Free previewYou're reading the free part of this topic. The rest is included with Clinical.See what's included
Lacrimal system anatomy
Anatomy & Optics
Key Points
- •The lacrimal gland (surface ectoderm) has orbital and palpebral lobes separated by the levator aponeurosis; ~12 ductules drain through the palpebral lobe; parasympathetic secretomotor pathway: lacrimal nucleus → nervus intermedius → greater petrosal → pterygopalatine ganglion → lacrimal nerve → gland
- •The tear film is trilaminar: lipid (meibomian glands, prevents evaporation), aqueous (lacrimal + accessory glands, bulk volume), mucin (goblet cells MUC5AC + epithelial MUC1/4/16, enables wetting); TBUT >10 sec normal; Schirmer >15 mm normal
- •Lacrimal drainage: puncta (2) → canaliculi (~10 mm, 2mm vertical + 8mm horizontal) → common canaliculus → valve of Rosenmuller → lacrimal sac (12-15 mm, in lacrimal fossa between anterior and posterior lacrimal crests) → NLD (12-18 mm) → valve of Hasner → inferior meatus
- •CNLDO (imperforate valve of Hasner): ~5-6% of newborns symptomatic; 90-96% resolve by age 1; management: Crigler massage → probing (age 1-2) → intubation → DCR; never probe/irrigate during acute dacryocystitis
- •The lacrimal pump mechanism depends on Horner's muscle (deep pretarsal orbicularis heads) compressing the lacrimal sac during blinking; CN VII palsy → pump failure → epiphora even with patent drainage
Free preview ends here
Keep reading Lacrimal system anatomy
13 more sections are included with the Clinical plan.
- Definition
- Epidemiology
- Aetiology and causes
- Pathogenesis
- Classification
- Clinical features