|  | | - Lacrimal Gland
- separated from orbit by fibroadipose tissue
- divided by LPS aponeurosis, smaller palpebral portion visible, larger orbital half hidden
- blood vessels, lymph, nerve, and excretory ducts pass from orbital part through palpebral section
- don’t biopsy or remove palpebral lobe which might significantly reduce tearing
- ducts empty 5mm above superior tarsal border
- reflex tear arc: afferent from V stimulates tear production from lacrimal gland; efferent complicated (with parasympathetics from VII, sympathetics not understood)
- exocrine gland, acinar and myoepithelial cells, lacrimal artery
- Accessory Glands of Krause and Wolfring
- no neural control, basal tear production (BST)
- located in sup fornix & above sup border of tarsus
- Canalicular System
- puncta sit in tear lake, approx 6mm from canthus, then 2 mm ampulla, then canaliculi extend medially 8-10 mm to common canaliculus (in 90% of population), then to lat wall of tear sac
- dilation prior to sac: sinus of Maier, enters sac superior and posterior
- valve of Rosenmuller prevents reflux from sac into common canaliculus during tear pump
- sac lies btw ant and post crura of med canthal tendon in lacrimal sac fossa
- puncta/lids move medially with lid closure
- deep heads of preseptal orbicularis (Horner’s muscle) inserts on post lacrimal crest, lateral half of superior lacrimal sac, encircles canaliculi to help pump
- Bony System
- interosseos direction of Nasolacrimal Duct = inferior and slightly. lateral, posterior
- Nasolacrimal Duct is approx 12 mm long, intranasal ostium high up in inf turbinate, covered by valve of Hasner, approx 2.5 cm post to naris on lat wall
- lacrimal bone very thin, therefore aim posteriorly in DCR
- ethmoid air cells are at superior and deeper parts of fossa, but may extend under entire fossa
- mucosa of ethmoid cells gray, thin, and friable
- Lacrimal Pump Model
- orbicularis actively pumps tears from lake
- Rosengren-Doane model: orb m contraction > + pressure in lacrimal sac > tears forced into nose > lids open, move laterally > - pressure in sac helped by closed valve of Hasner > lids open fully and puncta pop open, with - pressure drawing tears into ampulla and canaliculi
- Jones model: closure--lateral move = negative pressure
- Becker model: closure--upper half lateral move = lower pressure, lower half medial move with higher pressure
- fistulas develop inferior to medial canthal tendon b/c tendon itself is tough
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Visit Quest Medical / LacriCATH website to learn more
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