Structure
The nasolacrimal duct forms the inferior continuation of the lacrimal sac. It is approximately 18mm long and descends to open anteriorly in the inferior meatus of the nasal cavity. A fold of mucosa, the plica lacrimalis, extends over the opening of the nasolacrimal duct in the nasal cavity (ostium lacrimalis) forming a valve.
Related parts of the anatomy
Key Features & Anatomical Relations
The nasolacrimal duct is contained within an osseous canal formed by the lacrimal bone, maxilla, and inferior nasal concha.
Function
The nasolacrimal duct aids in draining tears from the medial angle of the eye. Each tear drop consists of about 7μl of fluid. The tear is distributed over the cornea (1-2μl) and along the upper and lower margins of the eyelids (Standring, 2016). 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 two puncta in the region drain it into the superior and inferior lacrimal canaliculi. The canaliculi transport the tears to the lacrimal sac, and then onto the nasolacrimal duct which directs the tears to the inferior meatus of the nasal cavity.
References
Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series: Elsevier Limited.
Learn more about this topic from other Elsevier products
Nasolacrimal Duct
A dacryocystocele or dacryocele is a fluid collection in the nasolacrimal duct caused by blockage of the proximal or distal portions of the duct.
