Sometimes, when you get mad at someone, you feel like spitting in his/her face. But you should know that saliva is not a worthless liquid to be wasted by spitting. It’s not at all like the material you discard from your kidneys and intestines and try to keep yourself clean from. Contrarily, our valuable secretion lets you taste your food, enables you to soften and swallow many hard foods, and helps you to prepare them for digestion in the stomach. If it weren’t for us, you couldn’t talk halfway decent, because your tongue would stick to the roof of your mouth. Your teeth would decay, cankers would appear, and you would be disturbed by your own bad breath, all due to the bacteria in your mouth.
We are three pairs of large glands that secrete into the mouth through canals and hundreds of very small glands around the throat. The large glands in front of the ear area are called the parotid glands, the glands under the chin are called the submandibular glands, and the ones under the tongue are called the sublingual glands. The parotid glands secrete saliva from the sides of the upper molar teeth, the submandibular glands from the front under the tongue, and the sublingual glands from many openings in the mouth’s base. There are also many more salivary glands in your inner cheeks and lips, and in all other wet spots in your mouth and throat.
Every sugary and starchy food you eat must first interact with our secretion in order to be digested. For this, an enzyme called ptyalin has been placed within us. But for this enzyme to work properly you must chew your food well. Also, you shouldn’t eat anything that is too hot or too cold, or anything that could change the pH (acidity) level of your mouth. Otherwise, this enzyme cannot function correctly. We produce an average of about 1000 milliliters (one liter) of secretion every day; however, we have the capacity to produce 1.5 liters of saliva per day.
Sometimes, the calcium in our enzymes may precipitate and form tartar due to acidic foods. Tartar can sometimes block our secretion canals. When you eat something, saliva production accelerates; but if our secretion canals are blocked by tartar, then the saliva cannot flow. This causes infection accompanied by severe pain and swelling. If our canals aren’t completely blocked, we may swell a little while eating, but we will slowly deflate after a while. Microbes can reproduce easier in accumulated saliva that cannot flow, thus causing severe pain and swelling. Our most frequently seen infection is the one that makes the parotid glands swell up, and is called the “mumps”. Even though it is seen more frequently in children, it may also be observed in adults. The swelling of both of the parotid glands is more frequent in alcoholics.
The thiocyanate ions that have been put in our saliva secretion kill the bacteria in your mouth by breaking them apart. In addition, lysozyme enzymes attack and kill bacteria in your mouth while digesting food remains to prevent the bacteria to feed and reproduce. Hungry bacteria perish more easily. Our infinitely merciful Lord put special proteins called anticorps in our saliva to prevent many diseases that can enter from the mouth before they develop. These anticorps act like special agents that attack and destroy bacteria. If we don’t secrete enough saliva, ulcers will develop in your mouth frequently. If they last long enough, they will get infected and also cause tooth decay.
The control of our secretion is connected to an area that includes the appetite center in the brain stem through the involuntary nervous system. When you smell or taste foods you like, we immediately start secreting saliva as a reflex. When you come across foods that you don’t like, or when you get scared or excited, we slow down saliva production, again reflexively. Suspects in the past used to be given a handful of rice to swallow, with the thought that the real culprit would not be able to swallow them, because the excitement caused by the feeling of guilt would cause his/her mouth to dry.
Diabetes, which is a systemic illness, also has a negative effect on our functioning. Diabetes presents itself with drying of the mouth, along with excessive intake of water, and the frequent need to visit the restroom. One type of rheumatoid arthritis may also cause dry mouth and dry eyes together with joint pain.
As you see, Peter, I’ve briefly explained to you how invaluable and necessary your saliva is. I have not even mentioned our histological and anatomical structure, which resembles a bunch of grapes. I believe you can imagine how each and every one of my gland cells is like a perfect biochemical factory. You wouldn’t relate all these to your mouth being wet for no reason, would you?
Irfan Yilmaz is a professor of biology in Dokuz Eylul University, Izmir, Turkey.