Lacrimal Apparatus
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Direct answer
Tears are made in the lacrimal gland in the superolateral orbit, swept medially by blinking, and drained through a punctum on each lid margin into canaliculi, the lacrimal sac and the nasolacrimal duct, which opens into the inferior meatus of the nose below the inferior concha. The gland's secretomotor fibres travel a four-neuron pathway — greater petrosal nerve, nerve of the pterygoid canal, pterygopalatine ganglion, then the zygomatic and lacrimal nerves — which is why crying accompanies nasal secretion. Failure of drainage presents as epiphora, and failure of secretion as the dry eye of xerophthalmia, a deficiency strongly associated with vitamin A in Indian paediatric practice.
What you must remember
- The gland has a larger orbital part and a smaller palpebral part separated by the lateral expansion of the levator aponeurosis; only the palpebral part is visible on lid eversion.
- Secretomotor route: superior salivatory nucleus, greater petrosal nerve, nerve of the pterygoid canal, relay in the pterygopalatine ganglion, postganglionic fibres join the zygomatic nerve, cross to the lacrimal nerve and reach the gland.
- Each punctum lies at the medial end of a lid margin, turning into the lacrimal lake; the canaliculi (about 1 cm together) unite into the common canaliculus opening into the sac.
- The lacrimal sac sits in the lacrimal fossa between the anterior (frontal process of maxilla) and posterior (lacrimal bone) crests, crossed in front by the medial palpebral ligament.
- The nasolacrimal duct, about 18 mm long, runs down, slightly back and laterally in a bony canal to open under the inferior nasal concha; its lower end bears the valve of Hasner.
- Drainage is active: contraction of orbicularis oculi during blinking — the lacrimal pump — expands and compresses the sac, sucking tears in and expressing them down the duct.
- Tears drain ultimately into the inferior meatus, so the nose runs when the eye waters.
Working through epiphora in a child and in an adult
A three-month-old has constant watering of the left eye with sticky discharge since birth, but no redness of the eye itself. The anatomy localises the fault to the last millimetre of the system: the valve of Hasner fails to canalise at the lower end of the nasolacrimal duct, present in a proportion of newborns; most open spontaneously within the first year, and management per current ophthalmic practice is lacrimal sac massage with topical antibiotics initially, probing of the duct if symptoms persist beyond about a year, with intubation or dacryocystorhinostomy reserved for failures. A tense bluish swelling below the medial canthus at birth suggests a dacryocystocele rather than simple obstruction.
Contrast the adult with a swelling at the medial canthus below the medial palpebral ligament that fills and empties, with reflux of mucopus on pressure over the sac — a mucocele of the lacrimal sac from obstruction lower in the duct. The surgical answer is anatomical: a dacryocystorhinostomy opens a new drainage window from the sac into the middle meatus of the nose through the nasal bone, bypassing the duct entirely. Above the medial palpebral ligament, however, a sac-region swelling is suspect, as the fascial arrangement directs sac distension downward — swellings above it must be imaged for tumour before surgery is planned.
Where students slip
The secretomotor pathway is the commonest casualty. Candidates route the parasympathetic supply "with the lacrimal nerve from the start"; the fibres actually arise from the greater petrosal nerve of the facial nerve, relay in the pterygopalatine ganglion, and only join orbital nerves via the zygomatic branch of V2 crossing to the lacrimal nerve of V1 — four named stations examiners demand in order. Second, the opening of the nasolacrimal duct is placed "in the middle meatus"; it opens into the inferior meatus under the inferior concha, and the middle meatus drains the paranasal sinuses — mixing the two is a cardinal error. Third, remember that the sac's fossa straddles two bones; the anterior lacrimal crest belongs to the maxilla and the posterior to the lacrimal bone, the suture between them being the osteotomy landmark for sac surgery.
Frequently asked questions
Where does the nasolacrimal duct open?
Into the inferior meatus of the nose beneath the inferior concha, its opening guarded by the valve of Hasner.
Trace the secretomotor pathway to the lacrimal gland.
Greater petrosal nerve from the facial nerve, through the nerve of the pterygoid canal, relay in the pterygopalatine ganglion, then via the zygomatic nerve to the lacrimal nerve and gland.
Why is tear drainage called an active pump?
Blinking contracts orbicularis oculi around the canaliculi and sac — the lacrimal pump of Horner's muscle — drawing tears in and expressing them downwards.
What is the landmark between the lacrimal sac and the duct?
The medial palpebral ligament crosses the sac; swellings below it point to sac distension, while those above it warrant imaging for tumour.
Why does the nose run when we cry?
Excess tears overflow through the puncta, canaliculi, sac and nasolacrimal duct into the inferior meatus, mixing with nasal secretion.