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ESA 3 - Gastrointestinal System > Salivation and Swallowing > Flashcards

Salivation and Swallowing Flashcards

1
Q

What is the entrace to the GI tract?

A

The mouth

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2
Q

What does the mouth serve to do?

A
  • Disrupts foodstuffs
  • Mix foodstuffs with saliva to form boluses
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3
Q

What can happen once food boluses have been formed?

A

They can be swallowed

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4
Q

What is the function of teeth?

A
  • Cut
  • Crush
  • Mix food with saliva
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5
Q

Which type of teeth cut?

A

Incisors

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6
Q

Which type of teeth crush?

A

Molars

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7
Q

What generates the force behind the teeth?

A

The powerul muscles of mastication, the Masseter

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8
Q

What innervates the Masseter?

A

A branch of the trigeminal nerve

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9
Q

What is the tongue?

A

A collection of 8 muscles

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10
Q

What does the tongue do?

A
  • Works to manipulate food for mastication and form it into a bolus
  • Aids swallowing by pushing bolus to back of mouth
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11
Q

Label this diagram

A
  • A - Nasopharynx
  • B - Oropharynx
  • C - Hypopharynx
  • D - Esophagus
  • E - Sinus
  • F - Nasal cavity
  • G - Salivary glands
  • H - Oral cavity
  • I - Trachea
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12
Q

Where does the oropharynx lie?

A

Behind the oral cavity

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13
Q

What does the oropharynx form?

A

The portion of the pharynx below the nasopharynx but above the laryngopharynx

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14
Q

Where does the oropharynx extend?

A

From the uvula (the end of the palate), to the level of the hyoid bone

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15
Q

What closes over the glottis?

A

A flap of tissue called the epiglottis

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16
Q

Why is the epiglottis needed?

A

To prevent aspiration, as both food and air pass through the oropharynx

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17
Q

What is the oesophagus?

A

A muscular tube

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18
Q

What is the function of the oesophagus?

A

It passes food from the pharynx to the stomach

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19
Q

What is the oesophagus continuous with?

A

The lower part of the laryngopharynx

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20
Q

What are the layers of the oesophagus?

A
  • Mucosa
  • Submucosa
  • Muscularis externa
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21
Q

What is the mucosa of the oesophagus composed of?

A
  • Non-keratinised stratified squamous epithelium
  • Lamina propria
  • Layer of smooth muscle (Muscularis Mucosa)
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22
Q

What does the submucosa of the oesophagus contain?

A

The mucous secreting glands

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23
Q

What kind of muscle is in the muscularis externa of the oesophagus?

A
  • Upper third is striated, skeletal muscle, under conscious control
  • Lower two-thirds are smooth muscle, under autonomic control
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24
Q

What is the function of the skeletal muscle in the upper third of the oesophagus?

A

For swallowing

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25
Q

What is the function of the smooth muscle in the lower two thirds of the oesophagus?

A

Peristalsis

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26
Q

How much saliva is produced each day?

A

1.5L

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27
Q

What are the function of saliva?

A
  • Lubricates and wets food
  • Starts digestion of carbohydrates
  • Protects oral environment
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28
Q

How does saliva start the digestion of carbohydrates?

A

Through the presence of amylase

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29
Q

How does saliva protect the oral environment?

A
  • Keeps mucosa moist
  • Washes teeth
  • Maintains alkaline environment
  • High Ca2+ environment
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30
Q

What is the purpose of the alkaline environment maintained by saliva?

A

Neutralises acid produced by bacteria

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31
Q

What is zerostomia?

A

Insufficient saliva production

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32
Q

Can a patient with zerostomia still eat?

A

Yes, providing the food is moist, but teeth and mucosa degrade very quickly

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33
Q

What are the constituents of saliva?

A
  • Water
  • Electrolytes
  • Alkali
  • Bacteriostats
  • Mucus
  • Enzymes
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34
Q

Is saliva hypertonic or hypotonic?

A

Hypotonic

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35
Q

Are the electrolytes in saliva at a higher or lower concentration than plasma?

A
  • Na+ and Cl- usually at lower concentration than plasma
  • Ca2+, K+, and I- are usually at higher concentration than plasma
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36
Q

What makes saliva alkali?

A

HCO3-

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37
Q

Is HCO3- in saliva at higher or lower concentration than in plasma?

A

Higher

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38
Q

What is salivary mucus?

A

A mixure of mucopolysaccharides

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39
Q

What enzymes are in saliva?

A

Salivary amylase

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40
Q

Can we survive without salivary amylase?

A

Yes, it is relatively minor

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41
Q

How many paired salivary glands are there?

A

3

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42
Q

What kind of glands are the salivary?

A

Ducted, exocrine

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43
Q

Describe the structure of salivary exocrine glands

A
  • Made up of acini (blind-ended tubes), lined with acinar cells.
  • The acini are connected via a system of ducts to a single outlet, lined by duct cells
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44
Q

What does the parotid glands secrete?

