TEAR DUCT AND GLAND,

also called Lachrymal, or Lacrimal, Duct And Gland, the structures that produce, distribute, and carry away tears (drops of clear saline fluid that are diffused between the eye and eyelid). Tears moisten the membrane that covers the eye (conjunctiva) and facilitate motion. Tears are also secreted as a reflex response to various stimuli, including irritants to the cornea, bright lights, and hot or peppery substances in the mouth. Tear flow that occurs in association with emotional upset is known as crying, or weeping. Each lachrymal gland lies in a slight hollow in the inner surfaces of the frontal bone, above the outer side of the eye. It is about the size and shape of a shelled almond and is divided by a fibrous partition into an upper and a lower portion, which projects into the back of the upper lid. Ducts from the gland discharge the tears from openings toward the outer side of the edge at the juncture of the conjunctiva lining the upper lid and that which covers the eyeball. Normal amounts of tears washing down over the front of the eyeball are kept from spilling out onto the cheeks by the oil that the lid glands deposit on the margins of the lids. Tears leave the eye by way of the two lachrymal ducts, which have barely visible openings (puncta lacrimalia) at the nasal end of the upper and lower lid margins. The lachrymal ducts lead to the lachrymal sac; this is an expanded extension of the nasal duct, through which the tears escape into the nasal cavity.