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Asked by Ciara Shannon to Colin, John, Kevin, Shikha, Triona on 17 Nov 2014.
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Tríona O'Connell answered on 17 Nov 2014:
Glands in your eyes,just above your nose (there’s a tunnel running between these andyour nose, so if you’re crying your nose runs (and if you have a bad bad cold you can bubble snot up out your tear duct)).
There’s more than just salt and water in them though. They have some oils to make sure your eyes don’t dry out (oil is much better at that than water). They also have an enzyme called lysozyme in them which breaks open bacteria to reduce the chances of getting an infection. (we do experiments with our students about extracting lysozyme from egg whites, and we have a way for testing lysozyme activity. Apparenlty I’m not allowed to make the students cry to find out how much lysozyme activity is in their tears though 🙁 )
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Shikha Sharma answered on 17 Nov 2014:
Hi Ciara,
All tears come from a tear gland known as lacrimal gland. It is a small almond-shaped structure which is located just above the upper, outer corner of the eye. It secretes lacrimal fluid, which enters into the space between the eyeball and lids. The blinking of eyes, help in spreading the lacrimal fluid across the surface of the eye. Even if you’re asleep, tears are still being produced.
There are different types of tears and even their composition varies as well. For example if something gets in your eye and irritates it, your tear glands make more tears to try and flush the irritant away. These are reflex tears. If something makes you sad or extra happy, your tear glands produce emotional tears. Generally, tears are composed of water, salts, antibodies and lysozymes (antibacterial enzymes) whereas emotional tears are made up of more protein-based hormones, such as prolactin, adrenocorticotropic, and leucine enkephalin (a natural pain killer).
When we produce lots of tears, they can’t all drain into our nasal cavity, so they overflow and run down your cheeks.
So, sometimes crying is good to clean your eyes 😀 😀
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