Oral environment 1 Flashcards
Components of oral fluid
saliva, gingival crevicular fluid, oral bacteria, food debris, epithelial cells
2 overall functions of oral fluid
protection and digestion
Examples of the protective function of oral fluids
buffering, antimicrobial, remineralisation, cleansing, mucosal protection
Examples of the digestive function of oral fluids
taste, digestive enzymes, bolus lubrication for mastication and deglutination
What is a prominent symptom for patients with salivary gland disease?
xerostomia (dry mouth)
Effects of reduced salivary flow
increased incidence of caries
Which tooth surfaces are most at risk of caries due to reduced salivary flow?
Buccal and labial
What type of glands are salivary glands?
Exocrine
Structure of salivary glands
compound, tubulo-acinar glands
What are the major (paired) salivary glands
parotid, submandibular, sublingual
Where are the minor salivary glands located?
Buccal, labial, lingual, palatal (cheeks, lips, tongue, palate)
Which histological layer are minor salivary glands found in?
(glandular tissue found in) lamina propria
Names of different ducts found in salivary glands
Intercalated ducts emerge from the acini and join to into the striated duct. Striated ducts from multiple bundles of acini join into the single collecting duct.
Microscopic appearance of serous acini
Stain pink with H+E, rounded nuclei which are more centrally located in each cell
Microscopic appearance of mucous acini
foamy cytoplasm, flattened, peripherally-located nuclei (full of vesicles containing mucin)
Microscopic appearance of mixed acini
mucous and serous acini can be seen
Type of secretion from parotid gland
serous
type of secretion from submandibular gland
seromucous
Type of secretion from sublingual gland
mucous
Type of secretions from minor salivary glands
Buccal, labial, palatal minor salivary glands all have mucous secretions. Lingual salivary glands secrete serous and mucous secretions (but the acini are not mixed)
Name of fluid lining the gingival sulcus/crevice
Gingival crevicular fluid (GCF)
What will cause an increase in gingival crevicular fluid (GCF)?
Inflammation (e.g. gingivitis) - GCF is probably an inflammatory exudate
Name of the epithelium in the gingival sulcus/crevice
sulcular/crevicular epithelium
Name of the epithelium that attaches to the tooth
junctional epithelium
What is the rate of salivary flow when sleeping?
0.03 ml/min
What is the salivary flow rate when resting but awake?
0.3 ml/min
What is the salivary flow rate when eating?
3.0 ml/min
Average total salivary flow
620 ml
% contributions of the salivary glands when asleep
submandibular 70%
sublingual 15%
Minor glands 15%
parotid 0%
% contributions of salivary glands when awake but resting
submandibular 72%
parotid 20%
sublingual 4%
minor glands 4%
% contributions of salivary glands when stimulated (eating)
Parotid 50%
Submandibular 40%
Minor glands 8%
Sublingual 2%
Factors that affect unstimulated salivary flow rate
hydration, previous stimulation, circannual rhythms (seasons), medications, salivary gland disease
Composition of saliva
inorganic - water (99.5%) and ions (0.2%)
organic - proteins (0.3%), very little carbohydrate or lipid
As salivary flow rate increases, how does the composition of ions change in saliva?
Na+, Cl- and HCO3- concentrations increase, K+ concentration decreases
Why do Na+ and Cl- concentrations in saliva increase as flow rate increases?
Na+ and Cl- are the driving forces for salivary secretion (water follows by osmosis)
Significance of increased HCO3- concentration at higher flow rates
HCO3- is an effective buffer of plaque acids around pH 7 (important when eating)
Which ions are present in saliva?
Fluoride, calcium, phosphate, thiocyanate, bicarbonate, (sodium, chloride, potassium)
Function of fluoride in saliva
Forms fluorapatite, antibacterial (acts on H pump), promotes remineralisation
Function of calcium and phosphate ions in saliva
remineralisation (also phosphate is a buffer)
Function of thiocyanate (SCN) in saliva
antibacterial
function of bicarbonate and phosphate in saliva
buffer
List of salivary buffers
bicarbonate, phosphates, proteins, bacterial NH3
When is bicarbonate most effective as a buffer?
At high salivary flow rates when HCO3- concentration is greatest
When are phosphates most effective at buffering?
At rest, near pH 7
When are proteins most effective at buffering?
Limited due to main buffering occurring at pH<5
How is NH3 produced?
By bacteria: urea -> CO2 + NH3 catalysed by urease
How is saliva secreted?
Na+ is able to move by facilitated diffusion from the blood into the intercalated duct via acini cells. Cl- moves into the acini cells via Cl-/K+ pump. ACh causes depolarisation of the acini cells which triggers the release of Ca2+. Ca2+ bind to Cl- receptors opening them so Cl- can diffuse into the duct. Water follows Na+ and Cl- into the duct lumen.
Equation for phosphate buffer
H2PO4 - <-> H+ + HPO4 2-
How does NH3 act as a buffer?
NH3 + H+ -> NH4+
