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Semester 3 - Gastrointestinal > Session 2 - Saliva and the Salivary glands > Flashcards

Session 2 - Saliva and the Salivary glands Flashcards

1
Q

What structures facilitate mastication?

A
  • Teeth

* Muscles of mastication

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2
Q

What is the purpose of the teeth?

A
  • Cut (incisors)
  • Crush (molars)
  • Mix with saliva
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3
Q

What are the muscles of mastication?

A
  • Masseter

* Innervated by branch of trigeminal nerve

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4
Q

How many litres of saliva produced per day?

A

1.5

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5
Q

What are the functions of saliva?

A
  • Lubricates and wets food
  • Starts digestion of carbohydrate
  • Protects oral environment
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6
Q

Give four ways saliva protects the oral environment?

A 
• Keeps mucosa moist 
• Washes teeth
• Maintains alkaline environment
	○ Neutralises acid produced by bacteria
• High calcium concentration (?)
	○ Soluble in acidic solution, not in alkaline and thus do not degrade
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7
Q

What is the condition when you do not have enough saliva, and what occurs?

A
  • Zerostomia (stomeeyah)

* Can still eat food, but teeth and mucosa degrade very quickly

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8
Q

What is the tongue?

A

A collection of 8 muscles that work to manipulate food for mastication and form it into a bolus

Aids in swallowing

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9
Q

What are the six main constituents of saliva?

A 
• Water
• Electrolytes
• Alkali
• Bacteriostats
• Mucus
	○ Mixture of mucopolysaccharides
• Enzymes - Salivary amylase
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10
Q

What is meant by “hypotonic” water?

A

• More water in saliva than in rest of body (osmotic potential body –> saliva)

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11
Q

How does the concentration of Na+ and Cl- in the saliva compare to that in the plasma?

A

• Lower concentration in saliva

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12
Q

How does concentration of Ca2+, K+ and I- in saliva compare to plasma?

A

• High concentration in saliva as compared to plasma
○ K+ as by product from production of saliva
○ I- helps control population of bacteria

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13
Q

What makes saliva alkaline?

A

• The addition of HCO3

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14
Q

What are the three paired salivary glands?

A
  • Parotid
  • Sub Mandibular
  • Sub-lingual
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15
Q

What is the structure of the salivary glands?

A

• Ducted, exocrine glands

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16
Q

What are ducted exocrine glands made up of?

A
  • Blind ended tubes

* Connected system of ducts

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17
Q

What cells line the acini, or the blind ended part of the salivary glands?

A

• Acinar cells

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18
Q

What cells line the ducts of the salivary glands

A

• Duct cells

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19
Q

What kind of secretion is produced by the parotid?

A
  • Watery secretion rich in enzymes, but little mucus (serous)
    • 25%
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20
Q

What types of secretions are produced by the sublingual glands?

A
  • Viscous secretion
  • No enzymes
  • Lots of mucus
  • 5%
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21
Q

What secretion are produced by the sub-maxillary glands?

A
  • All components of saliva, mix serous and mucous
  • Gland made up of mixture of serous and mucous acini, leading to common ducts
  • 70% of all saliva
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22
Q

How is saliva produced to be hypotonic, despite being made form extra-cellular fluid

A

• Glands secrete more concentrated solution and remove solute

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23
Q

Why isn’t saliva secreted directly in its final state?

A

• No cellular mechanism to secrete water

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24
Q

How is saliva secreted?

A

• Ïn a concentrated substance, from which solute is reabsorbed

25
Q

What do acinar cells secrete?

A

• An isotonic fluid containing enzymes

26
Q

What do duct cells do to pre-saliva?

A
  • Remove Na+ and Cl-

* Add HCO3-

27
Q

Why does water not follow the electrolytes removed from saliva by the duct cells

A

• Gaps between duct cells very tight

28
Q

Why is saliva more concentrated at a higher flow rate?

A

• Duct cells have a limit on how much Na+ and Cl- they can remove
Smaller fraction removed

29
Q

What happens to the pH of saliva at higher flow rates?

A
  • Stimulus for secretion promotes HCO3- secretion

* Saliva becomes more alkaline

30
Q

Outline the mechanism of acinar secretion

A
  • Cl- actively secreted into lumen of cut

* Water and other ions then follow passively

31
Q

How do the duct cells remove Na+ from the lumen of the duct?

A
  • Na+/K+-ATPase antiporter on ECF membrane secretes Na+ out of cell
  • This generates conc gradient from Na+ from duct lumen to duct cell
32
Q

How do the duct cells remove Cl- from the lumen?

A
  • Na/K+-ATPase also increases conc of K+ within the cell
  • This drives expulsion of Cl- into the ECF via a K+/Cl- symport transporter
  • Cl- high in lumen, low in cell. Conc grad, diffusion
33
Q

How is HCO3- secreted into the duct lumen?

