Saliva
Overview
 
Saliva referred to in various contexts as spit, spittle, drivel, drool, or slobber, is the watery substance produced in the mouth
Mouth
The mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....

s of human
Human
Humans are the only living species in the Homo genus...

s and most other animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

s. Saliva is a component of oral fluid. In mammals, saliva is produced in and secreted from the three pairs of major salivary gland
Salivary gland
The salivary glands in mammals are exocrine glands, glands with ducts, that produce saliva. They also secrete amylase, an enzyme that breaks down starch into maltose...

s, and hundreds of minor salivary glands. Human saliva is composed of 98% water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

, while the other 2% consists of other compounds such as electrolyte
Electrolyte
In chemistry, an electrolyte is any substance containing free ions that make the substance electrically conductive. The most typical electrolyte is an ionic solution, but molten electrolytes and solid electrolytes are also possible....

s, mucus
Mucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...

, blood antibacterial
Antiseptic
Antiseptics are antimicrobial substances that are applied to living tissue/skin to reduce the possibility of infection, sepsis, or putrefaction...

 compounds, and various enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

s.
Encyclopedia
Saliva referred to in various contexts as spit, spittle, drivel, drool, or slobber, is the watery substance produced in the mouth
Mouth
The mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....

s of human
Human
Humans are the only living species in the Homo genus...

s and most other animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

s. Saliva is a component of oral fluid. In mammals, saliva is produced in and secreted from the three pairs of major salivary gland
Salivary gland
The salivary glands in mammals are exocrine glands, glands with ducts, that produce saliva. They also secrete amylase, an enzyme that breaks down starch into maltose...

s, and hundreds of minor salivary glands. Human saliva is composed of 98% water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

, while the other 2% consists of other compounds such as electrolyte
Electrolyte
In chemistry, an electrolyte is any substance containing free ions that make the substance electrically conductive. The most typical electrolyte is an ionic solution, but molten electrolytes and solid electrolytes are also possible....

s, mucus
Mucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...

, blood antibacterial
Antiseptic
Antiseptics are antimicrobial substances that are applied to living tissue/skin to reduce the possibility of infection, sepsis, or putrefaction...

 compounds, and various enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

s. As part of the initial process of food digestion, the enzymes in the saliva break down some of the starch and fat in the food at the molecular level. Saliva also breaks down food caught in the teeth, protecting them from bacteria that cause decay. Furthermore, saliva lubricates and protects the teeth, the tongue, and the tender tissues inside the mouth. Saliva also plays an important role in tasting food, by trapping thiols produced from odorless food compounds by anaerobic bacteria living in the mouth.

Various species have evolved special uses for saliva that go beyond predigestion. Some swift
Swift
The swifts are a family, Apodidae, of highly aerial birds. They are superficially similar to swallows, but are actually not closely related to passerine species at all; swifts are in the separate order Apodiformes, which they share with hummingbirds...

s use their gummy saliva to build nests. Aerodramus
Aerodramus
Aerodramus is a genus of small, dark, cave-nesting birds in the Collocaliini tribe of the swift family. Its members are confined to tropical and subtropical regions in southern Asia, Oceania and northeastern Australia...

nests are prized for use in bird's nest soup
Bird's nest soup
Bird's nest soup is a delicacy in Chinese cuisine. A few species of swift, the cave swifts, are renowned for building the saliva nests used to produce the unique texture of this soup....

. Cobras, vipers, and certain other members of the venom clade hunt with venomous saliva injected by fangs. Some arthropods, such as spiders and caterpillars, create thread from salivary glands.

Digestion

The digestive functions of saliva include moistening food and helping to create a food bolus
Bolus (digestion)
In digestion, a bolus is a mass of food that has been chewed at the point of swallowing. Once a bolus reaches the stomach, digestion begins....

