Tears are produced by the lacrimal (tear) glands, which are situated above each eyeball. The glands continually secrete a small amount of salty fluid that is distributed over the surface of the eyes through the action of blinking and drain into the nose. Tears form a protective film that lubricates the eye and flushes out any dust and dirt. They also contain an antibacterial ingredient. Tear production increases when you cry or if the eye is irritated by a chemical or foreign particle.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.