Each eye has a tear-producing gland, which are konwn as " Lacrimal Gland" . They are situated in the upper lateral region of each orbit, behind the upper eyelid edge and secrete the aqueous layer of the tear film. In the following, the ophthalmologists of Noor Eye Hospital provide you with useful information on lacrimal ducts.
Tear film layers
1.The innermost layer of the tear film is mucous layer, produced and secreted by the conjunctival goblet cells.
2. The middle layer is the thickest layer of tear film and in fact it is like a solution of water and salt . This layer, produced by lacrimal glands in eyelids, keeps the eye hydrated, cleanses the eye and washes away foreign particles or irritants. Problem in the secretion of this watery layer of the tear film is the most common cause of dry eye, which is so- called "keratoconjunctivitis sicca".
3. The outermost layer of the tear film is the very thin oil layer، produced by the meibomian glands in the eyelids. Its main task is prevent the evaporation of the underlying watery layers of the tear film.
Tears pass over the eye surface to the lacrimal ducts, through the two small openings, punctum, located on the inner edges of the upper and lower eyelids and then pass into the lacrimal sac, which is next to the inner corner of the eyes (between the eyes and the nose). From the lacrimal sacs, tears move down through the nasolacrimal duct and drain into the back of the nose. That's why you usually get a runny nose when you cry. Therefore, the tear system consists of lacrimal glands, lacrimal ducts, the lacrimal sac and nasolacrimal duct.