Quick Facts
The lacrimal canaliculus is the short passage in an eyelid, beginning at the punctum, that leads from the lacrimal lake to the lacrimal sac (Dorland, 2011).
Related parts of the anatomy
Structure and/or Key Feature(s)
Lacrimal canaliculi are small drainage channels from each eyelid that collect tears. They are found just adjacent to the medial angle of the eye. Tears collect here and pass through a punctum to enter either the superior or inferior lacrimal canaliculus. Each canaliculus is initially vertical as it travels medially from its punctum. It then widens forming an ampulla and passes towards the lacrimal sac. The superior and inferior canaliculi unite forming a common lacrimal canaliculus, which drains into the lacrimal sac (Standring, 2016).
Anatomical Relations
The orbicularis oculi muscle fibers interweave between the lacrimal canaliculi forming a “sphincter-like” arrangement that can facilitate tear drainage.
Function
The lacrimal canaliculi are responsible for draining tears from the medial angle of the eye. Each tear drop consists of about 7 μl of fluid. Some of the tear fluid is lost to evaporation or absorption into the conjunctiva; however, the majority is drained via the nasolacrimal drainage system. Tears collect at the medial angle of the eye (medial canthus) and by way of the puncta drain into the superior and inferior lacrimal canaliculi. These transport the tears to the lacrimal sac, and then into the nasolacrimal duct that directs the tears to the nasal cavity.
References
Dorland, W. (2011) Dorland's Illustrated Medical Dictionary. 32nd edn. Philadelphia, USA: Elsevier Saunders.
Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41 edn.: Elsevier Limited.
