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Oral Biology > Salivary Physiology > Flashcards

Salivary Physiology Flashcards

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1
Q

What are the characteristics of Saliva?

A
  • 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
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2
Q

What’s the composition of Saliva?

A
  • > 99% Water

Contains:

  • Electrolytes/inorganic constituents
  • Organic constituents
  • Hyptonic
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3
Q

What Electrolytes are present in Saliva?

A 
Cations:
\+ Sodium
\+ Potassium
\+ Calcium
\+ Magnesium

Anions:

  • Bicarbonate
  • Chlorine
  • Phosphates
  • Fluorine
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4
Q

What’s the 2 stage hypothesis for the production of a hypotonic saliva?

A

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

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5
Q

Stage I: What are the steps?

A

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

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6
Q

Stage II: What are the steps?

A

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
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7
Q

How does the flow rate alter the composition of saliva?

A

High Flow Rate:

  • High in Bicarbonate/Chlorine/Sodium
  • Cannot be reabsorbed
  • Low in Potassium
  • Cannot be added
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8
Q

Formation of Organic constituents of Saliva?

A
  • 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)
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9
Q

What are the secretory pathways?

A
  1. Constitutive exocytosis - occurs continuously (more predominant in minor glands)
  2. Regulated exocytosis (mainly major glands)
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10
Q

What’s exocytosis?

A
  • 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)

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11
Q

What’s Constitutive exocytosis?

A
  • 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
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12
Q

What’s Regulated Exocytosis?

A
  • 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
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13
Q

How does Saliva have a buffering action?

A
  • 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
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14
Q

What’s the Buffering Capacity?

A
  • Ability of the saliva to maintain the pH when exposed to acids
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15
Q

What does the Stepthan Curve show?

A
  • Effect pH has on remineralisation & demineralisation
  • Critical pH 5.5
  • > 5.5 = REMINERALISATION
  • <5.5 = DEMINERALISATION
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16
Q

How does Saliva remineralise the teeth?

A
  • Typically it is supersaturated with Calcium and phosphate

- Fluoride also present

17
Q

What are some of the organic components to Saliva?

A

Protein:

  • Enzymes
  • Serum Albumin
  • Immunoglobulins
  • Lactoferrin

Carbohydrates
Lipids

18
Q

Organic Components of Saliva: What’s Salivary Amylase?

A
  • 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?
19
Q

Organic Components of Saliva: What’s Salivary Lipase?

A
  • 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
20
Q

Organic Components of Saliva: What’s Mucin (Mucous Glycoproteins)?

A
  • Complex molecules
    + Peptide core
    + Oligosaccharide chains
  • Mucin + water = mucus
  • Lubricant
  • Coats all oral soft tissues (prevents drying acts as a barrier)
21
Q

Organic Components of Saliva: What’s Statherin?

A
  • Prevents precipitation of Calcium and Phosphate = supersaturation
  • Good for mineralisation of teeth
  • Present in Enamel Pellicle
  • Some Antimicrobial properties
22
Q

Organic Components of Saliva: Secretory IgA?

A
  • 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
23
Q

What Antimicrobial components are present in Saliva?

A

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

24
Q

Neural Control of Salivary Secretions: What’s the effect of the Parasympathetic nervous system?

A
  • Parasympathetic nerves stimulation evoke a copious flow of saliva

Parotid:

  1. Brainstem Salivary Nuclei
  2. Parasympathetic Nerves (IX) to the Otic Ganglion
  3. Auriculotemporal Nerve
  4. Parotid gland

Submandibular & Sublingual:

  1. Brainstem Salivary Nuclei
  2. Parasympathetic Nerves (VII) to the Submandibular ganglion
  3. Glands
  • Aceylcholine release
25
Q

Neural Control of Salivary Secretions: What’s the effect of the Sympathetic nervous system?

A
  • Causes saliva secretions

All Glands:

  1. Thoracic Spinal Cord (T1-T4)
  2. Sympathetic nerve fibres to the Superior Cervical Ganglion
  3. Sympathetic nerves to all glands
26
Q

Reflex control of Salivary Secretions: What’s a reflex?

A
  • Innate, automatic, predictable, goal-directed response involving the CNS to a known stimulus
  • Usually associated with feeding
27
Q

What’s Unconditioned Reflex?

A
  1. Mechanoreceptors and chemoreceptors in the mouth sigal the Salivary centre in the Medulla
  2. Causes Automonic Nerves stimulation
  3. Salivary gland stimulation
  4. Increase in salivary secretions
28
Q

What’s Conditional Reflex?

A
  1. Other inputs are directed to the Cerbral cortex which stimulates the Salivary centre in the medulla (input from higher centres in the brain)
  2. Causes Autonomic nerve stimulation
  3. Stimulation the salivary glands
  4. Increases salivary secretions
29
Q

What’s Gustatory-Salivary Reflex?

A
  • 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
30
Q

What’s the Masticatory-Salivary reflex?

A 
- 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)

31
Q

Conditioned Salivary Reflex: How does it occur?

A
  • 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)

32
Q

What factors affect salivary flow rate?

A
  • Smell of food increases
  • State of hydration (dehydrated decreases)
    -Ages decreases
  • Light:
    + Bright increases
    +Dark decreases
33
Q

What’s Xerostomia?

A
  • 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

34
Q

What are the physical impacts of dry mouth?

A

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

35
Q

What’s Sjogren’s syndrome?

A
  • Long-term autoimmune disease that affects the body’s moisture-producing glands

Primary Symptoms:

  • Dry eye
  • Dry mouth (difficulty swallowing and speaking)
36
Q

What’s the cause of Sjogren’s Syndrome?

A
  • Unknown

- May be the influence of a combination of factors: Genetic/Hormonal/Environmental

37
Q

How is Sjogren’s Syndrome diagnosed?

A
  • 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

Oral Biology (33 decks)

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