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BS - Gastrointestinal System pt.1 > Mouth & Swallowing > Flashcards

Mouth & Swallowing Flashcards

1
Q

What functions of the GI tract are applicable to the mouth?

A
  1. ingestion
  2. mechanical processing
  3. digestion
  4. secretion
  5. limited amounts of absorption and excretion
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2
Q

What substances are absorbed in the mouth?

A

The mucosa under the tongue is highly vascularised so some substances are absorbed here

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3
Q

Why may drugs be given ‘sub-lingually’?

A

The blood supply goes straight to the heart and does not travel to the liver

This prevents the drug being broken down in the liver allowing it to work more rapidly and have a greater effect

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4
Q

When is excretion performed via the mouth?

What may induce this?

A

Toxins and irritants in the stomach induce vomiting

An obstruction in the small bowel can also cause vomiting

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5
Q

What is meant by the hard palate providing an ‘anvil’?

A

The muscular tongue squashes food against the hard palate, forming it into boluses for swallowing

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6
Q

What is the role of the soft palate?

A

Along with the epiglottis, the soft palate ensures that food and air don’t end up in the wrong places

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7
Q

What is the role of the lips?

A

They act as a guard

They are opened to allow food to enter the mouth, but closed to prevent it exiting while it is being processed

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8
Q

What is the role of the teeth?

A

The rig of teeth is present for mechanical processing

There are different teeth which are suited to processing different types of food

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9
Q

where are the incisors found and what is their role?

A

They are present at the front of the mouth

They act like blades, designed to cut off a piece of food

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10
Q

Where are the cuspids (canines) and what is their role?

A

They are the pointed teeth behind the incisors

They spike into foods allowing them to be teared

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11
Q

why do the cuspids have their name?

A

they have a single root

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12
Q

Where are the premolars (bicuspids) and molars found?

How many roots do they have?

A

The premolars are behind the cuspids (canines) and have 2 roots

The molars are behind the premolars and have 3 - 4 roots

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13
Q

What are the roles of the premolars and molars?

A

They crush and grind food, especially as the jaw moves laterally as this grinds food between the upper and lower teeth

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14
Q

What are the 3 functions of the muscles of mastication (chewing)?

A
  1. closing the jaw
  2. sliding or rocking of the lower jaw from side to side
  3. chewing

The tongue and cheeks help to move food across the teeth

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15
Q

what are the 3 types of movement involved in chewing?

A

It involves mandibular:

  1. elevation and depression
  2. protraction and retraction

3, medial and lateral movement

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16
Q

What is the main role of saliva?

Why is this important?

A

It has a role in lubrication of both the mouth and the food

This allows things to move more easily and it helps to keep the mouth clean

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17
Q

What types of fluid are found within saliva?

A

Serous fluid which contains enzymes

Mucous which makes it ‘slippery’

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18
Q

How does saliva help in protection against acid and bacteria?

A

It contains antibacterial enzymes, such as lysozyme and IgA

It contains bicarbonate and calcium ions, which prevent the mouth from becoming too acidic

Calcium helps to stop the teeth from dissolving in acid

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19
Q

How does saliva have a role in digestion?

A

It contains enzymes:

  1. salivary amylase (ptyalin) breaks down carbohydrates
  2. lingual lipase begins to break down fats
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20
Q

How is saliva production regulated?

A

Almost entirely by neural control

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21
Q

How does sympathetic and parasympathetic activity modulate saliva production?

A

They BOTH increase saliva production

Parasympathetic activity produces more serous fluid which carries enzymes (fluid-like)

Sympathetic activity increases mucous secretion (thicker)

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22
Q

What is the difference in the reasons for the sympathetic and parasympathetic stimulation of saliva production?

A

Sympathetic stimulation of saliva is to facilitate respiration

Parasympathetic stimulation is to facilitate digestion

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23
Q

What is the parasympathetic system that controls saliva production controlled by?

A

The salivatory centre in the brainstem

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24
Q

What signals in the salivatory centre in the brainstem will increase saliva production?

A
  1. local stimuli, such as taste and touch in the mouth

the sensory input in the mouth triggers saliva secretion

  1. central stimuli, such as smell and sight of food

this is the cephalic phase that involves taking signals from other senses

  1. learned reflex, such as Pavlov’s dog or time of day
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25
Q

What is the first stage in parasympathetic stimulation of saliva production?

A

Parasympathetic stimulation leads to acetylcholine release onto the salivary acinar cells

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26
Q

what is the role of acetylcholine in saliva production?