, so it can be swallowed easily. Saliva contains the enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

 amylase
Amylase
Amylase is an enzyme that catalyses the breakdown of starch into sugars. Amylase is present in human saliva, where it begins the chemical process of digestion. Food that contains much starch but little sugar, such as rice and potato, taste slightly sweet as they are chewed because amylase turns...

 (also called ptyalin) that breaks up starch
Starch
Starch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...

 into sugar. This is why the white, popped part of a kernel of popcorn
Popcorn
Popcorn, or popping corn, is corn which expands from the kernel and puffs up when heated. Corn is able to pop because, like sorghum, quinoa and millet, its kernels have a hard moisture-sealed hull and a dense starchy interior. This allows pressure to build inside the kernel until an explosive...

 (which consists of starch) seems to melt on the tongue and taste sweet. Thus, digestion of food begins in the mouth. Salivary glands also secrete salivary lipase (a more potent form of lipase) to start fat digestion. Salivary lipase
Lipase
A lipase is an enzyme that catalyzes the formation or cleavage of fats . Lipases are a subclass of the esterases.Lipases perform essential roles in the digestion, transport and processing of dietary lipids in most, if not all, living organisms...

 plays a large role in fat digestion in newborn infants as their pancreatic lipase still has some time to develop.
It also has a protective function, helping to prevent bacterial build-up on the teeth and washing away adhered food particles.

Disinfectants

A common belief is that saliva contained in the mouth has natural disinfectants
Disinfection
Disinfectants are substances that are applied to non-living objects to destroy microorganisms that are living on the objects. Disinfection does not necessarily kill all microorganisms, especially nonresistant bacterial spores; it is less effective than sterilisation, which is an extreme physical...

, which leads people to believe it is beneficial to "lick their wounds
Wound licking
Wound licking is an instinctive response in humans and many other animals to an injury. Dogs, cats, rodents and primates all lick wounds. The enzyme, lysozyme which is found in many tissues is what is the aid for the wounds. The reason for aid in healing is, lysozyme attacks the cell walls of...

". Researchers at the University of Florida
University of Florida
The University of Florida is an American public land-grant, sea-grant, and space-grant research university located on a campus in Gainesville, Florida. The university traces its historical origins to 1853, and has operated continuously on its present Gainesville campus since September 1906...

 at Gainesville
Gainesville, Florida
Gainesville is the largest city in, and the county seat of, Alachua County, Florida, United States as well as the principal city of the Gainesville, Florida Metropolitan Statistical Area . The preliminary 2010 Census population count for Gainesville is 124,354. Gainesville is home to the sixth...

 have discovered a protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

 called nerve growth factor
Nerve growth factor
Nerve growth factor is a small secreted protein that is important for the growth, maintenance, and survival of certain target neurons . It also functions as a signaling molecule. It is perhaps the prototypical growth factor, in that it is one of the first to be described...

 (NGF) in the saliva of mice
Mouse
A mouse is a small mammal belonging to the order of rodents. The best known mouse species is the common house mouse . It is also a popular pet. In some places, certain kinds of field mice are also common. This rodent is eaten by large birds such as hawks and eagles...

. Wounds doused with NGF healed twice as fast as untreated and unlicked wounds; therefore, saliva can help to heal wounds in some species. NGF has not been found in human saliva; however, researchers find human saliva contains such antibacterial agents as secretory IgA
IGA
Iga or IGA may stand for:-Given name:* a female given name of Polish origin. The name originates from the female given name Jadwiga and stands for gia,or gina in the USA....

, lactoferrin
Lactoferrin
Lactoferrin , also known as lactotransferrin , is a multifunctional protein of the transferrin family. Lactoferrin is a globular glycoprotein with a molecular mass of about 80 kDa that is widely represented in various secretory fluids, such as milk, saliva, tears, and nasal secretions...

