Dictionary > Tear

Tear

Definition
noun, plural: tears
(physiology) The watery secretion of the lacrimal glands
verb
To pull (apart) by force or by violence
Supplement
In physiology, the tears refer to the watery secretion of the lacrimal glands that serve to moisten the conjunctiva. The secretion is slightly alkaline and saline. They may also be in the form of drops of limpid, saline fluid, normally in small amount. Tears diffuse between the eye and the eyelids. The tears help lubricate or moisten the eyes. They are also a means to remove excess salt from food intake (see crocodile tears). Tears are produced when the lacrimal glands secrete lacrimal fluid that flow into the canals. These canals are connected to the lacrimal sac. From the sac, the tears, then drain through the lacrimal ducts into the space between the eyeball and lids. An excess of tears leads to the tears draining through the lacrimal duct onto the nasolacrimal duct, and finally into the nasal cavity. Accordingly, there are different types of tears.1 The basal tears contain water, mucin, lysozyme, lactoferrin, lipids, lacritin, lipocalin, immunoglobulins, electrolytes, etc. They are essential in keeping the eyes moist and free from dust. The reflex tears are tears resulting from eye irritations, and associated with coughing, yawning, and vomiting. The psychic tears are tears associated with strong emotions, such as grief, sorrow, pleasure, anger, etc. They are also associated with physical pain. Tears from emotions contain more hormones such as prolactin, adrenocorticotrophic hormone, and leu-enkephalin than the other two types of tears.
See also:

Related term(s):

  • Wear-and-tear pigment
  • Tear sac
  • Tear stone
  • Tear-thumb
  • Tear drop fracture
  • Tear film
  • Tear gas
  • Bucket-handle tear
  • Reference(s):

    1 Farandos, N. M., Yetisen, A. K., Monteiro, M. J., Lowe, C. R., & Yun, S. H. (2014). “Contact Lens Sensors in Ocular Diagnostics”. Advanced Healthcare Materials.


    You will also like...

    Birth of a Human Baby
    Birth of a Human Baby

    Following nine months inside the mother's womb is the birth of the baby. Know the different stages of the birthing proce..

    IQ, Creativity and Learning
    IQ, Creativity and Learning

    Human intelligence provided the means to utilize abstract ideas and implement reasoning. This tutorial takes a further l..

    An artist depiction of a Precambrian multicellular life form.
    The Evolution of Cell Organelles

    The nucleus containing the genetic material, DNA, and the mitochondria, well-identified as the "powerhouse of the cell",..

    Transpiration
    Water in Plants

    The movement of molecules (specifically, water and solutes) is vital to the understanding of plant processes. This tuto..

    Non-Mendelian Inheritance
    Non-Mendelian Inheritance

    In this tutorial, find out more about certain types of inheritance that does not follow the Mendelian inheritance patter..

    Angle Oak Tree
    Seed Plants

    Seed plants are vascular plants. They differ from the other vascular plants in producing seeds that germinate into a new..