Facts about
TEAR GLANDS

The two small glands, one for each eye, which secrete the clear salty fluid that lubricates human eyes and eyelids and forms the tears. Each tear (or lactrimal ) glands is roughly the size of an almond and lies in the small crescentric space between the upper and outer part of the eyeball and the bony wall of the eye socket. Six or more tiny ducts emerge from the lower part of each gland and convey the secretion of the glad to the surface of the eye.

The secretion of each tear gland spreads over the surface of the eye and drains away through the tiny hole (punctum) which can be seen at the inner end of the lower lid. From there the fluid passes down into the nose - which is why the phenomenon of crying is usually accompanied by an increased need to blow the nose. If the punctum become blocked, the tears will constantly flow down the cheeks and a very minor operation may be necessary to relieve the obstruction. Normally, however, the secretion drains away imperceptibly. If the volume is greatly increased some of the secretion spills over the lower eyelids.

The most frequent cause of increased tear flow is a strong emotion, particularly sadness or great happiness, but an increase may occur also as a reflex response to irritation of the eye. Eye lashes and particle of grit are the most common irritants, but pepper and irritant chemicals such as ammonia vapour have similar effects. The eyelids then act as efficient windscreen wipers.

The tear gases used in war and riot control intensely irritate the eyes, and this and the great increase in the secretion of the tears cause partial and temporary blindness.