Salivary Physiology Flashcards
What are the characteristics of Saliva?
- Saliva is Hypotonic fluid (relative to plasma)
- 99% water and less than 1% dry matter (e.g. proteins and salts)
- Daily Normal Production = 0.5-1.5 litres
- In resting state = 2/3 of the volume produced by Submanibular glands
- Stimulated state = 60% of volume produced by PAROTID GLANDS
What’s the composition of Saliva?
- > 99% Water
Contains:
- Electrolytes/inorganic constituents
- Organic constituents
- Hyptonic
What Electrolytes are present in Saliva?
Cations: \+ Sodium \+ Potassium \+ Calcium \+ Magnesium
Anions:
- Bicarbonate
- Chlorine
- Phosphates
- Fluorine
What’s the 2 stage hypothesis for the production of a hypotonic saliva?
Stage I:
- Electrolyte transport by the acinar cell to produce Isotonic saliva (PRIMARY SALIVA)
Stage II:
- Ductal modification of electrolyte composition of the primary saliva to produce HYPOTONIC SALIVA
Stage I: What are the steps?
I: Increase in acini permeability to Calcium
- Acetylcholine creates action potential
- Increase in Calcium influx into the cell
- Causes release of Potassium in the Interstitium
- Chloride and Bicarbonate release into the lumen
- Negative charge in the lumen
- Influx of Sodium into the lumen
II: Influx of Sodium
- Via a concentration gradient
- Now have a salty fluid
III: Transepithelial water influx
- Water move into the Lumen via Aquaporins in the cells
- Movement is passive whilst ion movement is active-transport
- Movement causes cells to shrivel
IV: Acinar cell shrinkage and increased intracellular Sodium conc
- Calcium (-) conc increase also opens Sodium-Hydrogen channels
- Influx of Sodium
V: Re-establishing the original prestimulatory ion gradient
Stage II: What are the steps?
I: Extrusion of Sodium from the duct cell to interstitium
- Energy is required
- Activation of Na/K pump = cells lose Sodium to the Interstitium & Gain Potassium
II: Reabsorption of Sodium and Chlorine
- Sodium and Chlorine are reabsorbed into the cells from the Lumen/Saliva
- Increase in H+ and Bicarbonate in the saliva
How does the flow rate alter the composition of saliva?
High Flow Rate:
- High in Bicarbonate/Chlorine/Sodium
- Cannot be reabsorbed
- Low in Potassium
- Cannot be added
Formation of Organic constituents of Saliva?
- Mostly secreted by acinar cells (ductal cells to lesser extend)
- Protein conc. depends on both the duration of stimulus and on the flow rate
(Long period of stim. = in high saliva total protein conc)
What are the secretory pathways?
- Constitutive exocytosis - occurs continuously (more predominant in minor glands)
- Regulated exocytosis (mainly major glands)
What’s exocytosis?
- Process by which a cell transports secretory products through the cytoplasm to the plasma membrane
- They are then released
(stimulated by Calcium concentrations - channel opens + influx causes exocytosis)
What’s Constitutive exocytosis?
- Proteins NOT concentrated into secretory vesicles awaiting exocytotic stimulus
- There’s a continuous flow of proteins in small vesicles to the plasma membrane (no ongoing external stimuli
What’s Regulated Exocytosis?
- Acceleration of Constitutive exocytosis
- Controlled by dual (para)sympathetic secretomotor innervation
- After synthesis the proteins are stored in granules — stimulation causes the granules to empty their content into the lumens
How does Saliva have a buffering action?
- Acid from plaque/food+drink causes enamel wear
- Host fats act as a buffer (only resting secretion)
- Bicarbonate = MAIN BUFFER
- Mainly from Major Glands
- Concentration increases with flow rate
- Minimises the drop in pH around teeth after consumption of sugar/acids
What’s the Buffering Capacity?
- Ability of the saliva to maintain the pH when exposed to acids
What does the Stepthan Curve show?
- Effect pH has on remineralisation & demineralisation
- Critical pH 5.5
- > 5.5 = REMINERALISATION
- <5.5 = DEMINERALISATION
How does Saliva remineralise the teeth?
- Typically it is supersaturated with Calcium and phosphate
- Fluoride also present
What are some of the organic components to Saliva?
Protein:
- Enzymes
- Serum Albumin
- Immunoglobulins
- Lactoferrin
Carbohydrates
Lipids
Organic Components of Saliva: What’s Salivary Amylase?
- Secreted by Parotid glands
- 1st stage of carbohydrate digestion
- Breaks down Polysaccharides to Dissaccharides
- Inactivated by acid in the stomach
- Breaks down starch in plaque?
Organic Components of Saliva: What’s Salivary Lipase?
- From Lingual minor glands (Serous Glands of Von Ebner)
- 1st stage of fat digestion
+ significant role - Remains active at gastric pH unlike Amylase
+Important in digestion of milk fat in newborn
Organic Components of Saliva: What’s Mucin (Mucous Glycoproteins)?
