Oral physiology Flashcards
Structure of acinus
12+ Acinar cells around a central lumen. Zygomen granules (digestive enzymes) Mucus cells (downstream of acinar cells) Myoepithelial cells to contract and squeeze stuff into the main duct.
Types of ducts (salivary glands)
Intercalated, striated, excretory
The rate of flow vs composition
Increased flow = increased conc of NaCl and HCO3
Movement of substances from blood to the lumen of the acinus
Na+ to the lumen through tight junctions.
Cl- and HCO3- from blood to acinus via co-transporters e.g. transcellular.
Primary saliva is isotonic
Modification of primary secretion
In the duct.
Reabsorption of NaCl
Secretion of K+ and bicarbonate (= high pH).
Ductal cells impermeable to water so final saliva is hypertonic.
What is oral mucosa
The soft tissue of the mouth
What is oral mucosa composed of
Stratified squamous epithelium
What’s the function of oral mucosa
Barrier to bacteria and mechanical irritation and protects against dryness.
The different classifications of oral mucosa
Masticatory mucosa, lining mucosa and specialized mucosa
Lining mucosa properties
Can be stretched, compressed and is moist.
Location of lining mucosa
Buccal surfaces, Ventral surface of tongue, Floor of mouth, Labial Alveolar mucosa, Soft palate.
Histology of lining mucosa
Non-keratinised SSE
Elastic fibres in lamina propria and sub-mucosa = a movable base.
Fordyce spots/granules (misplaces sebaceous glands usually associated w hair follicles)
Masticatory mucosa locations
Attached gingiva, hard palate, dorsal surface of tongue
Transduction mechanism for Umami tastant
G-coupled protein receptor.
T1Rs = T1R2, T1R3
Transduction mechanism for Sweet tastant
G -coupled protein receptor
T1R1, T1R3
Transduction mechanism for Salt tastant
Ion channel = NaCl, KCl (inorganic salts)
Transduction mechanism for Sour tastant
Ion channel = H+
Transduction mechanism for Bitter tastant
G-coupled protein receptor.
TR2’s
Which tastant are we most sensitive to.
Bitter
Sour produces most saliva bc needs to buffer the H+
Mechanism of AP from eating food
- Chewing the food = mechanical and chemical stimulation so saliva released.
- Molecules from broken down food dissolve in saliva and enter taste pore.
- Molecules interact with Ion channels/protein receptors.
- Ca2+ released from stores so increase in conc.
- Increase in [Ca] = exocytosis of transmitters.
6 = AP
Factors affecting taste
Genetics Saliva composition, quantity, etc. Disease Past experience Olfaction Adaption
Structure of acinar/secretory system
~12 acinar cells (serous) around an intercalated duct
Mucous cells further downstream
+Zygome granules
+myoepithelial cells to squeeze saliva downstream
Intercalated then striated then excretory duct.
Movement of substances from blood to the lumen of the acinus
Na+ and water travel straight through.
Na+/K+ enter basolateral membrane, Na+/Cl- exchanged (Cl- in)
HCO3, K+, and Cl- exit to the lumen at luminal membrane.
Movement of substances from the lumen of the duct to blood
Luminal membrane: H+/K+ exchanger (H+ in), H+/Na+ exchanger (H+ out), HCO3/Cl- exchanger (Cl- in).
Basolateral membrane/to blood: K+ moves into the duct, Na+ and Cl- move out.
Impermeable to water.
Stephan’s Curve: Rate of drop of pH due to ?
- Metabolic activity of plaque microbes.
2. Complexity/type of substrate
Stephan’s Curve: pH reached depends on?
- Type of bacteria e.g. acidogenic = lower pH
- The complexity of the carbs
- The rate of diffusion e.g. affected by plaque thickness, clearing rate of saliva, etc.
Stephan’s Curve: Time taken for normal pH to return
- The activity of bacteria inhibited by low pH
- Saliva flow and composition
- Plaque/rate of diffusion.
What is the critical pH
pH where CaPO4 crystals dissolve.
= 1/[Ca] or [PO4]
Benefits of the enamel pellicle
Physical barrier e.g. against abrasion Barrier against bacteria Neutralises bacterial acids Reduces demineralization Inhibits calculus growth
Properties of parasympathetic saliva
A Larger volume as it’s more watery (serous)
Secreted via Ach pathways.
Properties of sympathetic saliva
Smaller volume but rich in mucins so feels thick
Via noradrenaline pathways
Problems caused by xerostomia
Difficulty/pain eating, swallowing, speaking
More gingival infections/tooth decay/poor oral health
Diminished taste
Advantages of the structure of salivary glands
- The epithelium of luminal membrane can be accessed non-invasively
- Well encapsulated = less spread of vectors.
- Non-vital e.g. can be removed.
- Cells are well differentiated and slow dividing = a stable population.
Types of acini
Serous, mucous, mixed
Serous Acini
Dark staining
Nucleus in basal third
Secrete a-amylase and water rich saliva to digest starch.
Small central duct
Mucous acini
Light foamy stained appearance.
