Ampulla of lacrimal canaliculus

At a glance

English

Ampulla of lacrimal canaliculus

Latin (TA2)

Ampulla canaliculi lacrimalis

System

Eye

Region

Head

Side

Paired, left and right

About the ampulla of lacrimal canaliculus

Each eyelid has one lacrimal canaliculus, a fine channel that carries tears from the punctum at the inner end of the lid margin towards the lacrimal sac. The canaliculus does not run straight. It first passes roughly at right angles to the lid margin for about two millimetres, upwards in the upper lid and downwards in the lower lid, and then turns sharply to run horizontally towards the nose. The ampulla is the slight widening found exactly at this corner.

The ampulla sits within the medial part of the eyelid, just beyond the lacrimal papilla, the small raised mound that carries the punctum. Around it lie fibres of the lacrimal part of orbicularis oculi, the slip of the muscle that passes behind the lacrimal sac to the posterior lacrimal crest. Its lining matches the rest of the canaliculus: non-keratinised stratified squamous epithelium on an elastic layer that lets the passage stretch.

Its role is mechanical. With each blink the surrounding muscle squeezes the vertical limb and shortens the canaliculus, pushing tear fluid on towards the sac; as the lids open, the passage recoils and draws fresh fluid in from the lacrimal lake. The dilated bend is thought to act as a small reservoir in this pumping cycle.

The shape matters when clinicians probe or irrigate the tear passages. A probe is introduced vertically through the punctum, then turned horizontal at the level of the ampulla while the lid is pulled outwards to straighten the channel; forcing it straight ahead risks making a false passage. Inflammation of the canaliculus (canaliculitis), often with small stones (concretions) in the canaliculus, can cause a red, pouting punctum and watering.

Function and supply

Begins at

Continues from the short vertical limb of the canaliculus that begins at the lacrimal punctum.

Ends at

Leads into the horizontal limb of the canaliculus, which runs medially to the lacrimal sac, usually through a common canaliculus.

Function

Acts as a small reservoir at the bend of the canaliculus during the blink-driven pumping of tears.

Nerve supply

Sensory fibres from the infratrochlear nerve; the surrounding orbicularis oculi fibres are supplied by the facial nerve.

Blood supply

Branches of the medial palpebral arteries from the ophthalmic artery.