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GI lectures - semester 3 > Week 2.1 - physiology of the mouth (workbook) > Flashcards

Week 2.1 - physiology of the mouth (workbook) Flashcards

1
Q

what is the mouth a way into?

A

the GI tract

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2
Q

what is the function of the mouth?

A

disrupts food stuffs and mix with saliva to form boluses to be swallowed

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3
Q

what is the oral mucosa and teeth vulnerable to?

A

physical and chemical damage, & infection

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4
Q

what is a major function of saliva in the oral environment?

A

ensuring a moist, chemically appropriate environment with a healthy bacterial flora

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5
Q

what is physical disruption of food by?

A

mastication (chewing)

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6
Q

what is mastication carried out by?

A

powerful muscles - mainly the masseter muscle

generate huge forces

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7
Q

what is the masseter muscle innervated by?

A

branch of trigeminal nerve

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8
Q

how is the force transmitted to food?

A

via teeth

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9
Q

what d the incisors and molars do?

A

incisors cut food into pieces

molars crush food and mix with saliva to form paste (to be swallowed)

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10
Q

what happens to the bolus?

A

moistened and lubricated by saliva

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11
Q

how much saliva do we produce each day from what?

A

1.5 litres of saliva from 3 pairs of salivary glands

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12
Q

what is the function of saliva?

A

moistens and lubricates food for swallowing and also contains enzymes which begin the digestion of (particularly) carbohydrates

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13
Q

what is a much more significant role of saliva?

A

protection of oral environment

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14
Q

mucosa and saliva

A

mucosa is not cornified and must be kept wet (by saliva)

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15
Q

what are teeth constantly at risk from?

A

from bacterial acid, which needs to be neutralised, and the bacterial ecology of the mouth needs to be maintained by mild bactericidal action

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16
Q

what is zerostomia?

A

no saliva secretion in the mouth

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17
Q

what happens in zerostomia?

A

we can eat without saliva, but if there is no secretion, the mouth very rapidly deteriorates

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18
Q

what type of solution is saliva?

A

a hypotonic solution

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19
Q

what is a hypotonic solution?

A

excess water over the other body fluids) with relatively low concentrations of Na+ & Cl-, but with excess concentrations of K+ and HCO3-

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20
Q

how is resting saliva like? what can happen to it?

A

resting saliva is neutral, once stimulated, it becomes alkaline

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21
Q

what does saliva contain aside from enzymes?

A

significant mucus

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22
Q

where is saliva secreted from?

A

3 pairs of salivary glands

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23
Q

what are the 3 pair of salivary glands?

A

parotid glands
sub lingual glands
sub maxillary glands

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24
Q

how much of the saliva is secreted by the parotid glands? and what type of saliva?

A

25% of saliva by volume

serous secretion with a mixture of water, electrolytes and enzymes

25
Q

how much of the saliva is secreted by the sub lingual glands (under tongue)? what type of saliva?

A

5% of saliva (don’t want too much mucous)

saliva is rich in mucus - known as mucous saliva

26
Q

how much of the saliva is secreted by the sub maxillary glands (behind & inferior tongue)? type of saliva?

A

about 70% saliva

secretes both serous and mucous components

27
Q

what are salivary glands composed of?

A

numerous blind ended tubes, with acini (secretory component of ducts) at blind end and ducts converging to outlets in the mouth

28
Q

are serous acini and mucus acini the same?

A

no, different in structure

29
Q

what type of acini does the sub maxillary gland contain?

A

mixture of both as it secretes both serous and mucus acini

30
Q

what is saliva made from and how does it compare?

A

made from plasma, but always hyPOtonic to plasma

31
Q

how is hypotonicity of saliva achieved?

A

NOT by directly pumping water
by first secreting an isotonic solution (same ionic component as plasma), then removing ions from it (less ions than plasma)

32
Q

what do acinar cells secrete?

A

an isotonic fluid containing enzymes

33
Q

what do duct cells do?

A

remove Na+ & Cl- (salt) and add HCO3-

34
Q

how are the gap between ducts cells like? why?

