We shed three types of tears-basal tears that provide lubrication and nourishment to the cornea: reflex tears that help remove irritation arising from foreign bodies or vapours; and psychic tears when experiencing strong emotions. The lacrimal glands in our eyes produce tears, which are mostly water, and some chemical components such as potassium and sodium. The salinity of tears is attributed to the presence of salts of sodium and potassium. The tears also contain oil, mucus and enzymes such as lysozyme. The salt, along with the enzymes, is responsible for keeping the comea healthy and microbe-free. The oil in basal tears stops them from evaporating or leaking out of the eyes.
This salinity of tears along with the presence of enzymes like lysozyme is responsible for their antimicrobial activity. Basal tears have a salt content similar to blood plasma. The salinity of basal tears disturbs the osmotic balance of bacteria and keeps the cornea in a healthy microbial-free environment. The mineral content of tears also nourishes the tissues associated with eyes. Saline nature of tears also indicates our evolutionary descent from marine organisms.
Picture Credit : Google
