Lacrimal and Nasolacrimal ducts Flashcards Preview

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Flashcards in Lacrimal and Nasolacrimal ducts Deck (6)
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Precorneal tear film

trilaminar structure: mucin, lipid, aqueous

>7-10 um

basal and reflex pdn


mucin layer

innermost portion of tears

>0.1 um

produced by conjunctival goblet cells-ventral conjunctival fornix

functions: adhere tears to cornea, maintain tear film stability, maintains optically smooth surface, binds particular matter in tears


aqueous portion of tears

most plentiful


produced by orbital lacrimal gland & gland of the third eyelid

components: lysozyme, electrolytes, alb, glob, glu, lactoferrin

functions: corneal lubrication, corneal nutrition, oxygenation, removal of particular matter and metabolic by products, antibacterial


lipid layer of tears

outermost layer

~0.01-0.05 um thick

produced by Meiobomian glands

liquid at body temp

functions: reduce evaporation of tears, allows smooth, even spread of tears across cornea


nasolacrimal system

allows tears to be removed from ocular surface

components: eyelid puncta, nasolacrimal canaliculi, lacrimal sac, nasolacrimal duct, nasal puncta


third eyelid

aka nictitans or nictitating membrane

movement from ventromedial to dorsolateral

spreads tears, physical protection to globe, passive motion-when globe retracted

lined by conjunctiva

T-shaped cartilage

gland located at base of third eyelid, bulbar surface

lymphoid follicles on bulbar surface