Saliva or spit is a watery substance produced in the mouths of many animals, including humans, and is a vital element of their digestive process. Saliva basically commences the digestive process by moistening the ingested food. This watery, often frothy, substance is produced in the salivary glands. There are three pairs of salivary glands in most animals. The parotid glands are found in the cheeks - precisely speaking, at the base of each ear. The sub-mandibular glands are located at the base of the mouth - close to the jaw. The third pair of the salivary glands that are found below the tongue are known as sublingual glands.
Constituents in saliva
Saliva is composed of a blend of water and other substances dissolved in it and known as enzymes, electrolytes and mucus. In addition to these, saliva also comprises potassium, bicarbonate and sodium. The major constituent of saliva or spit is water, amounting to 99 per cent of its content. However, the remaining substances too have a crucial role in the digestive process. The bicarbonate present in saliva may perhaps be particularly imperative since it has the aptitude to neutralize or counteract a number of acids produced or secreted in the stomach.
In addition to the bicarbonate, the enzymes that make up saliva are also especially important. Particularly, one of these enzymes called ptyalin, a member of the amylase family of enzymes, works to disintegrate the starch content in the foods we consume, commencing the vital processes involved in digesting or assimilating the foods into our body. In fact, ptyalin commences the digestive process right inside the mouth, even before the ingested food enters the stomach.
Similarly, the tiny proportion of mucus that composes saliva is also important. This way, all constituents of saliva are of great importance in the digestive process of several animals, including the humans.
Many may want to know why saliva is so important for the digestive process. For the uninitiated, it may be informed that when there is an impulse to vomit the food we are eating, the brain emits signals to the mouth to enhance the production of saliva. Enhanced salivation in the mouth helps to neutralize the hazardous effects of the acids produced in the stomach. In fact, when these acids reach the mouth they may be somewhat harmful inside the mouth, teeth and throat. In other words, saliva helps in preventing vomiting in such conditions.
There are numerous benefits of saliva and one may go on carry on describing them. For instance, saliva works as a lubricant for the food and helps in swallowing it as well as in its passage through the esophagus without any uneasiness. In addition, it helps to make dry foods soluble thereby enabling an individual to taste its flavour or what he/ she is eating. Last, but not the least, saliva also helps in oral hygiene by eliminating the useless microorganisms and bacteria from the mouth. This way, one may continue describing the numerous benefits of saliva. It may, however, be noted that salivation or production of saliva by the parotid glands are slow during the night which creates "morning breath".
You may often find various animals, including humans, lick their wounds. This is primarily owing to the fact that saliva possesses anti-bacterial properties. It contains trace amounts of hydrogen peroxide which helps to eliminate unwanted or harmful microbes, including bacteria. Thus, when an animal licks its wounds, it means that the lesion is being cleaned better than using water. Looking at the things from this perspective, it may be said that this is possibly the reason why many animals, including humans, intentionally do not use water very often to wash or clean out minor wounds - we just lick them and this facilitates the healing process.
In addition, it has been demonstrated that in a number of animals, especially mice, saliva encloses a substance called the nerve growth factor or NGF. This substance, NGF is basically extremely capable of healing wounds very fast. Moreover, it has also been observed that when an animal which is wounded licks the lesion or applies a dosage of NGF contained in its saliva, the wound heals at least two times faster than a situation where NGF is not applied to the lesion. Unfortunately enough, the saliva produced by humans does not contain the substance NGF. Nevertheless, scientists around the world are working to find out whether the human saliva also contains traces of the nerve growth factor (NGF).
Precisely speaking, saliva may be described as an endowment for the animals that have the ability to produce it. However, normally people do not realize the importance of saliva and generally undervalue it or its importance in our daily life.
Creation and discharge of saliva
The automatic nervous system that regulates all our involuntary actions also controls the production of saliva in the mouth. The stimulation of the brain, for instance, by the aroma of foods, emits signals to the salivary glands located in the mouth. On receiving the signals from the brain, specific cells in the mouth called acinar cells undertake the production of saliva. The serous cells (also known as acinar cells) of the salivary glands produce a weak watery form of saliva, while the mucous cells produce dense and sticky saliva. It may be noted that the parotid salivary glands are mostly composed of serous cells. The salivary glands that are found at the base of the tongue are typically made up of mucous cells, while the sub-mandibular glands comprise a mixture of both these types of cells - serous and mucous. The saliva produced by the acinar cells accumulates in tiny ducts where it can be altered. These small ducts are connected to larger ducts, which ultimately discharge the saliva into the mouth.