- Complex molecules
+ Peptide core
+ Oligosaccharide chains - Mucin + water = mucus
- Lubricant
- Coats all oral soft tissues (prevents drying acts as a barrier)
Organic Components of Saliva: What’s Statherin?
- Prevents precipitation of Calcium and Phosphate = supersaturation
- Good for mineralisation of teeth
- Present in Enamel Pellicle
- Some Antimicrobial properties
Organic Components of Saliva: Secretory IgA?
- Mainly from minor glands
Composed of:
- IgA
- Secretory piece
- IgA is synthesised by plasma cells in CT around the glands + modified/secreted by acinar and duct cells
- Directed against specific antigens
- Provides local immunity
What Antimicrobial components are present in Saliva?
Amylase:
- Interferes with bacterial adherence
Lysozyme:
- Cleaves polysaccharide component of bacterial cell wall
Histatins:
- Inhibits growth of Candida Albicans
Lactoferrrin:
- Binds Iron - inhibiting bacterial growth and adhesion of bacteria to epithelial surfaces
Neural Control of Salivary Secretions: What’s the effect of the Parasympathetic nervous system?
- Parasympathetic nerves stimulation evoke a copious flow of saliva
Parotid:
- Brainstem Salivary Nuclei
- Parasympathetic Nerves (IX) to the Otic Ganglion
- Auriculotemporal Nerve
- Parotid gland
Submandibular & Sublingual:
- Brainstem Salivary Nuclei
- Parasympathetic Nerves (VII) to the Submandibular ganglion
- Glands
- Aceylcholine release
Neural Control of Salivary Secretions: What’s the effect of the Sympathetic nervous system?
- Causes saliva secretions
All Glands:
- Thoracic Spinal Cord (T1-T4)
- Sympathetic nerve fibres to the Superior Cervical Ganglion
- Sympathetic nerves to all glands
Reflex control of Salivary Secretions: What’s a reflex?
- Innate, automatic, predictable, goal-directed response involving the CNS to a known stimulus
- Usually associated with feeding
What’s Unconditioned Reflex?
- Mechanoreceptors and chemoreceptors in the mouth sigal the Salivary centre in the Medulla
- Causes Automonic Nerves stimulation
- Salivary gland stimulation
- Increase in salivary secretions
What’s Conditional Reflex?
- Other inputs are directed to the Cerbral cortex which stimulates the Salivary centre in the medulla (input from higher centres in the brain)
- Causes Autonomic nerve stimulation
- Stimulation the salivary glands
- Increases salivary secretions
What’s Gustatory-Salivary Reflex?
- Stimuli delivered to gustatory receptors in taste buds
- Basic taste causes salivary secretions
- Facial nerve (VII) in anterior 2/3 signals to the medulla oblongata
- Goes to Thalamus
- Goes to Gustatory cortex
- Sour taste has the greatest effect on secretions
What’s the Masticatory-Salivary reflex?
- Mechanoreceptive efferent neurons innervate the: \+ Periodontal ligament \+ Oral mucosa \+ TMJ \+ Muscle
- Trigeminal nerve (V)
- Reflex pathway is unilateral - stimulation of one side of the mouth induces out IPSILATERAL SALIVATION
(Chew on one side causes saliva secretion on that side)
Conditioned Salivary Reflex: How does it occur?
- Dog salivates in response to food
- Dog doesn’t salivate in response to tuning fork
Conditioning:
- Tuning fork + food causes salvation
- Repeat x no. of time
- Tuning fork and no food causes salivation
= Dog is conditioned to link the sound with food which in turn causes salivation (higher centres are involved)
What factors affect salivary flow rate?
- Smell of food increases
- State of hydration (dehydrated decreases)
-Ages decreases - Light:
+ Bright increases
+Dark decreases
What’s Xerostomia?
- Dry mouth
- Percieved when unstimulated flow is <50% normal
Cause:
+ Disease/damage
- Systemic (Sjogren syndrome)
- Intrinsic
- Extrinsic
+ Medications:
- Antidepressants
- Anti-histamines
+ Dehydration
+ Tobacco & Alcohol use
+ Stress & Anxiety
What are the physical impacts of dry mouth?
Oral Cavity:
- Food debris present on teeth or soft tissue
- Halitosis (bad breath)
Tongue:
- Dry and fissured tongue
- Atrophy of filiform papillae
Teeth:
- Dental caries
- Enamel demineralisation
Lips:
- Dry and cracked lips
What’s Sjogren’s syndrome?
- Long-term autoimmune disease that affects the body’s moisture-producing glands
Primary Symptoms:
- Dry eye
- Dry mouth (difficulty swallowing and speaking)
What’s the cause of Sjogren’s Syndrome?
- Unknown
- May be the influence of a combination of factors: Genetic/Hormonal/Environmental
How is Sjogren’s Syndrome diagnosed?
- Blood test to look for antibodies common in SS (Antinuclear Antibody ANA & Rheumatoid factor)
- Salivary flow test
- Lip/salivary gland biopsy - tissue sample taken; revealing lymphocytes clustering around salivary glands