A

ACh binds to muscarinic receptors

This leads to an increase in intracellular calcium concentration

This is achieved through the IP3/DAG second messenger system

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27
Q

How does raised intracellular calcium concentration contribute to salivation?

A

Increased intracellular Ca2+ causes vesicles to fuse with the apical membrane

This leads to secretion

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28
Q

How does sympathetic stimulation lead to saliva secretion?

A
  1. sympathetic stimulation leads to the release of noradrenaline
  2. noradrenaline binds to adrenergic receptors
  3. this leads to an increase in intracellular calcium levels
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29
Q

What is an acinus?

A

A balloon of epithelial cells which produces a primary secretion

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30
Q

What is the primary secretion that is produced by the acini?

A

It is an initial isotonic (neutral) fluid

It mainly contains NaCl, protein and/or mucous

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31
Q

How is the isotonic primary secretion made?

A
  1. Cl- is moved into acinar cells and exported across the apical face of the cell
  2. bicarbonate moves in the same direction
  3. this leads to movement of Na+
  4. this leads to a primary secretion that is mainly isotonic saline
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32
Q

Why are proteins part of the primary secretion?

A

Proteins are excreted by exocytosis due to a calcium stimulus

33
Q

How is the secondary secretion formed?

A

As the primary secretion moves through the ducts, it is processed to form the secondary secretion

  1. Na+ is exchanged for protons
  2. Cl- is exchanged for bicarbonate

There is more bicarbonate than proton secretion

34
Q

How does the secondary secretion vary from the primary secretion?

A

It becomes increasingly alkaline and more hypotonic (dilute)

35
Q

Why is the flow rate through the ducts important?

A

If the flow rate is too high, there is not enough time for the primary secretion to be processed to the secondary secretion

This leads to the saliva in the mouth being more neutral

36
Q

what are the 3 salivary glands?

A
  1. parotid gland
  2. submandibular gland
  3. sublingual gland
37
Q

What is the role of the parotid gland?

A

it is the largest salivary gland

  1. it predominantly produces serous secretions (25% salivary volume)
  2. it is the main source of salivary amylase and proline-rich proteins
38
Q

What are proline-rich proteins?

A

they seem to collate molecules and play a role in protecting the teeth from damage

39
Q

what is the nervous supply to the parotid gland?

A

It receives parasympathetic supply via the glossopharyngeal nerve (CN IX)

It receives sympathetic supply via the superior cervical ganglion

40
Q

What is the role of the submandibular gland?

A
  1. produces a mixture of serous and mucous secretion (70% salivary volume)
  2. main source of lysozyme and lactoperoxidase
41
Q

What are the roles of lysozyme and lactoperoxidase in the mouth?

A

They are antibacterial so protect against bacterial infection

They prevent the teeth from decaying

42
Q

What is the nervous supply to the submandibular gland?

A

Parasympathetic supply from facial nerve (CN VII)

Sympathetic supply from superior cervical ganglion

43
Q

what is the role of the sublingual gland?

A
  1. predominantly produces a mucous secretion (5% salivary volume)
  2. main source of lingual lipase
44
Q

What is the nerve supply to the sublingual gland?

A
  1. Parasympathetic supply from facial nerve (CN VII)

2. Sympathetic supply from superior cervical ganglion

45
Q

What is the role of Ptyalin a-amylase?

A

It is involved in the initial digestion of polysaccharides

46
Q

What type of linkages are starch and other large polysaccharides made up of?

A

a-1,4 and a-1,6 linkages

a-1,6 linkages cause branches

47
Q

What are the molecules produced by ptyalin a-amylase and why?

A

a-amylases can only cut at a-1,4 sites and not adjacent to the a-1,6 sites

this leads to di- and trisaccharides and limit dextrins

48
Q

What is the optimum pH of ptyalin and when is it denatured?

A

Optimum pH is around 7

It is denatured at pH 4 so it denatured immediately as it comes in contact with stomach acid

49
Q

What is the role of lingual lipase?

A

It is involved in the initial digestion of triglycerides

It will cleave one fatty acid from the molecule

This leaves diacylglycerol and a free fatty acid

50
Q

what is the optimum pH of lingual lipase and when is it denatured?

A

Optimum pH is around 4, so it is stable in the stomach and works together with gastric lipase

It is denatured by pancreatic proteases

51
Q

How come lingual lipase is not very effective in the mouth?

A

The fat lumps need to be broken down into smaller units

Fats are not water-soluble so lingual lipase can only work on the outer edges of the molecules

52
Q

what are the 3 types of papillae that contain taste buds?

