FACTOID # 8: Bookworms: Vermont has the highest number of high school teachers per capita and third highest number of librarians per capita.
 
 Home   Encyclopedia   Statistics   States A-Z   Flags   Maps   FAQ   About 
   
 
WHAT'S NEW
RELATED ARTICLES
People who viewed "Tears" also viewed:
 

SEARCH ALL

FACTS & STATISTICS    Advanced view

Search encyclopedia, statistics and forums:

 

 

(* = Graphable)

 

 


Encyclopedia > Tears
The tear system. A) Tear gland / Lacrimal gland B) Superior lacrimal punctum C) Superior lacrimal canal D) Tear sac / Lacrimal sac E) Inferior lacrimal punctum F) Inferior lacrimal canal G) Nasolacrimal canal
The tear system. A) Tear gland / Lacrimal gland B) Superior lacrimal punctum C) Superior lacrimal canal D) Tear sac / Lacrimal sac E) Inferior lacrimal punctum F) Inferior lacrimal canal G) Nasolacrimal canal

Tears are a liquid produced by the body's process of lacrimation to clean and lubricate the eyes. The word lacrimation may also be used in a medical or literary sense to refer to crying. Image File history File links Tear_system. ... Image File history File links Tear_system. ... A human eye Eyes are organs of vision that detect light. ...

Contents

Physiology

In humans, the tear film coating the eye has three distinct layers, from the most outer surface:

  1. The lipid layer contains oils secreted by the meibomian glands. The outer-most layer of the tear film, it coats the aqueous layer to provide a hydrophobic barrier that retards evaporation and prevents tears spilling onto the cheek.
  2. The aqueous layer contains water and other substances such as proteins (e.g. tear lipocalin, lactoferrin, lysozyme[1] and lacritin) secreted by the glands and the lacrimal gland. The aqueous layer serves to promote spreading of the tear film, control of infectious agents and osmotic regulation.
  3. The mucous layer contains mucin secreted by the conjunctival goblet cells. The inner-most layer of the tear film, it coats the cornea to provide a hydrophilic layer that allows for even distribution of the tear film, as well as mucus covering of the cornea.

Having a thin tear film may prevent you from wearing contact lenses as the amount of oxygen need is higher than normal and contact lenses stop oxygen entering your eye. You will find that your eyes will dry out while wearing contact lenses whilst having a thin tear film. Special eye drops are available for contact lense wearers, also certain types of contact lenses are designed to let more oxygen through. A polyunsaturated triglyceride. ... The Meibomian glands (or tarsal glands) are a special kind of sebaceous glands at the rim of the eyelids, responsible for the supply of sebum, an oily substance that prevents evaporation of the eyes tear film. ... In chemistry, hydrophobic or lipophilic species, or hydrophobes, tend to be electrically neutral and nonpolar, and thus prefer other neutral and nonpolar solvents or molecular environments. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... Lactoferrin is a globular protein found in milk and many mucosal secretions such as tears. ... Lacritin is a common glycoprotein of the human tear film. ... The lacrimal glands are paired glands, one for each eye, that secrete the aqueous layer of the tear film. ... Mucins are a family of large, heavily glycosylated proteins. ... Goblet cells are glandular epithelial cells that are specifically designed to secrete mucus. ... The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber, providing most of an eyes optical power [1]. Together with the lens, the cornea refracts light and, as a result, helps the eye to focus. ... The adjective hydrophilic describes something that likes water (from Greek hydros = water; philos = friend). ... A soft contact lens A contact lens (also known as contact, for short) is a corrective or cosmetic lens placed on the cornea of the eye atop the iris. ... General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Standard atomic weight 15. ... Eye Drops was a television program on TechTV that showcased short computer animation movies and clips made using off the shelf 3D animation software. ...


Drainage of tear film

One lacrimal gland is located superiortemporally to each eye, behind the upper eyelid. The lacrimal glands secrete lacrimal fluid which flows through the main excretory ducts into the space between the eyeball and lids. When the eyes blink the lacrimal fluid is spread across the surface of the eye. Lacrimal fluid gathers in the lacrimal lake, and is drawn into the puncta by capillary action, then flows through the lacrimal canaliculi at the inner corner of the eyelids through the nasolacrimal duct, and finally into the nasal cavity. An excess of tears, as with strong emotion, can thus cause the nose to run. An eyelid is a thin fold of skin and muscle that covers and protects an eye. ... The lacrimal lake (lacus lacrimalis) is the pool of tears in the lower conjunctival cul-de-sac, which drains into the opening of the tear drainage system (i. ... The lacrimal canaliculi, one in each eyelid, commence at minute orifices, termed puncta lacrimalia (or lacrimal punctum, or lacrimal point), on the summits of the papillae lacrimales, seen on the margins of the lids at the lateral extremity of the lacus lacrimalis. ... The lacrimal canaliculi, also known as the lacrimal canals or lacrimal ducts, are the small channels in each eyelid that commence at minute orifices, termed puncta lacrimalia, on the summits of the papillæ lacrimales, seen on the margins of the lids at the lateral extremity of the lacus lacrimalis. ... The nasolacrimal duct carries tears from the lacrimal sac into the nasal cavity. ... The nasal cavity (or nasal fossa) is a large air-filled space above and behind the nose in the middle of the face. ... Emotional redirects here. ...