A

Serous saliva

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45
Q

What is serous saliva?

A

Watery secretion, rich in enzymes, but little mucus

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46
Q

What % of saliva is secreted from the parotid glands?

A

25%

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47
Q

What does sub-lingual glands secrete?

A

Mucus saliva

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48
Q

What is mucus saliva?

A

Viscous secretion, no enzymes but lots of mucus

49
Q

What % of saliva is secreted from the sub-lingual glands?

A

5%

50
Q

What does the sub-maxillary glands secrete?

A

All components of saliva (mixed serous and mucus)

51
Q

Briefly describe the structure of sub-maxillary glands

A

Mixture of serous and mucus acini leading to a common duct

52
Q

What % of saliva is secreted from the sub-maxillary glands?

A

70%

53
Q

Label this diagram

A
  • A - Parotid
  • B - Sub-maxillary
  • C - Sub-lingual
54
Q

What is the cellular mechanism to secrete water?

A

None

55
Q

How is hypotonic saliva secreted?

A

A more concentrated solution is secreted, and solute is then reabsorbed from it to leave the final hypotonic solution

56
Q

What do acinar cells secrete?

A

An isotonic fluid containing enzymes

57
Q

What do duct cells do?

A

Remove Na+ and Cl- from fluid secreted from acinar cells, and add HCO3-

58
Q

How do duct cells ensure that saliva remains hypotonic?

A

The gaps between duct cells are tight, and so water does not follow the osmotic gradient resulting from ion movement

59
Q

What happens at low flow rate of saliva?

Regarding duct cells

A

The duct cells have the opportunity to remove most Na+, so saliva is very hypotonic

60
Q

Can duct cells modify flow rate of saliva?

A

Yes, but their ability to do so is limited

61
Q

What happens at high flow rate of saliva?

Regarding duct cells

A

A smaller fraction of Na+ is removed, and the saliva becomes less hypotonic

62
Q

What does the stimulus for secretion promote?

Regarding ion movement

A

HCO3- secretion, therefore the saliva becomes more alkaline

63
Q

How are Cl- ions secreted from acinar cells?

A

Actively

64
Q

What is the result of the active secretion of Cl- ions from acinar cells into the lumen of the duct?

A

Water and other ions (Na+) will follow passively

65
Q

What transporter has a role in ductal modification?

A

The Na/K-ATPase Antiporter

66
Q

Where is the Na/K-ATPase involved in ductal modification located?

A

In the basolateral membrane of duct cells

67
Q

What is the effect of the Na/K-ATPase antiporter in the duct cell membrane?

A
  • Lowers [Na+] inside the cell. This means there is a concentration gradient, where [Na+] is high in the duct lumen, and low in the duct cells. Na+ diffuses passively back into the duct cells
  • Increases [K+] inside the cell. The resulting concentration gradient drives the expulsion of Cl- form the duct cells into the ECF. A concentration gradient is set up between the duct lumen and cells, with [Cl-] low inside, and [Cl-] high outside. This gradient drives the expulsion of HCO3- into the duct lumen.
68
Q

Draw a diagram illustrating ion transport between the duct and the ECF

A
69
Q

What is salivary secretion controlled by?

A

Mostly the autonomic nervous system

70
Q

What is the effect of parasympathetic stimulation on the salivary gland?

A
  • Increases the production of primary secretion (acinar cells)
  • Increases the addition of HCO3- (duct cells)
71
Q

What is the parasympathetic innervation of the parotid gland?

A
  • Glossopharyngeal nerve (9th cranial nerve)
  • Otic ganglion
72
Q

What is the parasympathetic innervation of the submandibular and sublingual glands?

A
  • Facial nerve (7th cranial nerve)
  • Submandibular ganglion
73
Q

What kind of receptors mediate the parasympathetic innervation of salivary glands?

A

Muscarinic

74
Q

What kind of drugs block the receptors responsible for parasympathetic innervation of the salivary glands?

A

Atropine-like drugs

75
Q

What is the role of co-transmitters in the parasympathetic innervation of the salivary glands?

A

They stimulate extra blood flow

76
Q

What is parasympathetic outflow to the salivary glands mediated by?

A
  • Centres in the medulla
  • Afferent information from the mouth and tongue, nose, and conditioned reflexes
77
Q

What parts of the mouth and tongue mediate parasympathetic outflow to the salivary glands?

A

Taste receptors, especially acid

78
Q

What shows the effect of conditioned reflexes on the outflow to salivary glands?

A

Pavlov’s dogs

79
Q

What is the effect of sympathetic stimulation on the salivary glands?

A

Reduces blood flow, limiting salivary flow and producing the typical dry mouth of anxiety

80
Q

What provides sympathetic innervation to the salivary glands?

A

Superior cervical ganglion

81
Q

What increases the rate of ductal recovery of Na+?