, lysozyme
Lysozyme
Lysozyme, also known as muramidase or N-acetylmuramide glycanhydrolase, are glycoside hydrolases, enzymes that damage bacterial cell walls by catalyzing hydrolysis of 1,4-beta-linkages between N-acetylmuramic acid and N-acetyl-D-glucosamine residues in a peptidoglycan and between...

 and peroxidase
Peroxidase
Peroxidases are a large family of enzymes that typically catalyze a reaction of the form:For many of these enzymes the optimal substrate is hydrogen peroxide, but others are more active with organic hydroperoxides such as lipid peroxides...

. It has not been shown that human licking of wounds
Wound licking
Wound licking is an instinctive response in humans and many other animals to an injury. Dogs, cats, rodents and primates all lick wounds. The enzyme, lysozyme which is found in many tissues is what is the aid for the wounds. The reason for aid in healing is, lysozyme attacks the cell walls of...

 disinfects them, but licking is likely to help clean the wound by removing larger contaminants such as dirt and may help to directly remove infective bodies by brushing them away. Therefore, licking would be a way of wiping off pathogens, useful if clean water is not available to the animal or person.

The mouth of animals is the habitat of many bacteria, some pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...

ic. Some diseases, such as herpes, can be transmitted through the mouth. Animal (including human) bites are routinely treated with systemic antibiotics because of the risk of septicemia.

Recent research suggests that the saliva of birds is a better indicator of avian influenza than are faecal samples
Feces
Feces, faeces, or fæces is a waste product from an animal's digestive tract expelled through the anus or cloaca during defecation.-Etymology:...

.

Hormonal function

Saliva secretes Gustin hormone which is thought to play a role in the development of taste buds.

Iodine in salivary glands and oral health

The trophic, antioxidant
Antioxidant
An antioxidant is a molecule capable of inhibiting the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent. Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions. When...

 and apoptosis
Apoptosis
Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...

-inductor actions and the presumed anti-tumour activity of iodide
Iodide
An iodide ion is the ion I−. Compounds with iodine in formal oxidation state −1 are called iodides. This page is for the iodide ion and its salts. For information on organoiodides, see organohalides. In everyday life, iodide is most commonly encountered as a component of iodized salt,...

 might also be important for prevention of oral and salivary glands diseases.

Stimulation

The production of saliva is stimulated both by the sympathetic nervous system
Sympathetic nervous system
The sympathetic nervous system is one of the three parts of the autonomic nervous system, along with the enteric and parasympathetic systems. Its general action is to mobilize the body's nervous system fight-or-flight response...

 and the parasympathetic.

The saliva stimulated by sympathetic innervation is thicker, and saliva stimulated parasympathetically is more watery.

Sympathetic stimulation of saliva is to facilitate respiration, whereas parasympathetic stimulation is to facilitate digestion.

Parasympathetic stimulation leads to acetylcholine (ACh) release onto the salivary acinar cells. ACh binds to muscarinic receptors and causes an increased intracellular calcium ion concentration (through the IP3/DAG second messenger system). Increased calcium causes vesicles within the cells to fuse with the apical cell membrane leading to secretion formation. ACh also causes the salivary gland to release kallikrein
Kallikrein
Kallikreins are a subgroup of serine proteases, enzymes capable of cleaving peptide bonds in proteins. In humans, plasma kallikrein has no known homologue, while tissue kallikrein-related peptidases encode a family of fifteen closely related serine proteases...

, an enzyme that converts kininogen to lysyl-bradykinin. Lysyl-bradykinin acts upons blood vessels and capillaries of the salivary gland to generate vasodilation and increased capillary permeability respectively. The resulting increased blood flow to the acinar allows production of more saliva. Lastly, both parasympathetic and sympathetic nervous stimulation can lead to myoepitheilium contraction which causes the expulsion of secretions from the secretory acinus into the ducts and eventually to the oral cavity.