A
  1. foliate
  2. circumvallate
  3. fungiform
53
Q

What actually is contained within a papilla?

A

The clusters of cells embedded in them are taste buds themselves

They are specialised epithelial cells which have microvilli that sense the food in the mouth

54
Q

What do the epithelial cells within a tastebud release?

A

Neurotransmitters which will communicate with nerve cells

55
Q

what are the 2 types of taste bud?

A
  1. ion channel-based sensor

2. G protein-coupled receptor-based sensor

56
Q

What will an ion channel-based sensor detect?

What type of stimulus is this?

A

It detects a salty or sour stimulus

It detects protons

The sour stimulus comes from the presence of acid

57
Q

What does a salty stimulus lead to?

A

The opening of a sodium ion channel in the membrane

This leads to a sodium influx and depolarization of the membrane

58
Q

What does a sour stimulus lead to?

A

Protons bind to sodium channels in the membrane

The sodium influx depolarises the membrane and leads to the opening of Ca2+ ion channels

Calcium influx triggers the release of neurotransmitters

59
Q

What will a G protein-coupled receptor-based sensor detect?

A

Sweet, umami (savoury/glutamates) and bitter stimuli

60
Q

How does a G protein-coupled receptor-based sensor work?

A

All 3 stimuli signal through the calcium cascade and calcium-induced calcium release

This causes membrane depolarisation and the release of neurotransmitters

61
Q

What is the difference between odour receptors and taste sensors?

How are they linked?

A

Taste sensors are specialised epithelial cells

Odour receptors are nerve cells

Smell helps to fine-tune the response to the taste receptors

62
Q

How do olfactory (odour receptors) cells work?

A

The receptor cilia of the olfactory cells have GPCRs

These signal through cAMP to cause depolarisaiton that will trigger the action potential

63
Q

How does the food pass into the oesophagus?

A

Food passes from the oral cavity, through the oropharynx and laryngopharynx and to the oesophagus

64
Q

How are the soft palate and the epiglottis involved in preventing food and air from going to the wrong places?

A

The soft palate seals off the nasopharynx

The epiglottis seals off the bottom part of the oropharynx and the trachea

65
Q

How is the reflex involved in swallowing triggered?

A

The food bolus pushes against the soft palate

This initiates a reflex that causes the soft palate to rise and close off the nasopharynx

66
Q

What happens to the epiglottis and the upper oesophageal sphincter as a result of the swallowing reflex?

A

The epiglottis moves downwards to seal the trachea

The UES relaxes to allow the bolus to enter the oesophagus
Immediately after, it contracts to open the airway

67
Q

How is the food bolus carried to the stomach?

A

By peristalsis

68
Q

What are the dimensions of the oesophagus?

How is it innervated and how does it reside in the absence of food?

A

It is 25 cm long and 2 cm wide

It is flattened/collapsed in the absence of food

It is innervated by fibres from the oesophageal plexus

69
Q

What is the epithelium like in the oesophagus?

A

It has stratified squamous epithelium that is thrown into folds

Multi-layered epithelium means that, if a few cells are scraped off, they can easily be replaced

70
Q

What is the role of the submucosal oesophageal glands?

A

They secrete mucus to facilitate the passage of the food bolus

71
Q

what controls the behaviour of the epithelium in the oesophagus?

A

the lamina propria and the muscularis mucosae

72
Q

What is meant by tension waves in swallowing?

A

During swallowing, a wave of tension spreads down the oesophagus

73
Q

How is the tension wave created?

A
  1. the upper oesophageal sphincter is controlled by the swallowing reflex
  2. the reflex causes brief closure of the pharynx and opening of the UES
  3. a wave of tension forms behind the bolus which helps to push it down the oesophagus
74
Q

What happens to the lower oesophageal sphincter on swallowing?

A

It opens upon swallowing

75
Q

What is meant by the UES and LES having a degree of passive tone?

A

They sit closed by default

There is a specific action to open them when needed

76
Q

What is meant by the cephalic phase of GI activity?

A

Some control of GI activity is initiated before food is eaten, as it is anticipated

This involves a combination of stimuli

77
Q

What is the cephalic phase mediated by?

A

The parasympathetic nervous system

The vagus nerve carries signals both to and from the gut and can modify the cephalic phase

78
Q

What actions are produced during the cephalic phase and what are they controlled by?

A
  1. salivary secretion via the facial and glossopharyngeal nerve (CV VII and IX)
  2. control of GI motility and secretion via the vagus nerve (CN X)

BS - Gastrointestinal System pt.1 (22 decks)

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