Surf Wiki
Save to docs
science/biology

From Surf Wiki (app.surf) — the open knowledge base

Nasolacrimal duct

Carries tears from the lacrimal sac of the eye into the nasal cavity

Summary

Carries tears from the lacrimal sac of the eye into the nasal cavity

FieldValue
NameNasolacrimal duct
Latinductus nasolacrimalis
ImageGray896.png
CaptionThe lacrimal apparatus. Right side.

The nasolacrimal duct (also called the tear duct) carries tears from the lacrimal sac of the eye into the nasal cavity. The duct begins in the eye socket between the maxillary and lacrimal bones, from where it passes downwards and backwards. The opening of the nasolacrimal duct into the inferior nasal meatus of the nasal cavity is partially covered by a mucosal fold (valve of Hasner or plica lacrimalis).

Excess tears flow through the nasolacrimal duct which drains into the inferior nasal meatus. This is the reason the nose starts to run when a person is crying or has watery eyes from an allergy, and why one can sometimes taste eye drops. This is for the same reason when applying some eye drops it is often advised to close the nasolacrimal duct by pressing it with a finger to prevent the medicine from escaping the eye and having unwanted side effects elsewhere in the body as it will proceed through the canal to the nasal cavity.

Like the lacrimal sac, the duct is lined by stratified columnar epithelium containing mucus-secreting goblet cells, and is surrounded by connective tissue.

Nasolacrimal canal

a = lacrimal gland b = superior lacrimal punctum c = superior lacrimal canal d = lacrimal sac e = inferior lacrimal punctum f = inferior lacrimal canal g = nasolacrimal canal The canal containing the duct is called the nasolacrimal canal. It is formed by indentations in the inferior nasal conchae, maxilla and lacrimal bone. The canal drains into the nasal cavity through the anterior portion of the inferior meatus, which is between the inferior concha and the floor of the nasal cavity.

Clinical significance

Obstruction of the nasolacrimal duct may occur. This leads to the excess overflow of tears called epiphora (chronic low-grade nasolacrimal duct occlusion). A congenital obstruction can cause cystic expansion of the duct and is called a dacryocystocele or Timo cyst. Persons with dry eye conditions can be fitted with punctal plugs that seal the ducts to limit the amount of fluid drainage and retain moisture.

During an ear infection, excess mucus may drain through the nasolacrimal duct in the opposite way tears drain.

In humans, the tear ducts in males tend to be larger than the ones in females.

Additional image

Image:Gray196.png|Roof, floor, and lateral wall of left nasal cavity File:Orbital bones.png|The seven bones which articulate to form the orbit. File:Gray1199.png|Outline of bones of face, showing position of air sinuses.

References

References

  1. (2020-02-19). "Nasolacrimal System Anatomy: Embryology, Puncta, Canaliculi".
  2. (2018). "Boorman's Pathology of the Rat". Elsevier.
  3. (2020-05-08). "Medical Definition of PLICA LACRIMALIS".
  4. CARREIRO, J. (2009). "Pediatric Manual Medicine". Elsevier.
  5. (2018). "Diagnostic Pathology of Infectious Disease". Elsevier.
  6. [http://www.childrenshospital.org/views/june06/blocked_tear_ducts.html "Blocked tear ducts in infants"] {{Webarchive. link. (2012-07-08 , ''Pediatric Views'', June 2006.)
  7. (2008). "Oculoplastic and Reconstructive Surgery". Elsevier.
  8. [https://www.wsj.com/articles/SB10001424052748703922804576300903183512350 "Tears of Men and Women Are Different"], ''[[Wall Street Journal]]'', mirrored at [https://www.foxnews.com/health/cry-me-a-river-why-men-and-women-shed-different-tears "Why Men and Women Shed Different Tears"], [[Fox News]], May 5, 2011.
Wikipedia Source

This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page.

human-eye-anatomy
Want to explore this topic further?

Ask Mako anything about Nasolacrimal duct — get instant answers, deeper analysis, and related topics.

Research with Mako

Free with your Surf account

Content sourced from Wikipedia, available under CC BY-SA 4.0.

This content may have been generated or modified by AI. CloudSurf Software LLC is not responsible for the accuracy, completeness, or reliability of AI-generated content. Always verify important information from primary sources.

Report