Nucleus at base
Large central duct
Secretes mucins (glycoproteins) and water for lubrication
Composition of primary saliva
Isotonic, NaCl rich plasma like fluid
What does whole saliva contain
Acinar secretions/saliva Blood Cell fragments Microorganisms Food remnants Electrolytes Mucins Antibacterials e.g. lysozyme Enzymes
Role/structure of intercalated ducts
Cuboidal cells
Secretory duct e.g. connects acini to the larger striated ducts.
Role/structure of striated ducts
Basal membrane highly folded into microvilli = more surface area for active transport.
NaCl absorbed, HCO3 and K+ secreted.
Impermeable to water so resulting saliva is hypotonic.
Rich in mitochondria due to all the active transport.
Name 5 salivary glands
Parotid Sub-mandibular Sub-lingual Von-Ebner Weber's
Parotid gland secretions
Serous secretions.
Stenson’s duct (crosses masseter and pierces buccinator before entering the oral cavity)
Von-Ebner’s glands
Minor salivary glands Serous secretions (the only minor salivary gland not mucus). Found at the base of tongue, underlying the circumvallate papillae.
Weber’s glands
Mucous secretions
Found in tonsils.
Types of damage to salivary glands
Obstructive, degenerative, infectious, drug side-effects
Types of damage to salivary glands: Obstructive
E.g. calculus stones blocking the ducts
Types of damage to salivary glands: Degenerative
E.g. after radiotherapy or due to Sjogren’s syndrome (affects post-menopausal women and their glands)
Types of damage to salivary glands: inflammatory
Infection, swelling
Types of damage to salivary glands: Drug side-effects
Affect the Ach or noradrenaline pathways
What do acinar cells also secrete
Electrolytes IgA/IgG Mucins Cystatins Histatines Statherins Enzymes e.g a-amylase or lipase Antimicrobial proteins
What are the functions of Statherins, Histatines, and Cystatins in saliva?
All of a mineralization function.
Histatines = buffer
Cystatins = tissue coating
Statherins = Lubrications and vasoelasticity
Sub-mandibular
Unstimulated saliva mostly from here.
Mixed e.g. mucous and serous
Wharton’s duct
Deep and superficial lobes separated by posterior surface of mylohyoid muscle.
Sub-lingual
Mostly mucous
Joins Wharton’s duct and has some small ducts that go directly to the mouth.
What affects saliva composition/amount
Age Time of day Gender Diet Drugs Gland size/type Stimulation type and duration Circadian rhythm (24h cycle) Flow rate
the role of saliva
Lubrication and tissue coating A solvent for taste Digestive Defensive Immunity (antibacterials/antifungal/etc) Buffering Remineralisation Mechanical cleaning Needed to hold dentures in place
How can we determine the composition of saliva
2D/1D electrophoresis
functions of salivary proteins
Taste and digestion
Lubrication - mucins
Immunity/defensive - IgA, IgG, lysozymes
Host protective features during periodontal disease/gingivitis
A complete layer of epithelium = physical barrier
Saliva flow and contains neutrophils/innate immunity
Crevicular fluid increases and contains neutrophils etc = innate immunity.
For periodontitis, phagocytes etc activated (active immunity)
Histological features of Gingivitis
Dilated capillaries = red and bleeding gums
Inflammatory cells
Leaking crevicular fluid (containing neutrophils)
No migration of junctional epithelium
No bone loss
Clinical features of gingivitis
False pocketing
Bleeding
Histological features of periodontal disease
Migration of jucntional epithelium
Bone loss = wobbly teeth or drifitng teeth
True pocketing (7mm)
Ulceration and bleeding gums
Chronic inflammation = plasma cells, lymphocytes
Clinical features of periodontal disease
True pocketing (7mm)
Bone loss - can be checked using a bitewing x-ray
Bleeding
Accumulation of calculus
The appearance of healthy gingiva
Pale pink
Firm and stippled
Knife edge gingival margin
The appearance of gums w periodontal disease
Red, inflamed and bleeding
Lost the stippled appearance
Rolled gingival margins
Types of gingival disease
Hereditary or acquired. Plaque-induced or not. Infective e.g. herpes. Affected by systemic illnesses etc e.g. pregnancy or diabetes. Inflammatory or not hyper or hypoplastic. Allergic Traumatic
Chronic periodontitis features
Localised or generalized (>30%)
Bad bacteria > good bacteria
Affected by systemic factors e.g. smoking, stress, plaque levels, diabetes.
Progressive bone/attachment loss consistent w local factors
Acute periodontitis
Aggressive and rapid bone/attachment loss, not consistent w local factors.
The patient appears to be healthy.
Localised or generalized.
Macrophage/neutrophil abnormalities.
Steps needed in a treatment plan
- Care of the pain
- Prevention (finding and stopping the cause)
- Stabilisation
- Rehabilitation
- Maintenance.
Why do systemic illnesses affect oral health
Affect the saliva.
Affect host responses e.g. inflammatory response, antibodies/neutrophils etc.
Affects strength of the tissues e.g. how easily they get infected etc.
Changes in epithelium
Atrophy Hyperplasia Hyperkeratinised Ulcers/loss of epithelium When epithelium separates from underlying CT
Atrophy of oral epithelium
Red fragile epithelium
When rate of loss of cells > rate of new cell production
Reasons = immune mediated, vitamin B12 deficiency, age.