Saliva Secretion

Saliva Secretion

Saliva is secreted by the salivary glands almost 1 to 1.5 liters per day and 1 ml/min.

Saliva play an important role in our body by maintaining health of the oral cavity and carrying functions like mastication, taste, perception, speech etc.

It also act as a systemic status of an individual owing to its ability used for the various diagnostic process in many diseases.

The smallest unit of salivary glands are called secretory unit acini, which are made up of acinar cells which could be serous and mucus.

The serous cells are triangular or pyramidal in shape whereas mucus cells are columnar in shape.

The major acini cells are surrounded by the contractile cells called as myoepithelial cells or basket cells. These basket cells are responsible for the flow of the secretion of saliva by contraction of the cell.

The acini of the salivary glands are connected to the tube like structures called as the ducts.

Parotid gland is having Stensen's duct opens at second molar teeth in buccal mucosa.

Submandibular gland is having Wharton's duct which opens at the sublingual papilla.

Sublingual gland is having Duct of Rivinus which opens at the sublingual fold.



Control of Saliva 

Saliva production is controlled by the autonomic nervous system (ANS).

Quality and quantity of saliva is maintained by the autonomic nervous system.

Autonomic nervous system is comprised of sympathetic and parasympathetic nerve fibers.


Parasympathetic nerve fibers

  • These nerve fibers causes excess release of the saliva in the oral cavity by dilating the ducts and stimulation of the acinar cells of the salivary glands.
  • Parasympathetic nerve fibers stimulates the salivary glands secretes the saliva which contains small quantity of organic components but rich in proteins and produces large amount of Acetylcholine neurotransmitter.

Sympathetic nerve fibers

  • These fibers causes the secretion of the saliva which is rich in organic components and thick mucus.
  • These fibers activate the acinar cells and vasoconstriction of blood vessels which produces thick saliva and rich in Noradrenaline neurotransmitter.



Reflex regulation of Saliva

Saliva is regulated by two types of reflexes -
  1. Unconditioned reflex
  2. Conditioned reflex

Unconditioned reflex 

This is the inborn reflex that does not requires any previous experience. This reflex is activated when anything is placed in the mouth of infants which stimulates the nerve ending present in the mucus membrane of the mouth. 

Conditioned reflex 

This is one that requires the previous experience and does not activates by placing anything in the mouth. It is stimulated by thought of favorite food, smell, hearing, sight.



Hyposalivation

Reduction in the secretion of the saliva is called Hyposalivation.
It is of two types-
  1. Temporary hyposalivation.
  2. Permanent hyposalivation.

Temporary Hyposalivation 

It occurs in-
    • Emotions
    • Fear
    • Stress
    • Psychological problems

Permanent Hyposalivation 

It occurs in-
    • Sialolithiasis- obstruction of salivary duct.
    • Congenital defect in salivary glands.
    • Bells palsy (facial paralysis).


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