Tears

For other uses, see Tears (disambiguation).
Human tears

Tears are a clear liquid secreted by the lacrimal glands (tear gland) found in the eyes of all land mammals.[1] Tears are made up of water, electrolytes, proteins, lipids, and mucins that form layers on the surface of eyes.[2] The different types of tears—basal, reflex, and emotional—vary significantly in composition.[2]

Anatomy of lachrymation, showing
  • 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 functions of tears include lubricating the eyes (basal tears), removing irritants (reflex tears), and also aiding the immune system.[3] Tears also occur as a part of the body's natural pain response.[4] Emotional secretion of tears may serve a biological function by excreting stress-inducing hormones built up through times of emotional distress.[5][6] Tears have symbolic significance among humans.[4]

  1. ^ "Definition of TEAR". www.merriam-webster.com. Retrieved 2019-08-04.
  2. ^ a b Cite error: The named reference ReferenceA was invoked but never defined (see the help page).
  3. ^ Farandos, NM; Yetisen, AK; Monteiro, MJ; Lowe, CR; Yun, SH (2014). "Contact Lens Sensors in Ocular Diagnostics". Advanced Healthcare Materials. 4 (6): 792–810. doi:10.1002/adhm.201400504. PMID 25400274. S2CID 35508652.
  4. ^ a b "Why do we cry? The scientific reasons behind sobbing". The Independent. 2014-09-18. Archived from the original on 2022-05-26. Retrieved 2019-08-04.
  5. ^ "All About Emotional Tears". American Academy of Ophthalmology. 2017-02-28. Retrieved 2019-08-04.
  6. ^ Frey, W. H.; DeSota-Johnson, D.; Hoffman, C.; McCall, J. T. (October 1981). "Effect of stimulus on the chemical composition of human tears". American Journal of Ophthalmology. 92 (4): 559–567. doi:10.1016/0002-9394(81)90651-6. ISSN 0002-9394. PMID 7294117.