What is SALIVA and How Does it Work?

4 min


Saliva is a thin watery fluid that is produced by the salivary glands in our mouth. 

It is composed predominantly of water with electrolytes, mucus (a slimy substance), white blood cells, epithelial cells, enzymes, antimicrobial agents and lysozymes. These form the chunk of the components.

The organ producing saliva is called a salivary gland. 

The basic secretory unit of the salivary gland is called the acini. They produce saliva and distribute them through ducts or directly into the oral cavity.

Acini are like the fine tubes which produce saliva and pool them on to the salivary glands.

Now let’s see about the glands that produce saliva. They are predominantly classified into minor and major salivary glands.

Minor salivary gland

Numerous small salivary glands are present along the floor of the mouth, borders of the tongue, lips, and cheeks constitute the minor salivary gland.

The saliva from the minor salivary glands exits directly into the oral cavity. 

Major salivary gland:

There are 3 major salivary glands in our mouth. They are the parotid, submandibular and sublingual salivary glands.

Major salivary secrete the saliva produced through a proper ductal system that exits the saliva in the oral cavity. They are present in pairs. They produce the chunk of saliva constituting a whopping 80%.

Parotid gland: It is the largest major salivary gland located between the ear and the ascending branch of the lower jaw on both the right and left side of the cheek.

It secretes only serous type of saliva through the Stenson’s duct that opens in the buccal vestibule opposite to the upper second molar teeth.

Submandibular gland: is located along the side of the lower jaw bone with the duct opening into the floor of the mouth at the junction of the where the tongue meets the floor of the mouth.

It secretes the Seromucous saliva and also known as the mixed salivary gland.

Sublingual gland: It is located beneath the mucous membrane of the floor of the mouth near the chin region.

They have numerous ducts that empty near the junction of the tongue called the Rivinus ducts. The main duct of this gland is called Bartholin’s duct near the floor of the mouth. They secrete mucus saliva. 

FUNCTIONS OF SALIVA:

The functions of saliva are broadly classified into the following:

  • Digestive
  • Protective
  • Olfactory signals & thermoregulation.
  • Other functions like speech

Digestive functions:

The saliva contains salivary enzymes like amylase and lipase. The salivary amylase is secreted majorly in the parotid salivary gland and an adequate amount from the submandibular gland.

Carbohydrate Digestion:

Amylase contributes to the conversion of the starch into maltose in the oral cavity but their action is minimal in the stomach due to the change in the gastric environment into acidic.

Fat Digestion:

The salivary lipases present in the saliva secreted from the lingual serous salivary glands act in the stomach by initiating the digestion of the fats.

The saliva secreted while eating helps in chewing the food to form a bolus and swallowing them.

Protective functions:

Lubrication of the oral cavity is one of the primary functions of the saliva. This aids in proper phonation (speech), food passage and hydration of the tissues.

This maintains the viscosity, elasticity, and adhesiveness of the oral mucosa (lining of the mouth) surface. 

Saliva helps in soft tissue repair and wound healing as they promote the coagulation of the blood.

They help in the maintenance of the ecological balance by washing off the bacteria adhering to the oral cavity and maintaining of the oral pH.  They wash out the bacteria that are harmful to the teeth and mucosal surface. 

The secretory IgA which in turn inhibits bacterial activity and attachment thus protecting the tooth surface against dental caries formation. They aid in clump or aggregate formation of the bacteria thus inhibiting the adherence.

The salivary proteins like lactoferrin, lysozymes, and lactoperoxidase affect the ability of the oral bacteria to multiply or kill them directly acting as an antibacterial defense system.

Saliva acts as a mechanical barrier in limiting the penetration of a variety of potential irritants and toxins.

Saliva protects the teeth immediately after teeth eruption through the diffusion of ions like calcium, phosphorous, magnesium, fluoride and trace elements. It increases the surface hardness, decreasing the permeability and increasing the resistance against dental caries.

REASONS FOR EXCESS SALIVATION:

  • Systemic illness.
  • Morning sickness or nausea during pregnancy.
  • Sinus / tonsillar infections.
  • Poisonous reptile or snake bite.
  • Ulcers / inflammation / pain.
  • Poor oral hygiene.
  • Tuberculosis/rabies.
  • Jaw fracture / dislocations.

SPREAD OF INFECTION FROM SALIVA:

Saliva can spread the following infection:

  • Cold & flu viruses
  • Epstein-Barr viruses
  • Type 1 herpes viruses
  • Streptococcus bacterial infection.
  • Hepatitis B & C.
  • Cytomegalo virus.
  • Ebola virus (not yet confirmed still understudy)

Though HIV can be detected in the saliva it is not transmitted through saliva.

The microbes present in the saliva are Streptococcus species, Prevotella intermedia, Fusobacterium SPS. Etc. Any change in the oral environment results in the infection of the salivary gland due to this bacterial colonization.

SIGNS & SYMPTOMS OF SALIVARY GLAND INFECTION:

  • Decreased secretion of saliva.
  • Swollen salivary gland.
  • Dryness of the mouth.
  • Difficulty in chewing and swallowing.
  • Difficulty in speech.
  • Ulcers and pain near the glands.

SALIVARY STONES:

A calcified structure resembling a stone forms in the ducts of the salivary glands and block the flow of the saliva.

The submandibular gland is the most affected than the parotid or sublingual salivary glands.

They are composed of calcium salts. They are formed due to the consumption of antihypertensive drugs, antihistamines, psychiatric drugs, and bladder control drugs.

It is also caused by trauma to the glands or jaw dislocation.

Salivary stones result in:

  • Decreased saliva production / thick slimy saliva
  • dehydration of the oral cavity 
  • difficulty in eating and swallowing 
  • Pain & swelling of the salivary glands.

 SALIVA CAN BE TESTED FOR:

A mouth swab or spit is enough to reveal a lot of information about your health.

Once it is collected the saliva is sent to test for the following using PCR / high-performance liquid chromatography (HPLC) technique:

  • Alcohol
  • Cannabis
  • Marijuana
  • Cocaine
  • Opioids  (morphine)
  • Amphetamines
  • Antibodies to HIV
  • Steroids – Cortisol
  • Therapeutic drugs like theophylline, digoxin, methadone, etc.

Cortisol is present in saliva as free or unbound Cortisol. Evaluation of this helps us to identify the disorders of the adrenal gland. It is 90% accurate in most of the cases.

It can be used as a pre tester for athletes before any tournament. More the levels more stressed the athlete. So one can destress the athlete accordingly.

I hope this article has enlightened new arenas of saliva which you are not aware of. Do add comments to your thoughts.

REFERENCE:


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Dr Arun

Dr. Arun is a practicing dentist with more than 11 years of experience. Loves to blog and in constant search of new knowledge in dentistry and health niche.

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