Introduction

  • The nervous system controls salivary secretion. The smell or taste of food, and masticatory stimuli affect the amount of salivary secretion. Secretion of saliva can be divided into two phases – the primary phase which involves secretory acini, and the secondary phase which occurs in excretory ducts.

You can read more about the classification and composition of saliva here.

Saliva – Neural Control

  • The autonomic nervous system affects the composition and flow of saliva from glands.
  • Parasympathetic Nerves:
    • Primary control of salivary glands is through parasympathetic nerves. These nerves are responsible for secretion of watery, electrolyte-rich and low protein saliva.
    • The parotid gland is primarily stimulated and partly the submandibular gland. Hence, while eating, serous salivary secretion is stimulated.
    • The most effective stimulus for an increase in salivary secretion is a sour taste followed by a salty taste.
  • Sympathetic Nerves:
    • In situations of fear, anger, stress, or vigorous exercise where sympathetic nerves are stimulated, the salivary glands produce thicker, protein-rich saliva. This occurs due to a modification in vascular supply of gland by the sympathetic nerves.
    • The sublingual gland and partly the submandibular gland are responsible for an increase in mucous content of salivary secretion.

Salivary Reflex

  • Unconditioned reflex: It is an inborn reflex, which induces secretion of saliva when any substance is placed in oral cavity.
  • Conditioned reflex: It is a reflex acquired by experience. Even a thought of your favourite food initiates salivary secretion. 

Physiological Process of Formation:

  • Primary secretory phase:
    • Formation of protein component:
Formation of Protein Component in Saliva- Flow Diagram
Formation of Protein Component – Flow Diagram
    • Formation of electrolyte component:
Formation of electrolyte component in saliva - flow diagram
Formation of electrolyte component – flow diagram
  • Secondary/Modification phase of secretion
    • Saliva produced by secretory acini contain electrolytes such as sodium and chloride. Prevention the loss of sodium and chloride ions from the body is necessary. The excretory ducts play a key role in reabsorbing sodium and chloride secreted in saliva from acini. Thus, the end product is hypotonic to plasma.
    • The striated duct modifies secreted saliva from acini by reabsorbing sodium and chloride ions and simultaneously excreting potassium and bicarbonate ions.
    • The autonomic nervous system and mineralocorticoids control the modification step.

Summary

  • Salivary secretion is controlled by both the parasympathetic and sympathetic nervous systems.
  • The parasympathetic system is typically responsible in normal day-to-day function.
  • The sympathetic system usually works when our ‘fight or flight’ response is triggered.
  • Saliva can be divided in to a protein component and an electrolyte component. These vary in composition based on the nervous system controlling production.
  • Further modification of the saliva occurs in the ducts.

Recommended Reading

References
  1. Kumar GS (2015) Orban’s Oral histology and embryology. 14th edn: Elsevier India.
  2. Sembulingum K and Sembulingum P (2012) Essentials of medical physiology 6th edn: Jaypee publications.

How useful was this post?

Click on a star to rate it!

Average rating / 5. Vote count:

No votes so far! Be the first to rate this post.

As you found this post useful...

Follow us on social media!

We are sorry that this post was not useful for you!

Let us improve this post!

LEAVE A REPLY

Please enter your comment!
Please enter your name here