As aforementioned, saliva is a very useful substance produced by our body since it has multiple uses, especially in facilitating the digestive processes. In fact, when the production of saliva drops people miss it very much and it results in dry mouth. Apart from facilitating the digestive process in several animals, including humans, saliva is also important for oral hygiene. Interesting enough, there are a few animals which have modified saliva for other uses too. For instance, especially swifts produce gummy or sticky saliva that they use as a glue to hold their nests together.
Lubricating the food to make chewing and swallowing it easier and effortless is one of the major functions of saliva. The fluid also helps in maintaining the interiors of the mouth moist and humid. In other words, saliva helps to maintain the mucus linings in the mouth damp, thereby preventing them from causing to undergo any type of distress or cracking. People who are familiar with having a dry mouth know that when there is a deficit of saliva in the mouth it not only causes great discomfort, but also makes eating difficult because the food remains hard and it is troublesome chewing and swallowing it down the esophagus.
Saliva is composed of different types of enzymes and each of them have different functions to perform. For instance, the enzyme lysozyme possesses anti-bacterial properties and, thus, it is helpful in controlling the bacteria found in the mouth and maintains their presence at a level that is manageable. Amylase is another enzyme found in saliva and it works as a digestive agent breaking down the food in the mouth itself and much before it reaches the stomach for actual digestion. The role of amylase makes the job of the stomach easier. However, it is important to note that if the balance of the enzymes in the saliva is disturbed, it may result in health problems - especially the process of eliminating the harmful bacteria from the mouth becomes difficult or the process is affected giving rise to several oral health problems.
Saliva produced by the acinar cells in the mouth also contains several minerals that are deposited on the teeth on a regular basis making the teeth stronger and fortifying them against any harm that may be caused by the bacteria present in the mouth. However, in a number of instances, the mineral deposits may be in excess and this may result in the development of plaque. In addition, the digestive enzymes found in saliva also facilitate in dissolving the food particles that get stuck between the teeth. This action of the digestive enzymes in saliva is important since it makes certain that the teeth do not decay due to these food particles and, at the same time, it helps to maintain the oral hygiene.
While saliva is extremely useful in numerous ways, it is best when it remains in the mouth. Although saliva possesses a number of anti-bacterial properties, it is advisable that this substance should never be used in the same manner as other anti-bacterial agents since the mouth is not sterile naturally. However, many people believe it to be otherwise. While applying saliva to wounds often facilitates their healing, it may also prove to be detrimental as it has the aptitude to introduce the bacteria found in the mouth to the bloodstream, which is never desirable. At the same time, it is possible that saliva may at times shelter a number of viruses. This is the primary reason why people are generally advised to avoid kissing people who may be suffering from some ailment.
Disorders related to salivary glands
The benefits of saliva notwithstanding, as in the instance of other areas of the human body, there are many things that may go wrong with saliva too. The list of potential disorders that may affect the salivary glands is quite long and any of these potential disorders may constrict the amount of saliva produced in an individual's mouth and also cause immense pain and uneasiness to the person. It is disgusting to note that the salivary glands may be affected by tumor growths, be obstructed by stones, may be infected or even abscessed and also reduce production of saliva owing to the side effects of some other ailment. In addition, the salivary glands may also be affected by specific drugs. The list of such problems is too long and all of them very disgusting, of course.
However, happily enough, majority of the disorders related to the salivary glands can be cured by the modern-day medical system. While some of them may be treated effectively using medicines, a number of others might require surgery, which of course is more expensive and the last resort. Therefore, people enduring any of the disorders related to the salivary glands need not lose hope or be nervous and lose their sleep over their health condition. Nevertheless, all individuals ought to definitely understand the value of such small things that make our body function as a fine-tuned machine, which it actually is.