It is said that there are three main types of tears. Not long ago I saw a series of patients with all three within hours of each other in the ER, and I thought there was a column in there.
Before breaking down this triumvirate of epiphoras, let’s take a quick look at the physiology of tears. We are traditionally taught that tears are produced by the lacrimal gland, but the truth is so much more complex.
Also in the tripartite organization, the tears consist of three layers – an outer lipid layer secreted by the gangster-sounding glands of Zeis and Moll in addition to the numerous Meibomian glands, a middle watery layer formed in the main lacrimal gland but with contributions from the more Germanic-sounding glands of Krause and Wolfring, and finally the inner mucous layer derived from the goblet cells, together with the crypts of Henle and the glands of Manz.
Who knows what they look like? All I know is that a deeply complex system of machines allows us to cry.
Of course, tears do a lot more. The first of the functions is the basal tear. This produces an even layer of tears that covers the cornea and has a myriad of responsibilities: keeping the cornea moist, allowing gas exchange, cleaning debris from the transparent surface, providing an immunological barrier, and maintaining a smooth optical surface for focusing. optimum point. Wonderful! We produce about a gram of these lube babies every day, which slows down as we get older.
Reflex tearing is the response to an irritant. Think of onions, whose infamy lies in their sulphurous nature, which when cut into pieces produce a nasty volatile cocktail of sulfenic acids and oxides. These trigger transient receptor potential channels in the ophthalmic nerve (V1), triggering tearing. The classic lesson is to keep your onions in the fridge until pruning to slow down the action of catalytic enzymes. Or you can just do like me and have someone else chop the onions. Bright lights and hot sensations on the tongue can do the same.
The emotional heartbreak is the weirdest. Humans are the only mammals to do this, and we cry, as you well know, in response to a plethora of powerful psychological stimuli (and the odd, well-choreographed TV commercial). Tears produced by emotion have a very different chemical composition from other tears and they are much more protein-rich. They look incredibly unique under an electron microscope.
When the tears are made, they collect in a glorious-named lacrimal lake, with a lacrimal papilla forming a small elevation at the edge of the lacrimal lake. The tears continue along the tributaries through the aqueducts. It all seems so bucolic, an emotional place, lined with weeping willows, even if they end up in the less gentrified nasal cavities.
Not too many emergency pathologies of the lacrimal apparatus that we face in emergencies, but we must know some of them:
- Nasal tear duct injury: Dog bites feature disproportionately. These are usually complex and almost universally require a referral to an ophthalmologist for repair to avoid a lifetime of universal crying.
- Dacryocystitis: result of obstruction of the lacrimo-nasal duct, with stagnant tears which become infected secondarily, forming an abscess which also requires surgical treatment (the misnamed dacryocystorhinostomy) as well as antibiotics.
- Sjögren’s syndrome: Chronic autoimmune disease attacking the secretory glands of the mouth and eyes. It is commonly associated with systemic sclerosis, systemic lupus erythematosus, or rheumatoid arthritis. Keratoconjunctival dryness can lead to significant corneal pathology, including ulcers.
Lachrymal pathology must be taken seriously because we can condemn our patients to a life of shortage or surplus in case of forgetfulness. We need optimally functioning tears for ocular longevity, even though the great 1980s UK band Tears for Fears would tell us: All for freedom and for fun / Nothing ever lasts forever / Everyone wants to rule the world.
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Dr Johnstonis a certified ER doctor, so the same as you but with a weird accent. She works at a trauma center in the old fashioned end of Perth, Western Australia. She is the author of the novel dust fall, available on his website, http://michellejohnston.com.au/. She is also a regular contributor to the Life in the Fast Lane blog athttps://lifeinthefastlane.com. Follow her on Twitter@Eleytheriusand read its past columns athttp://bit.ly/EMN-WhatLiesBeneath.