Let us know about the importance of Saliva, the liquid substance we perhaps don’t care for----part 1
It is a watery substance remains in the mouths of animals, including “social animals”, i.e. human being. Saliva is created by the salivary glands. But saliva is much more than water. Briefly speaking saliva contains 60 important components. That is why water or artificial saliva cannot match with natural saliva.
Components of saliva
The human saliva consists of 99.5 per cent water; the remaining 0.5 per cent is the other substances, such as antibacterial compounds like lysozyme and IgA, electrolytes, enzymes, mucus, glycoproteins.
The potent properties available in the saliva are protective, antimicrobial, digestive, coating, antiacid, homeostatic properties and lubricative elements.
Importance of enzymes in saliva
To begin the process of digestion of fats and dietary starches, enzymes are very essentials. For protecting our teeth from bacterial decay and breaking down the food particles which remain trapped within our dental crevices, the roles of these enzymes are equally important. Other than this, the initiation of swallowing, wetting food, lubricative functions and protecting the mucosal surfaces within the oral cavity are also done by these enzymes.
Contribution of saliva in the human body
Other than digestion food, saliva contributes to the maintenance of oral hygiene. The absence of saliva will significantly create oral hygiene problems, gingivitis or gum diseases, and dental caries.
i) Lubricating service
Our oral mucosa is protected from trauma by saliva at the time of eating, speaking and swallowing in a mechanical way. Those, who have saliva deficiency or xerostomia, suffer from mouth soreness. These people cannot manage chewing dry-fruits type of sticky things.
Moistening of food is one of the digestive functions of saliva. It also creates bolus and allows them to pass from our mouth through esophagus. Enzyme amylase or ptyalin is also another component of saliva. This component is helpful in breaking down starch into simpler sugars from starch and which are further broken down in the small intestine.
30 % of the digestion gets over within the mouth cavity. Salivary lipase is also secreted by salivary gland. Salivary lipase’s role is to begin to digest fat, especially for the new born, till the time their pancreatic lipase gets fully developed.
iii) Antimicrobial function
A non-specific immunologic action (e.g. lysozyme, myeloperoxidase and lactoferrin) and a specific (immunoglobulin, e.g. IgA) and a mechanical cleansing action are done by saliva. All these factors help in controlling the micro-organisms in the mouth. Besides this, it also carries out protective functions against the formation of dental plaque, which normally grows within the teeth lining. The other role it plays is washing away the sticky food particles from every place of the mouth cavity.
Saliva also is very instrumental in preventing the parotitis’ i.e. salivary glands’ ascending infections. Saving glands from any infection is the most important job saliva does.
iv) Buffer function, Ion reservoir
Saliva has supersaturated storage of many ions. A few salivary proteins blocks precipitation that causes formation of salt. These ions are known as buffer that keeps the acidity within a limited range. The ions also help in the prevention of the dissolving of the dental hard tissues. Another function of saliva is prevention of minerals before getting dissolved from the dental hard tissues.
v) Hormonal function
Gustin or Carbonic anhydrase is secreted by saliva. This is responsible for playing the role of developing taste buds.
vi) Role in taste
As far as sense of taste is concerned, saliva plays an important role. The liquid medium of saliva carries some chemicals to taste receptor cells. Those who have saliva deficiency complain about the reduced ability to taste; a few rather always complain about bad metallic taste.
vii) Wound licking
It is well known that animals lick their wounds and get healed. Although the NGF content is not found in the human saliva, but human saliva have some other chemicals which are helpful in case there is no clean water immediately available by the side but the wounds need to be protected from contaminations, before getting any medical help. In case pathogens are to be cleaned, licking is equally good for human being.
Saliva production is orchestrated by two factors: 1) parasympathetic nervous system and 2) sympathetic nervous system
Sympathetic nervous system:
Innervation of sympathetic stimulation produces thicker saliva. This saliva facilitates respiration.
Both sympathetic and parasympathetic nervous stimulation can cause contraction in myoepitheilium that leads to secretion in to the ducts and ultimately to the oral cavity.
Parasympathetic nervous system
The parasympathetic stimulation produces more watery saliva. This saliva facilitates digestion. Acetylcholine (ACh) is released onto salivary acinar cells by this type of stimulation, causing an enhanced intracellular calcium ion concentration. The enhanced calcium cells to fuse secretion. The system acts upon capillaries of the salivary glands and as a result, the blood vessels flow more blood to the acini, resulting to increased production of saliva.
Production of saliva (in human being)
Normally a human being produces 1.5 liters of saliva per day. The saliva production is typically done through diurnal circadian rhythm. The peak hour of producing saliva is in the mid-morning. The production gets decreased during day time and again picks up around early evening. The flow of saliva gets decreased at night. Several glands are involved in the production of saliva.
Daily production of saliva
It is a debated topic that how much saliva is produced in a day by a healthy person. It is estimated that between 0.75 to 1.5 litters of saliva is produced per day, but during sleep no saliva is produced. 75 % of human saliva is produced by submandibular gland while remaining 25 % is produced by parotid gland.
The normal quantity of saliva is sufficient for moisture and oral lubrication that assures comfort as well function for the individual.
The role of saliva is much more than only lubricating and moisturizing.