Why do tears come when we are in grief?
Tear is a salty fluid, fully filled with protein (prolactin that converts to before human milk, water, mucus and oil, released from the lacrimal gland found in the upper, outer region of our eyes. Usually humans produce excessive tears in emotional contexts than other animals.
Of course, not all tears are of the emotional variety. In fact, three types of tears exist, all with different purposes. Basal tears are omnipresent in our eyes.
These constant tears are what keep our eyes from drying out completely. The human body produces an average of 5 to 10 ounces of basal tears each day. They drain through the nasal cavity, which is the reason so many of us develop runny noses after a good fest.
The second type is reflex tears, which serve to protect the human eye from harsh irritants such as smoke, onions or even a very strong, dusty wind.
To accomplish this feat, the sensory nerves in our cornea communicate this irritation to our brain stem, which in turn sends hormones to the glands in the eyelids. These hormones cause the eyes to produce tears, effectively ridding the irritating substance.
The third type of tears is emotional tears. It all starts in the cerebrum where sadness is registered. The endocrine system is then triggered to release hormones to the ocular area, which then causes tears to form. Emotional tears are common among people who see their mother die or who suffer personal losses.
Human emotions induce a physiological stress that does not exist in other mammals and requires tears to cope with it. The physiology of human eyes is somehow different from eyes of other mammals, such that it requires an excessive production of tears at circumstances other than physical or physiological stress.
Human emotional tears are a byproduct of the unique evolution of a substantial cranial reduction in subnasal prognathism, and increased encephalization. Hypothetically, these developments may have constrained and sensitized the human tear ducts and sinuses when certain emotions are high.
The phrase “having a good cry” suggests that crying can actually make you feel physically and emotionally better, which many people believe.
Some scientists agree with this theory, asserting that chemicals build up in the body during times of elevated stress. They also believe that emotional crying is the body's way of ridding itself of these toxins and waste products.
In fact, one study collected both reflex tears and emotional tears (after peeling an onion and watching a sad movie, respectively).
When scientists analyzed the content of the tears, they found each type was very different. Reflex tears are generally found to be about 98 per cent water, whereas several chemicals such as a protein called prolactin (precursor of breast milk), adrenocorticotropic hormones (indicator of high stress level) and an endorphin that reduces pain and works to improve mood are commonly present in emotional tears.