Lacrimal and Nasolacrimal ducts

Question 1

Precorneal tear film

Answer 1

trilaminar structure: mucin, lipid, aqueous

>7-10 um

basal and reflex pdn

Question 2

mucin layer

Answer 2

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

Question 3

aqueous portion of tears

Answer 3

most plentiful

middle

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

Question 4

lipid layer of tears

Answer 4

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

Question 5

nasolacrimal system

Answer 5

allows tears to be removed from ocular surface

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

Question 6

third eyelid

Answer 6

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