Oral environment 2 Flashcards
Function of amylase
Enzyme that hydrolyses alpha 1,4- glycosidic bonds in starch to maltose. Potential defence role
Which ion is required for amylase secretion?
Ca2+
Which ion is a cofactor for amylase?
Cl- (activates amylase)
Where is amylase present?
Most mucosal gland secretions (including tears - defence role)
Why is starch cariogenic?
Starch is broken down into maltose which can be used by bacterial to lower pH of dental plaque causing caries.
Which is the most cariogenic sugar?
Sucrose
Alternative name for lysozyme
muramidase
Function of lysozyme / muramidase
ubiquitous non-specific defence role. Attacks bonds in bacterial cell walls causing lysis (antibacterial)
Where is lysozyme / muramidase present?
many secretions e.g. tears, saliva, vaginal mucus
Function of lactoperoxidase / sialoperoxidase
catalyses the reaction of 2 H2O2 -> 2 H2O + O2 which enables the oxidation of SCN- (thiocyanide) to OSCN- (hypothiocyanate) which has an antibacterial role.
Where is lactoperoxidase / sialoperoxidase secreted from?
salivary glands and some bacteria
Function of cystatins
Inhibit cysteine proteases especially in bacteria. Antimicrobial role (antibacterial and antiviral)
Alternative name for gustin
carbonic anhydrase VI
Function of gustin
facilitates taste by activating taste buds. (somehow to do with CO2 + H2O <-> H+ + HCO3-
Which ion is found in gustin / carbonic anhydrase VI?
Zn
Why might taste changes be a side effect of Viagra?
Gustin is the protein that facilitates taste and it is a potent PDE 5 activator which can be affected by Viagra (uses PDE 5 (phosphodiesterase 5) inhibitors).
What are histatins?
Histidine-rich proteins
Function of histatins
antibacterial (inhibits Streptococcus mutans) and antifungal (inhibits Candida albicans). Also inhibits CaPO4 precipitation which allows saturation of Ca and PO4 in saliva for remineralisation.
What are immunoglobins?
(Ig) - antibodies
Which cells secrete immunoglobins?
Plasma cells in salivary glands
Which immunoglobin is secreted in saliva?
IgA (short term memory) so would have to do yearly vaccinations against S. mutans
Why are there no vaccinations against S. mutans?
Because only IgA is secreted in saliva so would have to do yearly vaccinations. However, if someone is repeatedly vaccinated with the same antibody, the risk of anaphylactic shock increases.
Function of immunoglobins
Specific immunity against bacteria, fungi, viruses (Antibacterial, antifungal and antiviral)
Function of lactoferrin
Binds to Fe3+ so acts as an antibacterial especially against bacterial that require Fe (can grow on blood agar, relevant for gingival sulcus bleeding)
Where is lipase released from?
von Ebner glands (serous glands near circumvallate papillae) therefore called lingual lipase
Function of lipase
hydrolyses triglycerides (may assist in milk digestion)
Alternative name for mucoproteins
mucins
Structure of mucoprotein / mucin
CHO-protein macromolecule (lots of carbohydrate/CHO side chains) which can bind to tooth and epithelial surfaces
Function of mucin/ mucoprotein
binds to tooth and epithelial surfaces to lubricate and forms component of primary pellicle (part of biofilm). Promotes bacterial aggregation making clearance easier. Also helps bolus formation.
Function of proline-rich proteins (PRPs)
inhibit the growth of Ca3PO4 crystals, adsorbs onto hydroxyapatite, regulates bacterial attachment.
What is the advantage of proline-rich proteins inhibiting the growth of CaPO4 crystals?
Allows the supersaturation of Ca and PO4 in saliva which aids mineralisation
What is the advantage of proline-rich proteins adsorbing onto hydroxyapatite?
Acts as a diffusion barrier, decreases mineral loss, resists acid attacks, allows remineralisation
Function of statherins
prevent precipitation of Ca3PO4 from saliva so it is supersaturated with Ca and PO4, allowing remineralisation. Also has an anti-calculus effect.
Which plasma-derived substances ‘spill over’ into saliva?
