Contents
Produced in salivary glands, human saliva is 99.5% water, but it contains many important substances, including electrolytes, mucus, antibacterial compounds and various enzymes.
Atomar saliva | |
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Latin | saliva atomaris |
Gives rise to | molecular saliva |
Molecular saliva | |
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Latin | saliva molecularis |
Precursor | atomar saliva |
Gives rise to | normal saliva |
Normal saliva | |
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Latin | saliva normalis |
Precursor | molecular saliva |
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 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 or EGF
- Various enzymes. There are three major enzymes found in saliva.
- α-amylase (EC3.2.1.1). α-Amylase, 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 optima of 7.4.
- Lingual lipase. Lingual lipase, which is secreted by the acinar cells of the sublingual gland, has a pH optimum ~4.0 so it is not activated until entering the acidic environment of the stomach.
- Kallikrein. Kallikrein is 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)
- Minor enzymes include 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 (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.
- Opiorphin, a newly researched pain-killing substance found in human saliva.
Read more about this topic: Saliva
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