Saliva production may also be pharmacologically stimulated by so called sialagogue
Sialagogue
A herb with sialagogue action stimulates the secretion of saliva from the salivary glands.Herbs with sialagogue action include:*Bloodroot *Blue Flag *Cayenne pepper...

s. It can also be suppressed by so called antisialagogue
Antisialagogue
Antisialagogues are substances that decrease the production of saliva and their effect is opposite to that of sialagogues. Their origin may be both natural and synthetic. Classic antisialagogues:* atropine,* opium,* alkalies,* belladonna,* hyoscyamus,...

s.

Daily salivary output

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
Submandibular gland
The paired submandibular glands are salivary glands located beneath the floor of the mouth. In humans, they account for 70% of the salivary volume and weigh about 15 grams. Unstimulated in humans, the percentage contribution to whole saliva; ~25% Parotid, Submandibular and Sublingual ~ 67% and...

 contributes around 70–75% of secretion, while the parotid gland
Parotid gland
The paired parotid glands are the largest of the salivary glands. They are each found wrapped around the mandibular ramus, and secrete saliva through Stensen's ducts into the oral cavity, to facilitate mastication and swallowing and to begin the digestion of starches.-Location:The parotid glands...

 secretes about 20–25 % and small amounts are secreted from the other salivary glands.

Contents

Produced in salivary gland
Salivary gland
The salivary glands in mammals are exocrine glands, glands with ducts, that produce saliva. They also secrete amylase, an enzyme that breaks down starch into maltose...

s, human saliva is 98% water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

, but it contains many important substances, including electrolyte
Electrolyte
In chemistry, an electrolyte is any substance containing free ions that make the substance electrically conductive. The most typical electrolyte is an ionic solution, but molten electrolytes and solid electrolytes are also possible....

s, mucus
Mucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...

, antibacterial
Antiseptic
Antiseptics are antimicrobial substances that are applied to living tissue/skin to reduce the possibility of infection, sepsis, or putrefaction...

 compounds and various enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

s.

It is a fluid
Fluid
In physics, a fluid is a substance that continually deforms under an applied shear stress. Fluids are a subset of the phases of matter and include liquids, gases, plasmas and, to some extent, plastic solids....

 containing:
  • Water
    Water
    Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

  • Electrolyte
    Electrolyte
    In chemistry, an electrolyte is any substance containing free ions that make the substance electrically conductive. The most typical electrolyte is an ionic solution, but molten electrolytes and solid electrolytes are also possible....

    s:
    • 2–21 mmol/L sodium
      Sodium
      Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

       (lower than blood plasma
      Blood plasma
      Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...

      )
    • 10–36 mmol/L potassium
      Potassium
      Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...

       (higher than plasma)
    • 1.2–2.8 mmol/L calcium
      Calcium
      Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

       (similar to plasma)
    • 0.08–0.5 mmol/L magnesium
      Magnesium
      Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...

    • 5–40 mmol/L chloride
      Chloride
      The chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...

       (lower than plasma)
    • 25 mmol/L bicarbonate
      Bicarbonate
      In inorganic chemistry, bicarbonate is an intermediate form in the deprotonation of carbonic acid...

       (higher than plasma)
    • 1.4–39 mmol/L phosphate
      Phosphate
      A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...

    • Iodine
      Iodine
      Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....

       (mmol/L usually higher than plasma, but dependent variable according to dietary iodine intake)
  • Mucus
    Mucus
    In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...

    . Mucus in saliva mainly consists of mucopolysaccharides
    Glycosaminoglycan
    Glycosaminoglycans or mucopolysaccharides are long unbranched polysaccharides consisting of a repeating disaccharide unit. The repeating unit consists of a hexose or a hexuronic acid, linked to a hexosamine .-Production:Protein cores made in the rough endoplasmic reticulum are posttranslationally...

     and glycoprotein
    Glycoprotein
    Glycoproteins are proteins that contain oligosaccharide chains covalently attached to polypeptide side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycosylation. In proteins that have segments extending...

    s;
  • Antibacterial compounds (thiocyanate
    Thiocyanate
    Thiocyanate is the anion [SCN]−. It is the conjugate base of thiocyanic acid. Common derivatives include the colourless salts potassium thiocyanate and sodium thiocyanate. Organic compounds containing the functional group SCN are also called thiocyanates...