Types of tears

There are three very basic types of tears:

  1. Basal tears: In healthy mammalian eyes, the cornea is continually kept wet and nourished by basal tears. They lubricate the eye and help to keep it clear of dust. Tear fluid contains water, mucin, lipids, lysozyme, lactoferrin, lipocalin, lacritin, immunoglobulins, glucose, urea, sodium, and potassium. Some of the substances in lacrimal fluid fight against bacterial infection as a part of the immune system.
  2. Reflex tears: The second type of tears results from irritation of the eye by foreign particles, or from the presence of irritant substances such as onion vapors, tear gas or pepper spray in the eye's environment. These reflex tears attempt to wash out irritants that may have come into contact with the eye.
  3. Crying or weeping (psychic tears): The third category, generally referred to as crying or weeping, is increased lacrimation due to strong emotional stress, depression or physical pain. This practice is not restricted to negative emotions; many people have been known to cry when extremely happy or when they are laughing. In humans, emotional tears can be accompanied by reddening of the face and sobbing — cough-like, convulsive breathing, sometimes involving spasms of the whole upper body. Tears brought about by emotions have a different chemical make up than those for lubrication. The limbic system is involved in production of basic emotional drives, such as anger, fear, etc. The limbic system, specifically the hypothalamus, also has a degree of control over the autonomic system. The parasympathetic branch of the autonomic system controls the lacrimal glands via the neurotransmitter acetylcholine through both the nicotinic and muscarinic receptors. When these receptors are activated that the lacrimal gland is stimulated to produce tears.[2]

Subclasses & Infraclasses Subclass †Allotheria* Subclass Prototheria Subclass Theria Infraclass †Trituberculata Infraclass Metatheria Infraclass Eutheria Mammals (class Mammalia) are warm-blooded, vertebrate animals characterized by the production of milk in female mammary glands and by the presence of: hair, three middle ear bones used in hearing, and a neocortex region in... The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber, providing most of an eyes optical power [1]. Together with the lens, the cornea refracts light and, as a result, helps the eye to focus. ... Look up dust in Wiktionary, the free dictionary. ... Mucins are a family of large, heavily glycosylated proteins. ... Figure 1: Basic lipid structure. ... Lysozyme single crystal. ... Lactoferrin is a globular protein found in milk and many mucosal secretions such as tears. ... The lipocalin family of proteins is a functionally and structurally diverse group. ... Lacritin is a common glycoprotein of the human tear film. ... Schematic of antibody binding to an antigen An antibody is a protein complex used by the immune system to identify and neutralize foreign objects like bacteria and viruses. ... Glucose (Glc), a monosaccharide (or simple sugar), is the most important carbohydrate in biology. ... Urea is an organic compound with the chemical formula (NH2)2CO. Urea is also known as carbamide, especially in the recommended International Nonproprietary Names (rINN) in use in Europe. ... General Name, Symbol, Number sodium, Na, 11 Chemical series alkali metals Group, Period, Block 1, 3, s Appearance silvery white Standard atomic weight 22. ... General Name, Symbol, Number potassium, K, 19 Chemical series alkali metals Group, Period, Block 1, 4, s Appearance silvery white Standard atomic weight 39. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... An infection is the detrimental colonization of a host organism by a foreign species. ... A scanning electron microscope image of a single neutrophil (yellow), engulfing anthrax bacteria (orange). ... Binomial name L. Many plants in the genus Allium are known by the common name onion but, used without qualifiers, it usually refers to Allium cepa. ... A riot control agent is a type of lachrymatory agent (or lacrimatory agent). ... Pepper spray (also known as OC spray (from Oleoresin Capsicum), OC gas, capsicum spray, or oleoresin capsicum) is a lachrymatory agent (a chemical compound that irritates the eyes to cause tears, pain, and even temporary blindness) that is used in riot control, crowd control and personal self-defense, including defense... Stress (roughly the opposite of relaxation) is a medical term for a wide range of strong external stimuli, both physiological and psychological, which can cause a physiological response called the general adaptation syndrome, first described in 1936 by Hans Selye in the journal Nature. ... “Sad” redirects here. ... “Hurting” redirects here. ... The limbic system (Latin limbus: border or edge) includes the structures in the human brain involved in emotion, motivation, and emotional association with memory. ... The chemical compound acetylcholine, often abbreviated as ACh, was the first neurotransmitter to be identified. ... Nicotinic Receptors form ion channels present in the plasma membrane of cells. ... Muscarinic receptors are those membrane bound acetylcholine receptors that are more sensitive to muscarine than to nicotine. ...

