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IOE > Saliva - composition + secretion > Flashcards

Saliva - composition + secretion Flashcards

1
Q

list the 5 roles saliva is important in

A

1) lubrication
2) maintenance of oral hygiene
3) maintaining tooth mineralisation
4) digestion
5) solvation

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2
Q

important lubricant: which property makes saliva able to be a lubricant

A

mucous content

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3
Q

important lubricant: where is this important

A

speaking (speakers often have water because mouth can dry up)
eating

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4
Q

important lubricant: what does saliva do when eating

A
  • surrounds food
  • assists its passage down the oesophagus
  • if taste is bad = lots of saliva secreted to dilute it
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5
Q

important lubricant: what happens when we drink hot drinks

A
  • the hot solution mixes with saliva

- so it is diluted and cooled

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6
Q

maintenance of oral hygiene: which enzymes are contained in saliva and aids its antibacterial actions

A

lysozyme
- attacks bacterial cell walls
peptidases + peroxidases etc…
- destroy bacteria

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7
Q

maintenance of oral hygiene: what does saliva wash out

A

food particles between teeth

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8
Q

maintenance of oral hygiene: what is lactoferrin

A
  • found in saliva
  • an iron collator
  • removes iron
  • prevents bacteria growing as they require iron to do so
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9
Q

maintaining mineralisation: how does saliva achieve this

A
  • neutralises acid (corrosive to teeth) from vomiting or eating acidic food
  • inorganic compounds (ie Ca, F) are secreted into it and are incorporated into teeth to maintain mineralisation
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10
Q

maintenance of oral hygiene: what is xerostomia

A

dry mouth
can inc cavity risk
saliva can protect teeth by preventing its onset

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11
Q

digestion: which digestive enymes are contained in saliva

A

amylase (PTYALIN in saliva)

  • alpha amylase (1,4-glucan 4-glucanohydrolase) = main protein + digestive enzyme in saliva
  • carbohydrate break down

lipases (LINGUAL LIPASE in saliva)

  • only activated at pH 4 as food moves to stomach
  • fat break down
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12
Q

maintenance of oral hygiene: why isnt this function vital

A

digestion would still occur in stomach or small intestine if these enzymes weren’t present

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13
Q

solvation: what is role of saliva in solvation

A
  • dissolves and washes away food particles from tastebuds

- allows next mouthful of food to be tasted

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14
Q

what are the 3 major salivary glands, the % of saliva secreted they make up and what type of saliva they produce
give their locations

A
  • parotid (25%, serous) - near angle of jaw + ear
  • submandibular (70%, sero-mucin) - just below jaw
  • sublingual (5%, mucin) - beneath tongue
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15
Q

what type of secretion is saliva

A

exocrine (from a ductal system)

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16
Q

what is serous saliva

A
  • thin watery

- contains proteins from serous cells

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17
Q

what are mucins

A
  • family of glycoproteins
  • make up mucus (highly viscus fluid)
  • produced from mucus cells
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18
Q

what amount of saliva is produced daily

A

1500ml

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19
Q

what are acini

A

ball like clusters of epithelial cells in salivary glands

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20
Q

what do acini epithelial cells secrete

A

primary secretion

- mainly water, electrolytes, inorganic ions and enzymes

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21
Q

what happens to primary secretion

A

composition modified by secretion from epithelial cells lining the duct (they secrete or remove ions + h2o)

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22
Q

what is salivon

A

functional unit of a salivary duct

contains a blind end (ACINUS) comprised of acinar cells so secretes primary secretion

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23
Q

how is the rate of fluid secretion from the salivon influenced

A

myoepithelial cells surrounding acinar cells contain smooth muscle so contract + relax

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24
Q

where does fluid move to from the acinus

A

through intercalated ducts (area responsible for controlling rate of saliva secretion)

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25
Q

how is fluid flow influenced in intercalating duct

A
  • cells lining it contain smooth muscles
  • restrict fluid flow by constricting to dec size of lumen
  • increase fluid flow by dilating
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26
Q

what does the intercalated duct widen to become

A

the striated duct (lined by COLUMNAR epithelial cells)

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27
Q

what happens in the striated duct

A

the most modification to the primary secretion

28
Q

where does fluid flow after the striated duct

A

excretory duct

29
Q

what are the 3 main constituents of saliva

A

1) water
2) electrolytes
3) enzymes

30
Q

which ions / electrolytes does saliva contain in high and low levels relative to plasma

A 
high
- K+
- HCO3^-
low
- Na+
- Cl-
31
Q

what sort of process is saliva secretion, how

A

2 step

1) primary secretion
- from acini
- similar composition to plasma but also contains mucin + digestive enzymes
2) secondary secretion
- takes place in striated ducts
- modifies the composition

32
Q

what else takes place and modifies the composition

A

absorption

33
Q

what happens during secondary secretion

A
  • Na+ and Cl- reabsorbed from duct
  • K+ and HCO3^- secreted in but to lesser extent
  • SO saliva becomes HYPOtonic (previously isotonic)
34
Q

why does saliva become hypotonic

A
  • ductal epithelium has low permeability to water

- water NOT reabsorbed therefore becomes hypotonic

35
Q

explain the two-stage hypothesis

A

in the acinus

  • water, electrolytes, Na+, Cl-, HCO3^- enter
  • this is ISOTONIC primary secretion

as it moves into striated duct

  • lot of Na+, Cl- reabsorbed
  • more K+, HCO3^- secreted by cells lining the duct BUT not enough to balance ions leaving

so normally

  • H2O moves out of duct
  • but duct impermeable to H2O so get hypotonic solution
36
Q

what is hypotonic solution of saliva

A
  • dilute
  • lots of K+ and HCO3^-
  • less Na+ and Cl-
37
Q

how is sodium reabsorbed into the epithelial cells across the apical membrane (lines lumen of the duct)