    , hydrogen peroxide
    Hydrogen peroxide
    Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...

    , and secretory immunoglobulin A
    Immunoglobulin A
    Immunoglobulin A is an antibody that plays a critical role in mucosal immunity. More IgA is produced in mucosal linings than all other types of antibody combined; between three and five grams are secreted into the intestinal lumen each day....

    )
  • Epidermal growth factor
    Epidermal growth factor
    Epidermal growth factor or EGF is a growth factor that plays an important role in the regulation of cell growth, proliferation, and differentiation by binding to its receptor EGFR...

     or EGF
    EGF
    EGF can refer to several things:*Epidermal growth factor, a growth factor in biology*Exponential generating function, a function in mathematics*European Gendarmerie Force, a European intervention force...

  • Various enzyme
    Enzyme
    Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

    s. There are three major enzymes found in saliva.
    • α-amylase
      Amylase
      Amylase is an enzyme that catalyses the breakdown of starch into sugars. Amylase is present in human saliva, where it begins the chemical process of digestion. Food that contains much starch but little sugar, such as rice and potato, taste slightly sweet as they are chewed because amylase turns...

       (EC3.2.1.1). Amylase starts the digestion of starch and lipase fat before the food is even swallowed. It has a pH
      PH
      In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

       optima of 7.4.
    • lingual lipase
      Lingual lipase
      Lingual lipase is a member of a family of digestive enzymes called lipases, EC 3.1.1.3, that use the catalytic triad of Aspartate , Histidine , and Serine to hydrolyze long-chain triglycerides into partial glycerides and free fatty acids. The enzyme catalyzes the first reaction in the digestion of...

      . Lingual lipase has a pH
      PH
      In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

       optimum ~4.0 so it is not activated until entering the acidic environment of the stomach.
    • Antimicrobial
      Antimicrobial
      An anti-microbial is a substance that kills or inhibits the growth of microorganisms such as bacteria, fungi, or protozoans. Antimicrobial drugs either kill microbes or prevent the growth of microbes...

       enzymes that kill bacteria.
      • Lysozyme
        Lysozyme
        Lysozyme, also known as muramidase or N-acetylmuramide glycanhydrolase, are glycoside hydrolases, enzymes that damage bacterial cell walls by catalyzing hydrolysis of 1,4-beta-linkages between N-acetylmuramic acid and N-acetyl-D-glucosamine residues in a peptidoglycan and between...

      • Salivary lactoperoxidase
        Lactoperoxidase
        Lactoperoxidase is a peroxidase enzyme secreted from mammary, salivary, and other mucosal glands that functions as a natural antibacterial agent. Lactoperoxidase is a member of the heme peroxidase family of enzymes. In humans, lactoperoxidase is encoded by the LPO gene.Lactoperoxidase catalyzes...

      • Lactoferrin
        Lactoferrin
        Lactoferrin , also known as lactotransferrin , is a multifunctional protein of the transferrin family. Lactoferrin is a globular glycoprotein with a molecular mass of about 80 kDa that is widely represented in various secretory fluids, such as milk, saliva, tears, and nasal secretions...

      • Immunoglobulin A
        Immunoglobulin A
        Immunoglobulin A is an antibody that plays a critical role in mucosal immunity. More IgA is produced in mucosal linings than all other types of antibody combined; between three and five grams are secreted into the intestinal lumen each day....

    • Proline
      Proline
      Proline is an α-amino acid, one of the twenty DNA-encoded amino acids. Its codons are CCU, CCC, CCA, and CCG. It is not an essential amino acid, which means that the human body can synthesize it. It is unique among the 20 protein-forming amino acids in that the α-amino group is secondary...