A

The release of aldosterone from the adrenal cortex (increase in ENaC, therefore increase in Na/K-ATPase)

82
Q

What is the result of the increase in ductal recovery of Na+?

A

Makes saliva even more hypotonic

83
Q

What must happen once food has been matiscated and mixed with saliva to form a bolus?

A

It must be swallowed

84
Q

What are the phases of swallowing?

A
  1. Voluntary phase
  2. Pharyngeal phase
  3. Oesophageal phase
85
Q

What happens during the voluntary phase of swallowing?

A

Tongue moves the bolus back onto the pharynx

86
Q

What happens during the pharyngeal phase of swallowing?

A
  • Afferent information from pressure receptors in the palate and anterior pharynx reaches the swallowing centre of the brain stem
  • A set of movements is triggered
87
Q

What movements are inhibited in the pharyngeal phase of swallowing?

A
  • Inhibition of breathing
  • Raising of the larynx
  • Closure of the glottis
  • Opening of the upper oesophageal ‘sphincter’
88
Q

What kind of muscle is found in the upper third of the oesophagus, and what kind of control is it under?

A
  • Striated muscle
  • Under voluntary, somatic control
89
Q

What kind of muscle is found in the lower two thirds of the oesophagus, and what kind of control is it under?

A
  • Smooth muscle
  • Parasympathetic control
90
Q

What happens in the oesophageal phase of swallowing?

A

A wave of peristalsis sweeps down the oesophagus, propelling the bolus to the stomach

91
Q

How long does the oesophageal phase take to propel the food bolus to the stomach?

A

~9 seconds

92
Q

What is the oesophageal phase of swallowing coordinated by?

A

Extrinsic nerves from the swallowing centre of the brain

93
Q

What happens once the food bolus has been propelled to the stomach by the oesophageal phase?

A

The lower oesophageal ‘sphincter’ opens

94
Q

What is dysphagia?

A

The symptom of difficulty in swallowing

95
Q

What is odynophagia?

A

The symptom of pain whilst swallowing

96
Q

What may dysphagia be a consequence of?

A
  • A primary oesophageal disorder
  • A secondary consequence of another tissue
97
Q

Give an example of a primary oesophageal disorder causing dysphagia?

A

Achalasia

98
Q

What is achalasia?

A

Motility problems of the smooth muscle preventing peristalsis

99
Q

Give an example of a secondary condition that may cause dysphagia?

A

Obstruction or compression of the oesophagus due to a tumour

100
Q

Broadly speaking, what can dysphagia be split into?

A
  • Dysphagia for solids
  • Dysphagia for liquids
101
Q

What is dysphagia for solids called?

A

Oesophageal dysphagia

102
Q

How is oesophageal dysphagia investigated?

A

Barium swallow or endoscopy

103
Q

What is dysphagia for liquids called?

A

Oropharyngeal dysphagia

104
Q

How is oropharyngeal dysphagia investigated?

A

A flexible endoscopy evaluation of swallowing

105
Q

What does a flexible endoscopy evaluation of swallowing allow?

A

For you to view the entire trachea/oesophagus

106
Q

What is oropharyngeal dysphagia most commonly due to?

A

Stroke

107
Q

What does the stomach produce to aid the digestion of food?

A
  • Strong acids (HCl)
  • Enzymes (pepsin)
108
Q

What protects the stomach from its potentially harmful products?

A

The mucosa of the stomach

109
Q

How is the oesophagus protected from the potentially harmful products of the stomach?

A

By a one way valve mechanism at it’s junction with the stomach

Does not have the mucosal protection that the stomach does

110
Q

What is the one way valve protecting the oesophagus from stomach products called?

A

The lower oesophageal sphincter

111
Q

What is the lower oesophageal sphincter coupled with?

A

The angle of His, which is formed at this point

112
Q

What does the lower oesophageal sphincter and the angle of His work together to do?

A

Prevent the contents of the stomach refluxing back into the oesophagus

113
Q

What does the crus of the diaphragm do?

A

Helps with the sphincteric action

114
Q

What are the clinical consequences of free gastro-oesophageal reflux?

A
  • Barrett’s Oesophagus
  • Gastro-oesophageal reflux disease (GORD)
115
Q

What is Barrett’s Oesophagus?

A

An abnormal change in epithelial cells of the oesophagus

116
Q

What is the pathological process in Barrett’s Oesophagus?

A

This is a metaplasia from non-keratinised stratified squamous epithelia to columnar epithelium and goblet cells.

This is an attempt to better resist the harmful contents of the stomach

117
Q

What is Barrett’s oesophagus strongly associated with?

A

Adenocarcinoma, a particularly lethal cancer

118
Q

What happens in GORD?

A

The reflex of the stomach’s contents into the oesophagus and pharynx causes several symptoms, including;

  • Cough
  • Hoarseness
  • Asthma

All symptoms result from the acidic contents of the stomach refluxing back out

ESA 3 - Gastrointestinal System (12 decks)

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