Saliva

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Saliva is secreted by the parotid, submandibular, sublingual and buccal salivary glands. The aqueous component is formed by primary secretion of a solution similar to extracellular fluid. This is modified as it passes along the gland ducts, with removal of Na+ and Cl-, and addition of K+ and HCO3-. Bicarbonate makes saliva alkaline and helps buffer the acid in food, protecting against dental caries.

The main organic components of saliva are:

Secretion of saliva is reflexly stimulated via the salivary nuclei in the medulla oblongata in response to:

The efferent limb of the reflex is parasympathetic and follows cranial nerves VII and IX to reach the glands. Parasympathetic stimulation favours a rapid flow of enzyme-rich saliva. Drugs which block parasympathetic neurotransmission produce a dry mouth by inhibiting salivation[1].

There are 3 pairs of glands that are responsible for secreting 90% of saliva:

In total, an average person would secrete around 1.5 litres per day[2].

References

  1. J G Mcgeown et al. 2007, Physiology, Third Edition Master Medicine, Philadelphia PA, Churchill Livingstone Elsevier Limited
  2. Piper M. Treuting, Suzanne M. Dintzis, in Comparative Anatomy and Histology, 2012
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