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.
Physiology
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*) 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.
Baby Crying Excessively - Guide for parents by a family doctor.
Meta Description: [ A grizzly baby can be extremely stressful for parents. This article looks at possible causes of crying in infants, and when to seek help..., Medic8 Family Health Guide - your trusted source for health information online. More than 500 health-related articles written by qualified health profession... ]
Dealing with Crybabies - Parental advice from an experienced parent.
Meta Description: [ The Light Keeper is dedicated to all who keep the light at home as a stay at home or work at home parent ]