A
  • Cl-/HCO3- antiporter

* Cl- moves into cell down conc grad, HCO3- moves into lumen

34
Q

What part of the nervous system controls salivary secretion?

A

• Autonomic nervous system

35
Q

What does parasympathetic stimulation of the salivary glands do?

A

• Increases production of primary secretion and increases addition of HCO3

36
Q

Outline the pathway of parasympathetic stimulation of salivary glands

A

o Parotid Gland
 Glossopharyngeal Nerve (9th cranial nerve)
 Otic ganglion

o Submandibular and Sublingual Glands
 Facial Nerve (7th cranial nerve)
 Submandibular ganglion

o Muscarinic receptors
 Blocked by atropine like drugs
o Co-transmitters stimulate extra blood flow

37
Q

Outline the parasympathetic outflow surrounding saliva stimulation

A 
• Afferent information from
	○ Mouth and tounge - taste receptors
	○ Nose 
	○ Conditioned reflexes
• All goes to medulla
38
Q

Outline sympathetic stimulation of salivary glands?

A

• Occurs via superior cervical ganglion
○ Reduces blood flow to the salivary glands
○ Limits salivary flow

39
Q

Where is the oropharynx found?

A
  • Behind the oral cavity
  • Below the nasopharynx
  • Above the laryngopharynx
40
Q

From what structures does the oropharynx extend to and from?

A

• The uvula to the hyoid bone

41
Q

What structure closes over the glottis to prevent aspiration?

A

• The epiglottis

42
Q

What is the oesophagus?

A
  • A muscular tube that passes food from the pharynx to the stomach
  • Continuous with the lower part of the laryngopharynx
43
Q

Outline the tissue structure of the oesophagus

A

• Mucosa
○ Composed of non-keratinized stratified squamous epithelium, lamina propria and a layer of smooth muscle
• Submucosa
○ Containing mucous secreting glands
• Muscularis externa
○ Upper third of oesophagus has striated skeletal muscle under somatic control for swallowing
○ Lower two thirds are smooth muscle under autonomic control

44
Q

What does the brain stem swallowing centre do when pressure felt of pharyngeal plate

A
  • Inhibits respiration
  • Raises larynx
  • Closes the glottis
  • Can open upper oesophageal sphincter
45
Q

What are the three phases of swallowing?

A
  • Voluntary phase
  • Pharyngeal phase
  • Oesophageal phase
46
Q

What happens in the voluntary phase of swallowing?

A

• Tongue moves bolus back onto the pharynx

47
Q

What happens in the pharyngeal phase of swallowing?

A
  • Afferent information from pressure receptors in the palate and anterior pharynx reaches the swallowing centre in the brain stem.
  • A set of movements is triggered
  • Inhibition of breathing
  • Raising of the larynx
  • Closure of the glottis
  • Opening of the upper oesophageal ‘sphincter’
48
Q

What happens in the oesophageal phase of swallowing?

A
  • The muscle in the upper third of the oesophagus is voluntary striated muscle under somatic control
  • The muscle of the lower two thirds is smooth muscle under control of the parasympathetic nervous system.
  • A wave of peristalsis sweeps down the oesophagus, propelling the bolus to the stomach in ~9 seconds.
  • Coordinated by extrinsic nerves from the swallowing centre of the brain
  • Lower oesophageal ‘sphincter’ opens
49
Q

What is dysphagia?

A

• The symptom of difficulty in swallowing

50
Q

What is odynophagia

A

• The symptom of pain whilst swallowing

51
Q

What is achalasia?

A
  • Motility problems of the smooth muscle preventing peristalsis
  • Caused by damage and loss of nerves in gullet wall
52
Q

What are the two main types of dysphagia?

A
  • Oesophageal dysphagia

* Oropharyngeal dysphagia

53
Q

What is oesophageal dysphagia and how is it investigated?

A
  • Dysphagia for solids

* Investigate with barium swallow/endoscopy

54
Q

What Oropharyngeal dysphagia?

A

• Investigate with a flexible endoscopy evaluation of swallowing, allowing you to view entire trachea

55
Q

What causes dysphagia?

A

• Obstruction or compression of oesophagus

- Tumours

56
Q

What is Barrett’s oesophagus?

A
  • An abnormal change of the epithelial cells of the oesophagus
  • Metaplasia from non-keratinised stratified squamous epithelia to columnar epithelium and goblet cells
  • Strong association with adenocarcinoma
57
Q

What is gastro-oesophageal reflux disease?

A

• Reflux of stomach’s content’s into the oesophagus and pharynx causes cough, hoarseness and asthma

58
Q

Why does gastro-oesophageal reflux damage the oesophagus?

A

• Does not have the same protective mucosa as the stomach

59
Q

What features protect the oesophagus from reflux?

A
  • The lower oesophageal sphincter
  • Angle of his (acute angle of entry of oesophagus
  • Positive intra-abdominal pressure compresses the oesophagus

Semester 3 - Gastrointestinal (28 decks)

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