BIOCHEMICAL ASPECTS OF SALIVA FLUID

1. By
Dr KHALED ALGARIRI
CAMS- QASSIM UNIVERSITY
March2020

2. Saliva
 It is a watery secretion in the mouth produced by the salivary
glands that aids in the digestion of food.
 It serves as an aid to swallowing and digestion by moistening
and softening food.

3. Major salivary gland: 93% of
saliva by volume is secreted by
major salivary glands, these are:
1. Parotid
2. Submandibular
3. Sublingual glands
Minor salivary glands:
Contributes to remaining 7% of salivary vol.
These minor glands are typically located in
the submucosa and have short ducts
opening directly onto the mucosal surface

4. SALIVARY GLANDS
• Salivary glands are made up of secretory acini and ducts.
• The basic secretory units of salivary glands are clusters
of cells called an acini .
• There are two types of secretions - serous and mucous.
• The acini can either be serous, mucous, or a mixture of
serous and mucous.

5. FORMATION OF SALIVA
The formation of saliva takes place in two stages
• First stage, the secretory acini produces an isotonic
primary saliva with ionic composition is similar to that of
plasma.
Second stage, the primary saliva is modified as it passes
through the duct system by selective reabsorption of Na+
and Cl- (but not water) and some secretion of K+ and HCO3-

6. • The final saliva is secreted into the mouth. Thus, it becomes
hypotonic with salt concentration below that of primary
saliva.

8. The Functions of Saliva
(1) lubrication and protection,
(2) buffering action and clearance,
(3) maintenance of tooth integrity,
(4) antibacterial activity
(5) taste and digestion

9. (1) Lubrication and Protection
 As a seromucous coating, saliva lubricates and protects oral tissues,
acting as a barrier against irritants.
 These irritants include,proteolytic and hydrolytic enzymes produced in
plaque,potential carcinogens from smoking and exogenous
chemicals, and desiccation from mouth breathing.
 The best lubricating components of saliva are Mucins that are
excreted from minor salivary glands..
 Mastication, speech, and swallowing all are aided by the lubricating
effects of mucins.

10. 2- Buffering action and Clearance
• The buffering action of saliva works more efficiently during
stimulated high flow rates but is almost ineffective during
periods of low flow with unstimulated saliva.
• Phosphate is likely to be important as a buffer only during
unstimulated flow.

11. • The pH of saliva may not be
as important a measure for
buffering action on caries as
the pH of plaque, which
saliva modifies. Remaining
fermentable Carbohydrates
and the buffering capacity of
saliva affect plaque pH,
unless the pH of the plaque
is too low For bacterial
enzymes to function.

12. • The resting pH of plaque (that is, the pH of plaque 2 to 2.5
hours after the last intake of exogenous carbohydrates) is
6 to 7.3,The pH rises during the first 5 minutes after the
intake of most foods.
The pH then falls to its lowest level, to 6.1 or lower, approximately 15
minutes after food consumption. Unless there is additional ingestion of
fermentable carbohydrates, the pH of plaque gradually

13. Thus, salivary buffering, clearance, and flow rate work in
concert to influence intraoral pH. So flow can be
augmented by the stimulus of chewing as well as by the
muscular activity of the lips and tongue. • With stimulated
additional flow, chewing products (such as gum) that
contain no fermentable carbohydrates can aid in the
modulation of plaque pH

14. Maintaining tooth integrity
Maintaining tooth integrity is a one that facilitates the demineralization
and remineralization process.
Demineralization occurs when acids diffuse through plaque and the
pellicle into the liquid phase of enamel between enamel crystals.

15. • Resulting crystalline dissolution
occurs at a pH of 5 to 5.5, which is
the critical pH range for the
Development of caries.
• Remineralization is the process of
replacing lost minerals through the
organic matrix of the enamel to the
crystals.

16. Supersaturation of minerals in saliva is critical
to this process. The high salivary concentrations of
calcium and phosphate, which are maintained by
salivary proteins, may account for the maturation
and remineralization of enamel.
Statherin, a salivary peptide, contributes to the
stabilization of calcium and phosphate salts
solution,serves as a lubricant to protect the tooth
from wear.
The presence of fluoride in saliva
speeds up Crystal precipitation,
forming a fluorapatite-like coatingmore
resistant to caries than the original
tooth structure.
Fluoride in salivary solution
works to inhibit dissolution of
apatite crystals.

