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Nasolacrimal Duct
Nervous System

Nasolacrimal Duct

Ductus nasolacrimalis

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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.

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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.

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Nasolacrimal Duct

ScienceDirect image

Nasolacrimal duct development begins as a thickening of the ectoderm that becomes buried in the mesoderm of the nasal pits between the lateral nasal prominence and the maxillary process.

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