Tears
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Tears are commonly associated with crying |
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.
In humans, the tear film coating the eye has three distinct layers:# 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
hydrophobic layer that allows for even distribution of the aqueous layer.# The
aqueous layer contains
water and other substances such as proteins (e.g. tear lipocalin, lactoferrin and lysozyme[
1]) secreted by the glands of Kraus and Wolfring and the
lacrimal gland.# 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.
One lacrimal gland is located above and beside each eye, behind the upper
eyelid. The lacrimal glands secrete lacrimal fluid which flows through lacrimal 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, then flows via the
puncta 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.
There are three basic types of tears:#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.#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. These
reflex tears attempt to wash out irritants that may have come into contact with the eye.#Crying or weeping: The third category, generally referred to as
crying or
weeping, is increased lacrimation due to strong
emotional stress or physical pain. This practice is not restricted to negative emotions; many people have been known to cry when extremely happy. 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.
"
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 [
2].
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 in fact a response to irritation caused by the original tear film deficiency.
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.
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,
humor, or other strongly-experienced emotions.
In many cultures, crying is associated with babies and children. Some cultures consider crying to be undignified and infantile, casting aspersion on those who cry publicly. In most western cultures, it is more socially acceptable for women to cry in public than men, but this is certainly not true for all human cultures.
An insincere display of grief or dishonest remorse is called
crocodile tears, from the ancient anecdote that
crocodiles would
pretend to weep in order to lure prey [
3].
Many religions describe
gods or
prophets as crying:
*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 the
Bible (in the
King James Version of the Bible and some other
English translations) is simply:
"Jesus wept."*
Jade is sometimes known as "tears of the
Buddha".
*The
Incas referred to silver as the "tears of the moon".
The
Gift of Tears in Shin Buddhism:
Tears of joy and grief cleanse our souls. Christians as well may perceive tears as 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 Easten Christian Traditions.
Tears play an important role in the Eastern Christian Mystic Theology.
Scienceiq.com[
4]
*
Nasolacrimal System Anatomy - eMedicine.com*The Spiritual Context of Tears -
The Gift of Tears