A

via
the ENaC channel (epithelial sodium channel)
and
sodium-hydrogen exchanger

38
Q

once reabsorbed, how does sodium exit into the interstitial space across the basolateral membrane (lines interstitial space)

A

uses the Na-K pump

39
Q

how is Cl- reabsorbed into the epithelial cell across the apical membrane

A

via the apical

Cl- - HCO3^- exchanger

40
Q

how does Cl- exit epithelial cell across the basolateral membrane into the interstitial space

A

down apical chloride channels

41
Q

how is bicarbonate secreted from the epithelial cell, across the apical membrane into the lumen of the duct

A

via the Cl- - HCO3^- exchanger

42
Q

how does bicarbonate enter the epithelial cell

A

unsure

basolateral step not well understood

43
Q

how does potassium secretion occur via the salivary duct transporters of the epithelial cells

A

begins w basolateral uptake of K+ via Na-K pump

followed by exit of K via apical K-H exchanger

44
Q

-

A

-

45
Q

what does the final composition of saliva depend on

A

rate of secretion (as flow rate changes, ionic composition changes)

46
Q

what is the composition of saliva at high flow rate

A
  • similar electrolyte concs to plasma
  • composition similar to primary secretion
  • not enough time for secondary modification (reabsorption/secretion) to take place
  • except for bicarbonate
47
Q

why is concentration of bicarbonates higher than plasma at high flow rates and why is this a good thing

A
  • its transport is strongly influenced by stimulants of salivary secretion
  • important because it is alkaline SO when need high flow rates (ie when about to vomit / eaten acidic food - require large amount of saliva to neutralise acid + protect teeth), our saliva is alkaline due to large amounts of bicarbonate
48
Q

what is salivary composition at low flow rates

A
  • hypotonic solution
  • much less Na+ and Cl- as its resorbed
  • more K as its secreted
  • time for secondary modification (reabsorption/secretion) to occur
49
Q

what 4 experiments provide evidence for two-stage hypothesis

A

1) flow rate curves
2) acinar/intercalated duct micropuncture
3) transport properties of isolated, perfused ducts
4) polylysine injection

50
Q

how are flow rate curves created

A
  • measure salivary flow rate under different stimulants

- look at electrolyte concentrations within them

51
Q

how is duct micropuncture carried out

A

1) note composition independent of flow rate
2) do micropunture
3) look at flow rate

52
Q

what does poly-lysine injection do

A

1) poisons ducts
2) inhibits secondary reabsorption process
3) saliva becomes like primary fluid

53
Q

which system controls rate of salivary flow / secretion

A

autonomic nervous system (split into parasympathetic and sympathetic systems)

54
Q

what does stimulation of BOTH the parasympathetic AND sympathetic systems do

A

increase saliva secretion

55
Q

explain the role of the parasympathetic stimulation

A
  • largest role

- involved in production of copious flow of watery saliva and vasodilation

56
Q

how does parasympathetic stimulation increase salivary secretion

A

1) release acetylcholine (neurotransmitter)
2) acts on muscarinic receptors
3) causing contraction of myoepithelial cells surrounding the acinus
4) so acinus expels more saliva

57
Q

what else is released upon parasympathetic stimulation

A

vasoactiveintestinal peptide (VIP)

1) causes vasodilation
2) increasing blood flow and o2 delivery
3) allows increased secretion

58
Q

explain the role of the sympathetic stimulation

A
  • produces small amount of more mucus + enzyme rich saliva
59
Q

how does sympathetic stimulation increase salivary secretion

A

1) releases adrenaline and noradrenaline
2) these act on adrenoreceptors
3) causes myoepithelial cells to contract

60
Q

why is the autonomic nervous system activated / how does the body know we require saliva?

A

1) physical things
2) higher brain centres (involuntary effects)
3) prior to sickness, nausea, water brash

61
Q

which physical things activate the ANS reflex stimulation and secretion

A
  • food in mouth

- chewing

62
Q

how do higher brain centres stimulate ANS

give an example

A
  • conditioned reflex
  • stimulation comes from higher brain centres rather than food itself
  • ie Pavlov’s dogs with the bell
63
Q

how do sickness, nausea or water brash stimulate the ANS

A
  • reflux of acid coming up oesophagus stimulates excessive secretion of alkaline saliva
  • this neutralises stomach acid, protecting the teeth
64
Q

what is the name of the part of the brain responsible for sending signals out via to ANS to increase/decrease production

A

salivary centre

65
Q

how does the salivary centre work

A

1) detects various signals which it acts on
ie physical (smell / taste of food, food in mouth, chewing)
higher brain centres (fear, dehydration, excessive exercise, mental concentration= dec saliva production) or
conditioned events
2) whatever the input it sends a signal through the parasympathetic or sympathetic nervous system

IOE (22 decks)

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