17. Buffering action and clearance
• Buffering action and clearance of saliva through the following
components: bicarbonate, phosphate, urea, and amphoteric
proteins and enzymes.
• Bicarbonate is the most important buffering system. It diffuses
into plaque and acts as a buffer by neutralizing acids.
• Moreover, it generates ammonia to form amines, which also
serve as a buffer by neutralizing acids.
• Urea, another buffer present in saliva, releases ammonia
after being metabolized by plaque and thus increases plaque
pH.

18. Antibacterial activity
 Salivary glands are exocrine glands, and, as such, secrete fluid containing
immunologic and nonimmunologic agents for the protection of teeth and
mucosal surfaces.
 Immunologic contents of saliva include secretory IgA, IgG, and IgM.
 Secretory IgA, the largest immunologic component of saliva, is an
immunoglobulin produced by plasma cells in connective tissues and translocated
through the duct cells of major and minor salivary glands.
 IgA, while active on mucosal surfaces, also acts to neutralize viruses,serves as
an antibody to bacterial antigens, and works to aggregate or clump bacteria, thus
inhibiting bacterial attachment to host tissues.

19. • Nonimmunologic antibacterial salivary contents such as
proteins, mucins, peptides, and enzymes
(lactoferrin,lysozyme, and peroxidase), all products of
acinar gland cells, help protect teeth against physical,
chemical, and microbial insults.

21. The Functions of Saliva

22. The Functions of Saliva

25. ROLE OF SALIVARY ENZYMES
Salivary enzymes can be produced by salivary glands
• 1. aspartate and alanine aminotransferases (AST and ALT)
• 2. lactate dehydrogenase (LDH)
• 3. gamma-glutamyl transferase (GGT)
• 4. creatine kinase (CK)
• 5. alkaline phosphatase (ALP)
• 6. acidic phosphatase (ACP)

26. Major Enzymes in Saliva
•Salivary amylase (also known as ptyalin) breaks down
starches into smaller, simpler sugars.
•Salivary kallikrein helps produce a vasodilator to dilate blood
vessels.
•Lingual lipase helps to break down triglycerides into fatty
acids and glycerides.

27. Salivary Amylase
Salivary amylase is the primary enzyme in saliva. Salivary amylase breaks down
carbohydrates into smaller molecules, like sugars. Breaking down the large
macromolecules into simpler components helps the body to digest starchy foods,
like potatoes, rice, or pasta.
During this process, larger carbohydrates, called amylopectin and amylose, are
broken down into maltose. Maltose is a sugar that is composed of individual
subunits of glucose, the human body's key source of energy.
Salivary amylase also has a function in our dental health. It helps to prevent
starches from accumulating on our teeth. In addition to salivary amylase, humans
also produce pancreatic amylase, which further breaks down starches later in the
digestive process.

28. Salivary Kallikrein
As a group, kallikreins are enzymes that take high molecular
weight (HMW) compounds, like kininogen, and cleave them to
smaller units. Salivary kallikrein breaks down kininogen
into bradykinin, a vasodilator. Bradykinin helps to control
blood pressure in the body. It causes blood vessels to dilate or
expand and causes blood pressure to be lowered. Typically,
only trace amounts of salivary kallikrein are found in saliva.

29. Lingual Lipase
 Lingual lipase is an enzyme that breaks down triglycerides into
glycerides and fatty acid components, thus catalysing the digestion of
lipids. The process begins in the mouth where it breaks down the
triglycerides into diglycerides. Unlike salivary amylase, which
functions best in non-acidic environments, lingual lipase can operate
at lower pH values, so its action continues into the stomach.
 Lingual lipase helps infants digest the fats in their mother's milk. As
we get older, the relative proportion of lingual lipase in saliva
decreases as other parts of our digestive system help with fat
digestion.

30. • Other Minor Salivary Enzymes
• Saliva contains other minor enzymes, like salivary acid
phosphatase, which frees up attached phosphoryl groups from
other molecules. Like amylase, it helps with the digestion
process.
• Saliva also contains lysozymes. Lysozymes are enzymes that
help to kill bacteria, viruses and other foreign agents in the
body. These enzymes thus perform antimicrobial functions.