Saliva: Function and Composition - QS Study
QS Study

Saliva is a colorless, viscus, opalcent fluid which is secreted by the 3 pairs of salivary glands – the parotid, submandibular, and sublingual glands. It is also secreted from buccal glands. It is a fluid that flows throughout the mouth, playing a significant function in bolstering and maintaining the health of oral soft and hard tissues. The digestive functions of saliva include moistening food, and helping to create a food bolus, so it can be swallowed easily.

It is important because it: keeps our mouth moist and comfortable and helps us chew, taste, and swallow.


(a) Total Secretion: 800- 1500 ml /day.

(b) pH =  6.0 – 7.0

(c) Nature: Slightly acidic

(d) S gravity: 1.002 – 1.012

(e) Type of Secretion:

  • Serous → that contains ptyalin
  • Mucous → that contains mucin.

Fig: Saliva glands


(A) Water: 99.5 %

(B) Solid: 0.5 %

  • Enzyme: ptyaline, Lingual lipase, carbonic anhydrase, phosphatase, lysozymes.
  • Other organics: Mucin, urea, cholesterol, amino acid.
  • Blood group subs: Ag of ABO blood group.
  • Inorganic subs: NaCl, KG, Na3PO4, Ca3(PO4)2, CaCO3, K HCO3
  • Cellular constituents: Yeast cell, bacteria protozoa etc.
  • Gasses: O2, N2, CO2.

Function of Saliva

(a) Mechanical functions:

  • It keeps the mouth moist and thus helps in speech
  • It facilitates swallowing.
  • It helps in preparing food staffs into a bolus, suitable for digestion.
  • It dilutes hot and irritant food thus prevents injury to a mucous membrane.
  • It acts as a lubricant.
  • It washes down the food debris, thereby prevents bacterial growth.

(b) Helps in taste: By dissolving food staffs, saliva helps in taking the sensation of taste.

(c) Digestive functions: It breaks down boiled starch into maltose due to the presence of enzyme ptyalin.

(d) Excretory functions: It excretes urea, some heavy metals (Pb, Bi, As etc), thiocyanates, Iodine, IgA, penicillin etc.

(e) Water Balance: It balances water by taking it.

(f) Buffering function: Due to the presence HCO3 and PO4-3 in saliva, its acts as a buffer.

(g) Bacteriolytic function: Saliva dissolves the many bacteria in the cell membrane, thereby kills them.