Physiology of the mouth, pharynx and oesophagus Flashcards
What are the functions of saliva?
Lubricates food for swallowing- helps create bolus. Helps with taste Begins digestion of starch and lipids (alpha amylase, lingual lipase) Protects oral environment: -Washes away bacteria and food particles -Keeps mucosa moist -Cools hot food -Contents destroy bacteria -Maintains alkaline environment- protects teeth
What is the compositon of saliva?
(Hypotonic relative to normal plasma) Water High K+, HCO3- and Ca2+ (relative to plasma) Low Na+ and Cl- (relative to plasma) Mucous Digestive enzymes- alpha amylase lingual lipase Antibacterial agents- thiocynate ions, proteolytic enzymes, antibodies
Why does saliva contain a high concentration of calcium?
Prevents calcium moving out of the teeth down the concentration gradient
What are proteolytic enzymes?
Enzymes that attack bacteria and allow uptake of thiocynate ions which kill bacteria.
What are the 3 pairs of salivary glands? What do they secrete?
Parotid: serous saliva, rich in enzymes, watery Sublingual: mucous saliva, no enzymes Submandibular: mixed serous and mucous
What are Von Ebner’s glands?
Found in the tongue, produce lingual lipase
Describe the structure of salivary glands
Acini: lined by acinar cells, responsible for initial secretion Ducts: lined by duct cells, modify secretions Myoepithelial cells: contractile, eject saliva
Describe the process of primary secretion
Occurs in acinar cells -Isotonic ultrafiltrate from plasma diffuses through acinar cells and mixes with enzymes (serous cells) or mucins (mucous cells) -Secretion drains into ducts
Describe the process of ductal modification
Driven by Na+/K+ ATPase on basolateral membrane of duct cells. Net absorption of Na+ and Cl- and net secretion of K+ and HCO3- Overall net absorption of solute= more concentrated solution Ductal cells are water impermeable, so water cannot follow the solute= hypotonic solution
What is the difference between resting vs stimulated saliva?
At rest saliva flow rate is lower = more time for ductal modification -low volume, highly modified, very hypotonic, neutral pH or slightly acidic, few enzymes At maximal stimulation, flow rate is lower = less time for ductal modification -high volume, less modified, less hypotonic, more alkaline (more bicarb), more enzymes HCO3- is exception= more is secreted with increasing flow rate.
How is saliva secretion controlled?
Parasympathetic: -Increases saliva secretion in response to taste and smell of food, mastication, nausea and conditioned reflexes. -Decreased by sleep, fear and dehydration Sympathetic: -Initially stimulates mucous saliva secretion but then decreases (dry mouth)
Name signs and symptoms of xerostomia
Dry tongue, lips and throat Problems with swallowing and speaking Altered taste Halitosis Oral infections Peridontal disease
What are the causes of xerostomia?
Medication side effects Dehydration Anxiety Sjodren’s syndrome (autoimmune lacrimal gland destruction)
Where are taste buds found?
Tongue (in papillae) Palate Larynx Pharynx
What are the 5 taste classifications?
Sweet Sour Bitter Salty Umami (meaty/savoury taste)
