Saliva enzymes are necessary for the initial stages of digestion of dietary carbohydrates and lipids. These enzymes also aid in the breakdown of food particles trapped in tooth fissures, hence preventing bacterial decay. Saliva also acts as a lubricant, moistens food and allows swallowing to begin, as well as it prevents the oral mucosa from drying out.
Saliva serves a variety of animal species in ways that go beyond predigestion. Swifts make nests with their gummy saliva. Bird’s nest soup is made from the nests of Aerodramus. Cobras, vipers, and other members of the venom clade hunt with fangs that inject deadly saliva. Silk fibre is produced by caterpillars using silk proteins stored in specialised salivary glands.
Composition
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- Human saliva is made up of 99.5 percent water, but it also contains a variety of vital chemicals such as electrolytes, mucous, antibacterial agents, and enzymes.
- 99.5 percent water
- Electrolytes:
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- Sodium concentrations of 2–21 mmol/L (lower than blood plasma)
- Potassium concentrations of 10–36 mmol/L (higher than plasma)
- Calcium concentrations of 1.2–2.8 mmol/L (similar to plasma)
- Magnesium concentrations of 0.08–0.5 mmol/L
- Chloride concentrations of 5–40 mmol/L (lower than plasma)
- Bicarbonate, 25 mmol/L (higher than plasma)
- Phosphate concentrations of 1.4–39 mmol/L
- Iodine (mmol/L concentration is normally greater than plasma, however dietary iodine intake is a dependent variable)
- Mucus is a type of mucus that is (mucus in saliva mainly consists of mucopolysaccharides and glycoproteins)
- Antibacterial substances (thiocyanate, hydrogen peroxide, and secretory immunoglobulin A)
- EGF (epidermal growth factor) is a protein that is produced (EGF)
- Various enzymes, like -amylase (EC3.2.1.1) or ptyalin, released by the acinar cells of the parotid and submandibular glands, start the digestion of starch even before the food is ingested; it has a pH optimum of 7.4.
- The acinar cells of the sublingual gland release lingual lipase, which has a pH optimum of around 4.0 and is not activated until it reaches the acidic environment of the stomach.
- All three primary salivary glands secrete kallikrein, an enzyme that proteolytically cleaves high-molecular-weight kininogen to create bradykinin, a vasodilator.
- Bacterial-killing antimicrobial enzymes:
- Lysozyme
- Lactoperoxidase from saliva
- Lactoferrin
- Immunoglobulin A
- Enamel creation, Ca2+ binding, microbe killing, and lubricating are all functions of proline-rich proteins.
- Salivary acid phosphatases A+B, N-acetylmuramoyl-L-alanine amidase, NAD(P)H dehydrogenase (quinone), superoxide dismutase, glutathione transferase, class 3 aldehyde dehydrogenase, glucose-6-phosphate isomerase, and tissue kallikrein are only a few of the minor enzymes (function unknown)
- Cells: up to 8 million human and 500 million bacterial cells per millilitre. Saliva can have a bad odour due to the presence of bacterial products (small organic acids, amines, and thiols).
- Human saliva contains opiorphin, a pain killing chemical.
- Before it binds to an intrinsic factor, haptocorrin binds to vitamin B12 to protect it from breakdown in the stomach.
Daily salivary output
Experts disagree about how much saliva a healthy person generates. The amount produced every day is thought to be 1500ml, and researchers agree that it decreases dramatically during sleep. The submandibular gland secretes roughly 70 to 75 percent of saliva in humans, whereas the parotid gland secretes about 20 to 25 percent; the other salivary glands secrete tiny quantities as well.
Functions
Saliva aids in the digestion of meals and the preservation of oral hygiene. Dental caries, gum disease (gingivitis and periodontitis), and other oral issues become far more common when salivary function is impaired. [requires citation] Saliva inhibits the growth of bacterial infections and plays an important role in maintaining systemic and oral health by preventing tooth decay and removing sugars and other microbial food sources.
Lubricant
Saliva cushions the oral mucosa and protects it from trauma when eating, swallowing, and speaking. Food (particularly dry food) adheres to the inside of the mouth in those with low saliva (xerostomia), causing mouth pain.
Digestion
Saliva’s digestive actions include moistening food and aiding in the formation of a meal bolus. Saliva’s lubrication effect permits the food bolus to move easily from the mouth into the oesophagus. Saliva contains the enzyme amylase, also known as ptyalin, which may break down starch into simpler sugars such as maltose and dextrin, which can then be broken down further in the small intestine. The oral cavity is responsible for around 30% of starch digestion. To begin fat breakdown, salivary glands release salivary lipase (a more stronger version of lipase). Salivary lipase is important in fat digestion in newborn infants since pancreatic lipase is still developing.
Role in taste
The sensation of taste relies heavily on saliva. It’s the liquid medium that carries chemicals to taste receptor cells (mostly associated with lingual papillae). Dysgeusia is a condition that affects people who have minimal saliva (i.e. disordered taste, e.g. reduced ability to taste, or having a bad, metallic taste at all times). Saliva Hypernatremia, or excessive quantities of sodium in saliva not caused by any other ailment (e.g., Sjögren syndrome), causes everything to taste “salty.”
Conclusion
Saliva performs protective functions such as buffering, remineralization in healthy oral mucosa, immunological defence, digesting, lubrication, diagnostic purposes, and proteome analysis. Saliva contains enzymes that help digestion and maintain mucosal integrity.