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Questions and Answers
What is the primary function of secretion from the parotid gland?
Which nerve is associated with the parasympathetic supply to the parotid gland?
Which of the following acts as a cotransmitter with acetylcholine in some postganglionic parasympathetic neurons?
What role do buffers in saliva play regarding oral health?
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Which of the following stimuli can trigger the secretion of saliva as an unconditioned reflex?
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What is the consequence of atropine or other cholinergic blocking agents on salivary secretion?
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Which component of saliva is important for neutralizing acidic conditions in the mouth?
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Which kind of secretion is characterized by a secretion of a small amount of saliva rich in organic constituents?
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Which type of secretion is primarily secreted by the parotid glands?
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What percentage of saliva is secreted by submandibular glands?
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What is the primary composition of saliva?
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How is salivary secretion primarily controlled?
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What happens during the secondary stage of salivary secretion in the ducts?
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What ion is actively reabsorbed in the salivary ducts, resulting in lower concentrations in the saliva?
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Which cells in the acini secrete the primary secretion containing the enzyme ptyalin?
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What type of innervation do salivary glands receive primarily from the parasympathetic nervous system?
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Study Notes
Salivary Glands
- Three pairs of glands produce saliva: parotid, submandibular, and sublingual glands.
- There are also buccal glands.
- The glands contain acini that secrete a primary secretion
- Serous cells in the acini secrete a watery solution that contains ptyalin (α amylase enzyme)
- Mucous cells in acini secrete a viscous solution containing mucin
- Salivary ducts open into the oral cavity.
Types of Salivary Glands
- Parotid glands acini are serous and make up 25% of saliva.
- Sublingual glands acini are mucous and make up 5% of saliva.
- Submandibular glands acini are mixed and make up 70% of saliva.
- Buccal glands secrete only mucous.
Salivary Secretion
- Saliva volume is ~ 1500 ml per day
- Resting saliva pH is approximately 7.0.
- Saliva contains:
- Proteins: ptyalin (enzyme) and mucin (protein)
- Electrolytes: K+, HCO3-, Na+, Cl-
- Saliva is hypotonic.
- Aldosterone plays a role in electrolyte balance.
- Salivary secretion is regulated by the autonomic nervous system (ANS).
Mechanism of Secretion
- Primary secretion occurs in the acini and contains ptyalin/mucin in solution.
- Secondary secretion takes place in the salivary ducts.
- Na+ is actively reabsorbed in the ducts, while K+ is simultaneously actively secreted.
- Na+ reabsorption is greater than K+ secretion.
- Cl- is passively reabsorbed.
- Na+ and Cl- concentrations are reduced, while K+ concentration increases within salivary ducts.
- HCO3- is actively secreted into duct lumen
- Ducts are mostly impermeable to water which makes saliva hypotonic.
Innervation
- Salivary glands are innervated by both parasympathetic and sympathetic fibers.
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Parasympathetic fibers originate from:
- Superior salivary nucleus (medulla) for sublingual and submaxillary glands.
- Inferior salivary nucleus (medulla) for the parotid gland.
- Sympathetic fibers originate from the lateral horn of the first and second thoracic segments.
Parasympathetic Innervation
-
Sublingual and submaxillary glands:
- Chorda Tympani (facial nerve)
- Submandibular ganglion.
-
Parotid gland:
- Glossopharyngeal nerve
- Otic ganglion.
Sympathetic Innervation
- Origin: lateral horn cells of the first and second thoracic segments.
- Relay: superior cervical ganglion.
- Postganglionic fibers supply all salivary glands.
Functional Differences
-
Parasympathetic stimulation:
- Profuse watery saliva secretion.
- High electrolyte content with relatively low organic material.
- Marked vasodilation caused by vasoactive intestinal peptide (VIP).
-
Sympathetic stimulation:
- Vasoconstriction.
- Secretion of small amount of saliva rich in organic material.
- VIP is a cotransmitter with acetylcholine in some postganglionic parasympathetic neurons.
Control of Salivary Secretion
- Salivary secretion is influenced by:
- Conditioned reflexes: sights, smells, sounds, and thoughts of food.
- Unconditioned reflex: presence of food in the mouth (taste, touch, temperature).
- The appetite area in the hypothalamus receives signals from the taste and smell areas of the cerebral cortex.
Functions of Saliva
-
Protection of oral mucosa:
- Cooling hot foods
- Neutralizing acids: saliva buffers maintain a pH of approximately 7.0.
- Maintaining oral hygiene:
- Washing away bacteria and food remnants.
- Lysozyme attacks bacterial walls.
- Antibodies (IgA) destroy pathogens
- Lactoferrin has bacteriostatic effects
-
Teeth Protection:
- Buffers in saliva maintain oral pH at ~7.0. This pH prevents teeth from losing calcium which leads to dental caries.
- Fluoride protects tooth enamel.
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Description
Explore the structure and function of the salivary glands in this quiz. Discover details about the parotid, submandibular, and sublingual glands, as well as their secretion processes and compositions. Test your knowledge on saliva's role in digestion and its physiological properties.