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Human tears. Tears are a clear liquid secreted by the lacrimal glands (tear gland) found in the eyes of all land mammals. [1] Tears are made up of water, electrolytes, proteins, lipids, and mucins that form layers on the surface of eyes. [2] The different types of tears—basal, reflex, and emotional—vary significantly in composition. [2]
Crying is the dropping of tears (or welling of tears in the eyes) in response to an emotional state or physical pain. Emotions that can lead to crying include sadness , anger , joy , and fear . Crying can also be caused by relief from a period of stress or anxiety , or as an empathetic response.
There are actually different types of tears. So what are they and why exactly do we cry? Experts explain.
Blinking provides moisture to the eye by irrigation using tears and a lubricant the eyes secrete. The eyelid provides suction across the eye from the tear duct to the entire eyeball to keep it from drying out. Closed eye of a human, displaying eyelashes which function to catch irritants when the eye is blinked.
The lacrimal gland is a compound tubuloacinar gland, it is made up of many lobules separated by connective tissue, each lobule contains many acini.The acini composed of large serous cells which, produce a watery serous secretion, serous cells are filled with lightly stained secretory granules and surrounded by well-developed myoepithelial cells and a sparse, vascular stroma.
Excess tears flow through the nasolacrimal duct which drains into the inferior nasal meatus. This is the reason the nose starts to run when a person is crying or has watery eyes from an allergy, and why one can sometimes taste eye drops. This is for the same reason when applying some eye drops it is often advised to close the nasolacrimal duct ...