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Saliva in Mouth, Composition and Functions

Saliva in Mouth is a clear liquid made by several glands in your mouth area. Saliva is an important part of a healthy body. It is mostly made of water. But saliva also contains important substances that your body needs to digest food and keep your teeth strong.

Three major paired glands- the parotids, submandibular and sublingual, and numerous minor glands throughout the mouth normally produce saliva. There is much debate about the amount of saliva that is produced in a healthy person per day; estimates range from 0.75 to 1.5 liters per day while it is generally accepted that during sleep the amount drops to almost zero. In humans, the submandibular gland contributes around 70–75% of secretion, while the parotid gland secretes about 20–25% and small amounts are secreted from the other salivary glands.

The oral cavity is almost constantly flushed with saliva, which floats away food debris and keeps the mouth relatively clean. Saliva also contains lysozyme, an enzyme that lyses many bacteria and prevents overgrowth of oral microbial populations.


Composition of Saliva:-

Produced in salivary glands, human saliva is 99.5% water, but it contains many important substances, including electrolytes, mucus, antibacterial compounds, and various enzymes.

It is a fluid containing:

  • Water
  • Electrolytes
    • 2–21 mmol/L sodium(lower than blood plasma)
    • 10–36 mmol/L potassium (higher than plasma)
    • 1.2–2.8 mmol/L calcium (similar to plasma)
    • 0.08–0.5 mmol/L magnesium
    • 5–40 mmol/L chloride (lower than plasma)
    • 25 mmol/L bicarbonate (higher than plasma)
    • 1.4–39 mmol/L phosphate
    • Iodine (mmol/L concentration is usually higher than plasma, but dependent variable according to dietary iodine intake)
  • Mucus (mucus in saliva mainly consists of mucopolysaccharides and glycoproteins
  • Antibacterial compounds (thiocyanate, hydrogen peroxide, and secretory immunoglobulin A
  • Epidermal growth factor (EGF)
  • Various enzymes; there are three major enzymes found in saliva:
    • α-amylase (EC3.2.1.1), or ptyalin, secreted by the acinar cells of the parotid and submandibular glands, starts the digestion of starch before the food is even swallowed; it has a pH optimum of 7.4
    • Lingual lipase, which is secreted by the acinar cells of the sublingual gland; has a pH optimum around 4.0 so it is not activated until entering the acidic environment of the stomach
    • Kallikrein, an enzyme that proteolytically cleaves high-molecular-weight kininogen to produce bradykinin, which is a vasodilator; it is secreted by the acinar cells of all three major salivary glands
    • Antimicrobial enzymes that kill bacteria
      • Lysozyme
      • Salivary lactoperoxidase
      • Lactoferrin
      • Immunoglobulin A
    • Proline-rich proteins (function in enamel formation, Ca2+-binding, microbe killing, and lubrication)[12]
    • Minor enzymes include salivary acid phosphatases A+B, N-acetylmuramoyl-L-alanine amidase
  • Cells: possibly as many as 8 million humans and 500 million bacterial cells per mL. The presence of bacterial products (small organic acids, amines, and thiols) causes saliva to sometimes exhibit foul odor
  • Opiorphin, a pain-killing substance found in human saliva
  • Haptocorrin, a protein which binds to Vitamin B12 to protect it against degradation in the stomach, before it binds to intrinsic factor

What is the Function of the Saliva?

  1. Chemical digestion breaks down starch by the function of “salivary amylase”
  2. Helps to chew and swallowing
  3. Lubricating effect: moisturizes the inside of the mouth and creates smoother speech
  4. Solvent effect: dissolves food and allows the tongue to taste food
  5. Cleaning effect: washes away food debris and bacteria remaining in the mouth
  6. Antibacterial effect: Lysozyme, peroxidase and lactoferrin fight against pathogenic microorganisms
  7. pH buffering effect: Prevents sudden changes in pH
  8. Supplies minerals, including calcium and phosphorus, to teeth
  9. Help to keep dentures securely in place
  10. Has proteins and minerals that protect tooth enamel and prevent tooth decay and gum disease

A very important fact to remember when battling bad breath is that saliva is our friend. The flow of saliva diminishes considerably during sleep, allows populations of bacteria to build up in the mouth- the result is dragon breath in the morning. A dry mouth represents the perfect environment for odor-causing bacteria. Sali9va acts as nature’s mouth wash by keeping the mouth moist, washing away bacteria, and dissolving foul-smelling volatile sulfur compounds.

Conditions that reduce saliva flow or which make our mouth dry can, therefore, lead to bad breath. In fact, the morning breath which many people experience after a long night of sleep is caused by the reduction in saliva flow that occurs when we sleep.

Dieting, fasting or talking for long periods of time reduce saliva flow and contribute to bad breath. In addition, certain medications, alcohol consumption, and breathing through the mouth during exercise cause dry mouth contributing to the problem.

How do you make sure your Saliva flow is adequate and that your mouth stays moist?

  • Drink water. Saliva flow increases when we eat or drink. If you are dieting or fasting, drinking water is a good way to stimulate the flow of saliva. The water will also help to wash away food and bacteria.
  • Placing a drop of lemon juice on the tip of your tongue or chewing sugarless gum are also effective ways to stimulate saliva flow. It is a commonly held notion in the medical community that mints and breath-freshening gums work not by masking odor but by stimulating saliva flow.
  • Eat fibrous foods. Here’s another reason for eating an apple a day: Crunchy, fibrous fruits and vegetables like apples, carrots, and celery are mildly abrasive, so they sweep bacteria and plaque off teeth.
  • Taking soup at room temperature can also increase saliva secretion, especially if you add fresh tomato slices or a little tomato juice. Sipping some water with a little vitamin C powder added, sucking on ice-cubes, or chewing gum containing xylitol may also help.

Dental Health Guide, Providing information on dental care and dental hygiene along with detailing the most common dental diseases with symptoms and treatment methods. Readers should use the dental articles as reference only and consult a dentist and visit a dental clinic for dental health problems.