Lacrimal apparatus

Lacrimation, refers to non-emotional shedding of tears. 

The lacrimal apparatus is the physiological system containing the orbital structures for tear production and drainage.

The lacrimal apparatus consists of:  the lacrimal gland, which secretes the tears, and its excretory ducts, which convey the fluid to the surface of the human eye.

The lacrimal apparatus is a j-shaped serous gland located in lacrimal fossa:

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.

The innervation of the lacrimal apparatus involves both the a sympathetic supply through the carotid plexus of nerves around the internal carotid artery, and parasympathetically from the lacrimal nucleus of the facial nerve.

The blood supply to the lacrimal gland is provided by the ophthalmic artery with its branch the lacrimal artery.

The venous blood is drained from this region via the superior ophthalmic vein. 

The lacrimal system is made up of a secretory system, which produces tears, and an excretory system, which drains the tears. 

The lacrimal gland is produces emotional or reflexive tears. 

Some fluid of tears evaporate between blinks, and some is drained through the lacrimal punctum. 

Tears that are drained through the punctum will eventually be drained through the nose. 

Any excess fluid that did not go into the punctum will fall over the eyelid, which produces tears that are cried.

Crying or weeping is the dropping or welling of tears in the eyes in response to an emotional state, or pain. 

Emotions that can lead to crying include sadness, anger, and even happiness. 

Crying is a complex secretomotor phenomenon characterized by the shedding of tears from the lacrimal apparatus, without any irritation of the ocular structures.

Crying protects from conjunctivitis.

Various forms of crying are known as sobbing, weeping, wailing, whimpering, bawling, and blubbering.

A neuronal connection exists between the lacrimal gland and the areas of the human brain involved with emotion.

Tears made during emotional crying have a chemical composition which differs from other types of tears, with significantly greater quantities of the hormones prolactin, adrenocorticotropic hormone, and Leu-enkephalin, and the elements potassium and manganese.

Some evidence exists  that crying lowers stress levels, potentially due to the release of hormones such as oxytocin.

Crying May be an outlet or a result of a burst of intense emotional sensations, such as agony, surprise or joy. 

The remembrance of the positive aspects of crying, and may create an association between other positive events, such as resolving feelings of grief, reinforcing the idea that crying helped the individual.

Psychological theories of crying emphasize the relationship of crying to the experience of perceived helplessness.

Most animals can cry but only humans have psychoemotional shedding of tears (weeping).

Physical effects of crying: increased heart rate, sweating, and slowed breathing, and for some a calming effect.

Globus sensation is the most common side effect of crying, and refers to a feeling of a lump in the throat of the crier.

Globus sensation is a sympathetic nervous system response to the stress experienced.

The increased sympathetic nervous system response to crying is breathing, and includes expanding the glottis, which allows more air to pass through. 

Eventually the parasympathetic nervous system attempts to undo the sympathetic response by decreasing high stress activities and increasing recuperative processes  involving swallowing, a process which requires closing the fully expanded glottis to prevent food from entering the larynx. 

The attempt to close the glottis creates a sensation that feels like a lump in the individual’s throat.

Common side effects of crying are quivering lips, a runny nose, and an unsteady, cracking voice.

Studies on crying suggest: the average woman cries between 30 and 64 times a year, and the average man cries between 6 and 17 times a year; men tend to cry for between two and four minutes, and women cry for about six minutes. 

Crying turns into sobbing for women in 65% of cases, compared to just 6% for men. 

Before adolescence, there is no difference in crying between the sexes.

The gap between how often men and women cry is larger in wealthier, more democratic, and feminine countries.

Infants can shed tears at approximately 4–8 weeks of age.

The ability of a newborn to cry upon delivery signals they can successfully breathe on their own.

Three different types of cries are apparent in infants. 

Basic cry

Anger cry

Pain cry

Basic cry which is a systematic cry with a pattern of crying and silence. 

The basic cry starts with a cry, then a brief silence, which is followed by a short high-pitched inspiratory whistle. 

Then, there is a brief silence followed by another cry. 

Hunger is a main stimulant of the basic cry. 

An anger cry is much like the basic cry has more excess air that is forced through the vocal cords, making it a louder, more abrupt cry. 

Anger cry is characterized by the same temporal sequence as the basic pattern but is distinguished by differences in the length of the various phase components. 

The pain cry, which, has no preliminary moaning. 

The pain cry is one loud cry, followed by a period of breath holding.

Most people can determine whether an infant’s cry signifies anger or pain, and can distinguish their own infant’s cries than those of a different child.

There may be a correlation between the mother’s prenatal stress level and later amount of crying by the infant. 

She also found a correlation between birth trauma and crying.

Mothers who experience obstetrical interventions or who were made to feel powerless during birth have babies who cry more than other babies. 

Babies who had experience birth complications have longer crying spells at three months of age and awakened more frequently at night crying.

It has been proposed that a general emotional release occurs with infant crying when there is no obvious reason.

There are three types of tears: 

Basal, reflexive tears, and psychic tears. 

Basal tears are produced at a rate of about 1 to 2 microliters a minute, and are made in order to keep the eye lubricated and smooth out irregularities in the cornea. 

Reflexive tears are tears that are made in response to irritants to the eye, such as when chopping onions or getting poked in the eye. 

Psychic tears are produced by the lacrimal system and are the tears expelled during emotional states.

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