      -rich proteins (function in enamel
      Tooth enamel
      Tooth enamel, along with dentin, cementum, and dental pulp is one of the four major tissues that make up the tooth in vertebrates. It is the hardest and most highly mineralized substance in the human body. Tooth enamel is also found in the dermal denticles of sharks...

       formation, Ca2+-binding, microbe killing and lubrication)
    • Minor enzymes include salivary acid phosphatase
      Acid phosphatase
      Acid phosphatase is a phosphatase, a type of enzyme, used to free attached phosphate groups from other molecules during digestion. It is basically a phosphomonoesterase...

      s A+B, N-acetylmuramoyl-L-alanine amidase
      N-acetylmuramoyl-L-alanine amidase
      In enzymology, a N-acetylmuramoyl-L-alanine amidase is an enzyme that catalyzes a chemical reaction that cleaves the link between N-acetylmuramoyl residues and L-amino acid residues in certain cell-wall glycopeptides....

      , NAD(P)H dehydrogenase (quinone)
      NAD(P)H dehydrogenase (quinone)
      In enzymology, a NADH dehydrogenase is an enzyme that catalyzes the chemical reactionThe 4 substrates of this enzyme are NADH, NADPH, H+, and quinone, whereas its 3 products are NAD+, NADP+, and hydroquinone....

      , superoxide dismutase
      Superoxide dismutase
      Superoxide dismutases are a class of enzymes that catalyze the dismutation of superoxide into oxygen and hydrogen peroxide. As such, they are an important antioxidant defense in nearly all cells exposed to oxygen...

      , glutathione transferase, class 3 aldehyde dehydrogenase
      Aldehyde dehydrogenase
      Aldehyde dehydrogenases are a group of enzymes that catalyse the oxidation of aldehydes.- Function :Aldehyde dehydrogenase is a polymorphic enzyme responsible for the oxidation of aldehydes to carboxylic acids, which leave the liver and are metabolized by the body’s muscle and heart...

      , glucose-6-phosphate isomerase
      Glucose-6-phosphate isomerase
      -Other functions:There is evidence that phosphoglucose isomerase acts as a molecular messenger. It is produced and secreted by white blood cells, and acts to regulate the growth of several different cell types.-Pathology:...

      , and tissue kallikrein
      Kallikrein
      Kallikreins are a subgroup of serine proteases, enzymes capable of cleaving peptide bonds in proteins. In humans, plasma kallikrein has no known homologue, while tissue kallikrein-related peptidases encode a family of fifteen closely related serine proteases...

       (function unknown).
  • Cells: Possibly as much as 8 million human 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
    Halitosis
    Halitosis is a term used to describe noticeably unpleasant odors exhaled in breathing. Halitosis is estimated to be the third most frequent reason for seeking dental aid, following tooth decay and periodontal disease.- General :...

    .
  • Opiorphin
    Opiorphin
    Opiorphin is an endogenous chemical compound first isolated from human saliva. Initial research with mice shows the compound has a painkilling effect greater than that of morphine. It works by stopping the normal breakdown of enkephalins, natural pain-killing opioids in the spinal cord...

    , a newly researched pain-killing substance found in human saliva.

Spitting of saliva

Spitting
Spitting
Spitting or expectoration is the act of forcibly ejecting saliva or other substances from the mouth. It is currently considered rude and a social taboo in many parts of the world including the West, while in some other parts of the world it is considered more acceptable...

 or expectoration is the act of forcibly ejecting saliva or other substances from the mouth. It is often considered rude and a social taboo
Taboo
A taboo is a strong social prohibition relating to any area of human activity or social custom that is sacred and or forbidden based on moral judgment, religious beliefs and or scientific consensus. Breaking the taboo is usually considered objectionable or abhorrent by society...

in many parts of the world, including the West – where it is frequently forbidden by local laws, because it was thought to facilitate the spread of disease; the laws are generally not strictly enforced. In some other parts of the world, expectoration is more acceptable.
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