Proteins (e.g. albumin), immunoglobins (IgG), hormones and drugs
Why can the presence of drugs / hormones be tested using saliva?
Drugs and hormones are plasma-derived substances that can enter saliva
Which salivary constituents have antimicrobial functions?
Immunoglobins, lactoferrin, lysozyme, mucins, histatins, cystatins, lactoperoxidase
Which salivary constituents have buffering functions?
Proteins (Histatins), phosphate, bicarbonate,
Which salivary constituents have digestive functions?
Gustin (Zn), amylase, lipase, (protease, DNAase, RNAase) mucin
Which salivary constituents have lubricative function?
mucoprotein/mucin
Which salivary constituents have remineralising function?
Prolin-rich proteins (PRPs), slatherin, histatins (inhibit CaPO4 precipitation), Ca, PO4
How can control of salivary secretion be divided?
Unconditioned (innate) and conditioned responses (learned through association)
What are the unconditioned salivary stimuli?
mechanical (pressure on PDL / oral mucosa) and chemical (gustation, olfaction, common chemical sense)
Which major salivary glands produces the most saliva during chewing/mechanical stimuli?
Parotid gland (50%)
Does pressure / chewing on one side of the mouth stimulate ipsilateral or contralateral gland secretion?
Ipsilateral - e.g. chewing on left side, stimulates secretion from left gland
Where are gustatory receptors on taste buds located?
Tongue dorsum, palate, epiglottis
Order of potency of saliva stimulation of different tastes
acid > umami = salt > sweet > bitter
Where are olfactory receptors located?
In the olfactory epithelium (very weak salivary stimulus)
What is common chemical sense?
An unconditioned chemical stimuli that contributes to taste of spices
Why is the common chemical sense a primitive response to irritants/injury?
It increases saliva for protection (e.g. in case of vomiting)
Which receptors mediate the common chemical sense?
Nociceptors in mucous membranes
Examples of conditioned salivary stimuli
psychic (thinking about food), visual, auditory (e.g. Pavlov)
What happens if conditioned stimuli are not regularly reinforced?
response is lost / becomes extinct
How do conditioned responses arise?
Start with an unconditioned stimulus UCS (e.g. food) which causes salivation and a conditioning stimulus CS (e.g. bell) which doesn’t cause salivation. UCS and CS are repeated together which causes salivation. When the CS occurs on its own it will cause salivation.
Which nerves control salivation?
Parasympathetic and sympathetic nerves
Effect of parasympathetic nerves on salivary secretion
increase secretion (ACh)
Effect of sympathetic nerves on salivary secretion
increase secretion
Effect of parasympathetic nerves on blood vessels near the salivary glands
vasodilation (blood directed to digestive system)
Effect of sympathetic nerves on blood vessels near the salivary glands
Vasoconstriction (reduce blood flow)
What are the 2 stages in the mechanism of salivary secretion?
Primary secretion in acinus and secondary modification in ducts
Overview of how primary secretion occurs in the acinus
ACh binds to receptor on acinar cell causing Ca2+ to be released in the cell which opens the Cl- channel. Cl- enters the cell via Cl-/K+ pump and diffuses through cell into intercalated duct. Na+ moves from blood to lumen via diffusion though acinar cell. Water follows NaCl by osmosis. CO2 from the blood diffuses into acinar cell. CO2 + H2O -> H+ + HCO3 - (carbonic anhydrase). HCO3- enters lumen of duct.
Which ions are reabsorbed / secreted in the secondary modification in the ducts?
Na+ and Cl- are reabsorbed into the acinar cells whereas K+ and HCO3- are secreted into the saliva.
How is Cl- and Na+ reabsorbed and K+ secreted in secondary modification?
Cl-/Na+ pump transports both ions into acinar cell. Cl- diffuses out into the blood via a Cl- channel and Na+ moves into the blood via a Na+/K+ pump which simultaneously moves K+ into the acinar cell. K+ enters saliva.
Comparison of final saliva to blood plasma
saliva is hypotonic to plasms (Na+ and Cl- ions removed from saliva)