Diseases and disorders

Quality of vision is affected by the stability of the tear film.[3] This is a partial list of human eye diseases and disorders. ...


"Crocodile tears syndrome" is an uncommon consequence of recovery from Bell's palsy where faulty regeneration of the facial nerve causes sufferers to shed tears while eating.[4] Bells palsy (or facial palsy) is characterised by facial drooping on the affected half, due to malfunction of the facial nerve (VII cranial nerve), which controls the muscles of the face. ... The facial nerve is the seventh (VII) of twelve paired cranial nerves. ...


Keratoconjunctivitis sicca, more commonly known as dry eye, is a very common disorder of the tear film. Paradoxically, sufferers can experience watering of the eyes which is Keratoconjunctivitis sicca (KCS), also called keratitis sicca,[1] sicca syndrome,[1] xerophthalmia,[1] dry eye syndrome (DES),[1] or simply dry eyes,[1] is an eye disease caused by decreased tear production or increased tear film evaporation commonly found in humans and some animals[2]. Keratoconjunctivitis sicca is Latin and...


"Leamy Eye" is a condition whereby there is excessive watering of one eye in response to environmental stimuli.


Societal aspects

A Frenchman weeps as French battle standards are evacuated by sea out of reach of the German invaders in 1940.
A Frenchman weeps as French battle standards are evacuated by sea out of reach of the German invaders in 1940.

Most mammals will produce tears in response to extreme pain or other stimuli, but crying as an emotional reaction is considered by many to be a uniquely human phenomenon, possibly due to humans' advanced self-awareness. Some studies suggest that elephants and gorillas may cry as well.[5] Image File history File links Size of this preview: 745 × 600 pixelsFull resolution (2648 × 2131 pixel, file size: 831 KB, MIME type: image/jpeg) Description: A Frenchman weeps as German soldiers march into the French capital, Paris, on June 14, 1940, after the Allied armies had been driven back across... Image File history File links Size of this preview: 745 × 600 pixelsFull resolution (2648 × 2131 pixel, file size: 831 KB, MIME type: image/jpeg) Description: A Frenchman weeps as German soldiers march into the French capital, Paris, on June 14, 1940, after the Allied armies had been driven back across... “Hurting” redirects here. ... Emotional redirects here. ... This article is about modern humans. ... It has been suggested that this article or section be merged with Self-consciousness. ... Genera and Species Loxodonta Loxodonta cyclotis Loxodonta africana Elephas Elephas maximus Elephas antiquus † Elephas beyeri † Elephas celebensis † Elephas cypriotes † Elephas ekorensis † Elephas falconeri † Elephas iolensis † Elephas planifrons † Elephas platycephalus † Elephas recki † Stegodon † Mammuthus † Elephantidae (the elephants) is a family of pachyderm, and the only remaining family in the order Proboscidea... Type species Troglodytes gorilla Savage, 1847 distribution of Gorilla Species Gorilla gorilla Gorilla beringei The gorilla, the largest of the living primates, is a ground-dwelling omnivore that inhabits the forests of Africa. ...


In nearly all cultures, crying is seen as a specific act associated with tears trickling down the cheeks and accompanied by characteristic sobbing sounds. Emotional triggers are most often anger and grief, but crying can also be triggered by sadness, joy, fear, laughter or humor, frustration, or other strongly-experienced emotions. Sound is a disturbance of mechanical energy that propagates through matter as a wave. ... Anger may be a (physiological and psychological) response to a perceived threat to self or important others, present, past, or future. ... It has been suggested that Anticipatory Grief be merged into this article or section. ... In everyday language depression refers to any downturn in mood, which may be relatively transitory and perhaps due to something trivial. ... “Happy” redirects here. ... Fear is an emotional response to impending danger, that is tied to anxiety. ... Happy Tree Friends character, see Giggles (Happy Tree Friends). ... Look up Humour in Wiktionary, the free dictionary. ... This article does not cite any references or sources. ...