A

tight, so water doesn’t follow the resulting osmotic gradient, and saliva remains hyPOtonic

35
Q

what happens at low flow rates of saliva out of acinar cells?

A

duct cells remove most of the Na+, so saliva is VERY hypotonic

36
Q

what is the capacity of the duct cells to modify saliva? what does this mean?

A

very limited, so at high flow rates, a smaller fraction is removed, and saliva becomes less hypotonic (still lots of NaCl and not enough HCO3-, more isotonic)

37
Q

what happens to the stimulus to secrete by duct cells at high flow rates?

A

promote HCO3- secretion, so saliva becomes more alkaline, although not enough NaCl removed (not hypotonic)

38
Q

what does high flow rate (stimulated) result in, in terms of volume, hypotonicity, alkalinity & enzyme content)?

A

high volume, low hypotonicity, high alkalinity (duct cells secrete HCO3-), high enzyme content (more saliva = more enzymes)

39
Q

what is salivary secretion mostly controlled by?

A

the ANS (involuntary)

40
Q

what stimulates the acinar cells? to produce what?

A

parasympathetic nerves (rest & digest) from the otic ganglion stimulate acinar cells to produce primary secretion (of isotonic saliva)

41
Q

what stimulates the duct cells? to do what?

A

also parasympathetic nerves from the otic ganglion (same as acinar cells) to add extra HCO3- to saliva

42
Q

what does salivary volume depend on?

A

ANS control - controlling amount secreted from acinar cells

43
Q

how is ANS outflow coordinated?

A

from the brain stem in response to afferent stimuli (entering brain stem)

44
Q

what are afferent stimuli that can affect antonomic outflow?

A

smell & taste of food & conditioned reflexes (e.g. pavlov’s dog)

45
Q

what does sympathetic nervous activity do to salivary glands?

A

reduces blood flow to the salivary glands (vasoconstrict), which limits salivary flow, producing the typical dry mouth of anxiety - need blood for outflow of saliva

46
Q

what is the rate of ductal recovery of Na+ increased by (taking Na+ away - produce hypotonic saliva)?

A

hormone aldosterone from adrenal cortex (zona glumerulosa - outermost layer)

47
Q

what happens once saliva is mixed with chewed food?

A

forms bolus, it must be swallowed

48
Q

how is swallowing carried out?

A

in 3 phases:

  1. voluntary phase
  2. pharyngeal phase
  3. oesophageal phase
49
Q

what is the main purpose of the voluntary phase?

A

a bolus is moved onto the pharynx

50
Q

what happens in the pharyngeal phase?

A

afferent information from receptors in the pharynx reaches the swallowing centre in the brain stem

51
Q

what happens when afferent information from pharynx receptors reaches swallowing centre in brain stem? (pharyngeal phase)

A

triggers a set of movements, including:

  1. inhibition of breathing - prevent aspiration
  2. raising of larynx (to meet epiglottis)
  3. closure of glottis (airways) - by epiglottis
  4. opening of entrance to oesophagus (to travel to stomach)
52
Q

what type of muscle is in the upper 1/3 of the oesophagus?

A

voluntary straited

53
Q

what type of control is the muscle of the upper 1/3 of the oesophagus under?

A

somatic nerves (voluntary) - as opposed to automonic, so upper 1/3 is an active movement we choose to carry out

54
Q

what type of muscle is in the lower 2/3 of the oesophagus?

A

smooth muscle

55
Q

what type of control is the muscle of the lower 2/3 of the oesophagus under?

A

parasympathetic nervous system (part of ANS, involuntary), rest & digest

56
Q

what happens in the oesophageal phase?

A

a wave of peristalsis sweeps down the oesophagus, propelling the bolus to the stomach in about 9 seconds

57
Q

what are the oropharynx and the oesophagus essentially?

A

highways concerned with passing ingested food to the stomach and intestines for digestion (& absorption)

58
Q

what are the oropharynx and the oesophagus open to?

A

potentially hazardous environment & are potentially under threat of attack from a number of directions

GI lectures - semester 3 (6 decks)

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