Tear ducts and the Lacrimal System

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Lynx

Post   » Mon Nov 08, 2021 12:43 pm


I was looking around to see if I could find any kind of illustration of the nasolacrimal duct. At the moment, all I can find is one for a dog in the Merck manual (see illustrations, first one):
https://www.msdvetmanual.com/eye-diseas ... -apparatus
The tear production and drainage system is vital for health of the outer eye. Tear glands within the orbit (lacrimal and in some species Harder gland) as well as the superficial tear gland of the nictitating membrane (third eyelid) produce the collective preocular or precorneal tear film. This film consists of three layers: outer lipid (from the Meibomian glands), middle aqueous layer (from lacrimal and third eyelid glands), and deep layer (mucus) from the goblet cells within the conjunctiva.

The tear drainage system consists of two lacrimal puncta (except in the rabbit and pig, which have only one punctum), two canaliculi, the lacrimal sac (within the bony lacrimal fossa), and the long and often tortuous lacrimal duct (to empty tears within the forward nasal cavity).
And an article on how important lacrimal fluid is to the health of the eye. This gets very technical but the summary is informative.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3652637/

And a very accessible article on the lacrimal system in a human:
https://teachmeanatomy.info/head/organs ... mal-gland/

Perhaps not helpful for locating the duct but interesting nonetheless is this article, which touches on several species and regrets the lack of information on guinea pigs:
http://www.medirabbit.com/EN/Eye_diseas ... rabbit.pdf

This 2009 post on a UK forum notes that, "There is a test the vet can do to determine if the tear ducts are actually blocked - it involves putting fluorescene dye in the eye and monitoring it's appearance down the nostrils and in the throat"
https://www.theguineapigforum.co.uk/thr ... st-1329809

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