In many cultures, crying is associated with babies and children. Some cultures consider crying to be undignified and infantile, casting aspersions on those who cry publicly, except if it is due to the death of a close friend or relative. In most cultures, it is more socially acceptable for women to cry than men.


An insincere display of grief or dishonest remorse is called crocodile tears, from the ancient anecdote that crocodiles would pretend to weep while luring or devouring their prey.[6] Crocodile tears is the false or insincere weeping, a hypocritical display of emotions. ... An anecdote is a short tale narrating an interesting or amusing biographical incident. ... Genera Mecistops Crocodylus Osteolaemus See full taxonomy. ...


Spiritual aspects

Many religions describe gods or prophets as crying: This article discusses the term God in the context of monotheism and henotheism. ... In religion, a prophet (or prophetess) is a person who has directly encountered the numinous or the divine and serves as an intermediary with humanity. ...

  • According to a hadith, the prophet Muhammad proclaimed: "This (tears) is an expression of the tenderness and compassion, which the Lord hath put into the hearts of His servants. The Lord doth not have compassion on and commiserate with His servants, except such as are tender and full of feeling."
  • The shortest verse in English translated Bibles is found in the Gospel of John 11:35, "Jesus wept."
  • Jade is sometimes known as "tears of the Buddha".

The Gift of Tears in Shin Buddhism: Tears of joy and grief cleanse our souls. Christians as well may perceive tears as a spiritual gift when they refer to Gospel of Jesus Christ: "Blessed are you that weep now, for you shall laugh" (Luke 6.21), while Weeping Icons are a common feature of the Eastern Christian Traditions. This article or section does not cite any references or sources. ... Muhammad in a new genre of Islamic calligraphy started in the 17th century by Hafiz Osman. ... This Gutenberg Bible is displayed by the United States Library. ... Jesus wept (Greek: ἐδάκρυσεν ὁ ἰησοῦς; Vulgate: Et lacrimatus est Iesus) is a phrase famous for being the shortest verse in the Christian New Testament according to the division of chapters and verses of the Bible. ... A selection of antique, hand-crafted Chinese jade (jadeite) buttons Unworked Jade Jade is used as an ornamental stone, the term jade is applied to two different rocks that are made up of different silicate minerals. ... Media:Example. ...


References

  1. ^ http://www.medrounds.org/ocular-pathology-study-guide/2005/10/tear-proteins.html
  2. ^ Skorucak A. "The Science of Tears." ScienceIQ.com. Accessed September 29, 2006.
  3. ^ Szczesna DH, Jaronski J, Kasprzak HT, Stenevi U. "Interferometric measurements of dynamic changes of tear film." J Biomed Opt. 2006 May-Jun;11(3):34028. PMID 16822077.
  4. ^ http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2261223&dopt=Abstract
  5. ^ Masson, Jeffrey Moussaieff, McCarthy, Susan, When Elephants Weep, Delta 1996 isbn: 978-0385314282
  6. ^ http://www.worldwidewords.org/qa/qa-cro1.htm

External links

  • Nasolacrimal System Anatomy - eMedicine.com
  • The Spiritual Context of Tears - The Gift of Tears

  Results from FactBites:
 
Tears - Wikipedia, the free encyclopedia (884 words)
Tears are a liquid produced by the body's process of lacrimation to clean and lubricate the eyes.
Reflex tears: The second type of tears results from irritation to the eye by foreign particles, or substances such as onion vapors or tear gas or pepper spray.
Jade is sometimes known as "tears of the Buddha".
Tears (4265 words)
If tears and sweat in humans are claimed to be due to an aquatic lifestyle and the need to excrete salt, the aquatic lifestyle must have been in a salt water environment.
Morgan has suggested that the source of control for psychogenic tearing is important to her theory, but this is based on her mistaken idea that human emotional tearing is a characteristic shared by aquatic animals and no other animals.
The idea that human tears indicate a marine past is certainly far less parsimonious than the idea that the actual observed and measured active secretion of the lacrimal gland indicates our actual environmental past habitat would be terrestrial rather than aquatic.
  More results at FactBites »

 
 

COMMENTARY     


Share your thoughts, questions and commentary here
Your name
Your comments

Want to know more?
Search encyclopedia, statistics and forums:

 


Press Releases |  Feeds | Contact
The Wikipedia article included on this page is licensed under the GFDL.
Images may be subject to relevant owners' copyright.
All other elements are (c) copyright NationMaster.com 2003-5. All Rights Reserved.
Usage implies agreement with terms, 1022, m