelids to become more loose which in turn enables the lacrimal lake to hold even more fluid.
   The resolution stated that the operation of the resolution shall have no effect on rights, debts and claims existing with respect to funds prior to their transfer to the escrow account, and that the accounts from which such funds were transferred shall be kept open for retransfer of the funds in question. It also reiterated that the Compensation Commission and escrow account enjoy all privileges and rights of the United Nations, including immunity from legal proceedings.
  
  The resolution was approved by 14 votes to none, with one abstention from China.
   In April 2019, following the Trump administration not distributing money to West Bank and Gaza "because of perceived intransigence on peace talks by the Palestinians and payments to the families of those who have attacked Israelis", Merkley was one of six Democratic senators to introduce a resolution restoring US humanitarian aid to Palestinians in the West Bank and Gaza.
  
  BULLET::::- Saudi Arabia
   Each time the eyelids are closed through the action of the orbicularis, the medial palpebral ligament is tightened, the wall of the lacrimal sac is thus drawn lateralward and forward, so that a vacuum is made in it and the tears are sucked along the lacrimal canals into it. The lacrimal part of the orbicularis oculi draws the eyelids and the ends of the lacrimal canals medialward and compresses them against the surface of the globe of the eye, thus placing them in the most favorable situation for receiving the tears; it also compresses the lacrimal sac. This part comprises two pieces: Horner's muscle and the muscle of Riolan, the latter helps hold the eyelids together to keep the lacrimal passage waterproof.
   Lacritin stimulated secretion of tear proteins lipocalin and lactoferrin from monkey lacrimal acinar cells does not appear to be mediated by Ca, unlike the agonist carbachol. When monkey lacrimal acinar cells are stressed with inflammatory cytokines (as occurs in dry eye), carbachol loses its capacity to promote the secretion of lipocalin. However, lacritin stimulates lipocalin secretion even in the presence of stress.
  
  Section::::Distribution.
  
  Section::::Distribution.:Species.
   In contrast to the normal moisture of the eyes or even crying, there can be persistent dryness, scratching, and burning in the eyes, which are signs of dry eye syndrome (DES) or keratoconjunctivitis sicca (KCS). With this syndrome, the lacrimal glands produce less lacrimal fluid, which mainly occurs with ageing or certain medications. A thin strip of filter paper (placed at the edge of the eye) the Schirmer test, can be used to determine the level of dryness of the eye. Many medications or diseases that cause dry eye syndrome can also cause hyposalivation with xerostomia. Treatment varies according to aetiology and includes avoidance of exacerbating factors, tear stimulation and supplementation, increasing tear retention, eyelid cleansing, and treatment of eye inflammation.
   The proper fibers of the lips are oblique, and pass from the under surface of the skin to the mucous membrane, through the thickness of the lip.
   Section::::Causes.
  
  Any abnormality of any one of the three layers of tears produces an unstable tear film, resulting in symptoms of dry eyes.
  
  Section::::Causes.:Decreased tear or excessive evaporation.
   The iris contains two groups of smooth muscles; a circular group called the sphincter pupillae, and a radial group called the dilator pupillae. When the sphincter pupillae contract, the iris decreases or constricts the size of the pupil. The dilator pupillae, innervated by sympathetic nerves from the superior cervical ganglion, cause the pupil to dilate when they contract. These muscles are sometimes referred to as intrinsic eye muscles.
   In August 2014, Yawning Man returned to Europe with Arce, Mario Lalli and Stinson for a tour that ran from August 29 to September 7, after which they undertook the Legends of the Desert Tour with Fatso Jetson from February 2 to 28, 2015.
   BULLET::::- Darren is introduced to someone by his girlfriend, but somehow always says something innocent that upsets them. The girlfriend angrily "reminds" Darren that the person is recently bereaved and he had just made a reference to the departed. This is also promptly followed by Darren then upsetting somebody else, who attacks him without explanation.
  
  BULLET::::- Betty the Cleaner usually interrupts important events to ask when she can start cleaning, such as the evolution of apes and a UN meeting. her catchphrase is "Are youse gonna be long?" Played by Tim McGarry.
   Section::::Brain involvement.:Involuntary expiration.:Yawning.
   Excessive moisture as tears collected in the lacrimal sac travel down the nasolacrimal ducts where they drain into the inferior meatus in the nasal cavity.
  
  Section::::Structure.:Nose shape.
  
  The shape of the nose varies widely due to differences in the nasal bone shapes and formation of the bridge of the nose. Some nose shapes were classified for surgeries by Eden Warwick in "Nasology" 1848:
  
presuppositions: Everyone's eyes water after yawning. Humans eyes water after yawning.
corrections: Yawning does not cause eye watering for everyone. Not everyones eyes always water after yawning. 
raw_presuppositions: Everyone's eyes water after yawning. Humans eyes water after yawning. Your eyes always water after yawning.
raw_corrections: Yawning does not cause eye watering for everyone. Not everyones eyes always water after yawning.  Eyes don't always water after yawning, and this reaction doesn't happen to everyone.