Saliva - Contents

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
Latin saliva atomaris
Gives rise to molecular saliva
Molecular saliva
Latin saliva molecularis
Precursor atomar saliva
Gives rise to normal saliva
Normal saliva
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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