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Phase 1 > Gastrointestinal > Flashcards

Gastrointestinal Flashcards

1
Q

What are the 4 functions of saliva?

A
  • Lubricant for mastication, swallowing and speech
  • Oral hygiene - wash, buffer and immunity (antiviral/bacterial/fungal)
  • Maintains oral pH at about 7.2 (bicarbonate/carbonate buffer system)
  • Digestive enzymes - aqueous solvent necessary for taste
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2
Q

What is the typical flow rate of saliva?

A

0.3 - 7 ml/minute

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3
Q

What is the typical daily secretion of saliva?

A

800 - 1500 ml in adults

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4
Q

What factors affect the composition and amount of saliva produced?

A
  • Flow rate
  • Circadian rhythm
  • Type and size of gland
  • Duration and type of stimulus
  • Diet
  • Drugs
  • Age
  • Gender
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5
Q

What are the three major glands and what do they secrete?

A
  • Parotid - just serous
  • Submandibula - both serous and mucous
  • Sublingular - mainly mucous, some serous
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6
Q

What is secreted in serous fluid?

A

Alpha amylase - used for starch digestion

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7
Q

What is secreted in mucous fluid?

A

Mucins for lubrication of mucosal surfaces

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8
Q

What is saliva?

A

A secretion of proteins and glycoproteins in a buffered electrolyte solution

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9
Q

What glands are continuously active?

A
  • submandibular
  • sublingual
  • minor glands
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10
Q

When does the parotid gland secrete saliva?

A
  • no secretion when unstimulated
  • main source of saliva when stimulated
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11
Q

What is whole saliva?

A
  • Salivary gland secretions
  • Blood
  • Oral tissues
  • Microorganisms
  • Food remnants
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12
Q

What defends the oral cavity?

A

> Mucosa - physical barrier
Palatine tonsils - surveillance system for the immune system
Salivary glands - washes away food particles bacteria/viruses might use for metabolic support

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13
Q

How do the salivary glands aid immunity?

A

> Surrounded by lymphatic system - linked to thoracic duct and blood
Broad range of functional immune cells
Oral mucosa and glands have a high blood flow rate

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14
Q

What is the main component of unstimulated saliva?

A

submandibular gland secretion

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15
Q

What is the main component of stimulated saliva?

A

parotid gland secretion

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16
Q

What common illnesses can now be diagnosed using saliva testing?

A

cystic fibrosis
tuberculosis

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17
Q

What two tissues compose salivary glands?

A

> duct cells - collect to form large ducts entering the mouth, equipped with channel transporters (surrounded by acinar cells)
acinar cells - functional unit of gland

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18
Q

What do serous acini look like on a histology slide?

A
  • dark stained
  • nucleus in the basal third
  • small central duct
  • secrete water and alpha amylase
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19
Q

What do mucous acini look like on a histology slide?

A
  • pale staining (foamy)
  • nucleus at base of cell
  • large central duct
  • secrete mucous (water and glycoproteins)
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20
Q

Intralobular ducts divide into what?

A

intercalated
striated

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21
Q

What are intercalated ducts?

A
  • short narrow duct segments with cuboidal cells that connect acini to larger striated ducts
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22
Q

What are striated ducts?

A
  • striated like a thick lawn
  • major site for the reabsorption of NaCl
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23
Q

What do striated ducts look like on a histology slide?

A
  • appear striated at the basal end
  • basal membrane highly folded into microvilli for active transport of HCO3 against concentration gradient
  • microvilli filled with mitochondria for energy to facilitate active transport
24
Q

How do ducts modify the electrolyte composition of saliva?

A

> ducts secrete K+ and HCO3-
ducts reabsorb Na+ and Cl-
epithelium doesn’t allow water movement so final saliva is hypotonic

25
Q

What percentage of salivary flow do the three main glands contribute to?

A

80%

26
Q

What percentage of salivary flow do the minor glands contribute to?

A

20%

27
Q

Where are the minor glands found?

A

submucosa or oral mucosa of the lips, cheeks, hard and soft plate and the tongue

28
Q

Where is the parotid gland found?

A

Superficial triangle between the:
- zygomatic arch
- sternocleidomastoid
- ramus of mandible

29
Q

Where does the parotid duct run through?

A

(also called Stenson’s duct)
- crosses the masseter muscle
- pierces through buccinator muscle
- can be palpated a fingers breadth below the zygomatic arch

30
Q

How is the parotid gland innervated?

A

> sympathetic sensory innervation (inhibits secretion) from the auriculo-temporal nerve
parasympathetic innervation (stimulates secretion) from the glossopharyngeal nerve (IX)

31
Q

What structures pass through the parotid?

A
  • External carotid artery
  • Retromandibular vein
  • Facial nerve (VII) - supplies muscles of facial expression
32
Q

Is the parotid capsule tough or soft?

A

Tough (to protect its contents)

33
Q

What is the shape of the lobes of the submandibular glands?

A
  • Larger superficial lobe
  • Smaller deep lobe in the floor of the mouth
34
Q

What is another name for the submandibular duct?

A

Wharton’s duct

35
Q

What is the course of the submandibular duct?

A
  • begins in superficial lobe
  • wraps around free posterior border of mylohyoid
  • runs along floor of mouth
  • empties into the oral cavity at sublingual papillae
36
Q

How are the submandibular glands innervated?

A

> sympathetic innervation from chorda tympani brach of the facial nerve (VII)
parasympathetic innervation from lingual nerve (derived from facial nerve)
very similar to sublingual

37
Q

Where are the sublingual glands positioned?

A

Between the mylohyoid muscle and oral mucosa of the floor of the mouth
Very close to the submandibular gland

38
Q

How is saliva from the sublingual glands transmitted?

A
  • via Wharton’s (submandibular) duct
  • or small ducts that pierce the oral mucosa on the floor of the mouth
39
Q

What are bigger the submandibular or sublingual glands?

A

Submandibular glands are larger but size is variable

40
Q

How are the sublingual glands innervated?

A

> sympathetic innervation from chorda tympani branch of the facial nerve (VII)
parasympathetic innervation from the lingual nerve (derived from facial nerve)
very similar to submandibular

41
Q

What regions are the minor salivary glands concentrated?

A
  • buccal labial
  • palatal
  • lingual
42
Q

What do the minor salivary glands secrete?

A

> ALL mucous
APART from serous glands of von Ebner (underlying circumvallate papillae)

43
Q

How do minor glands drain?

A

They lack a branching network of ducts
Each salivary unit has its own simple duct

44
Q

What is the medical name for dry mouth?

A

Xerostomia

45
Q

What are the most common causes of xerostomia?

A
  • consequence of cystic fibrosis
  • consequence of Sjorgren’s syndrome (autoimmune attacking glands)
  • drug side effects
  • side effect of irradiation for head/neck cancers
46
Q

What is a common cause of obstruction in the salivary glands?

A

> Saliva contains calcium and phosphate ions that can form salivary calculi (stones)
Most often in the submandibular gland (c 80%)
Often blocks the duct at the bend around the mylohyoid, or exit at sublingual papillae

47
Q

What is the cause of inflammation of the salivary glands?

A

Infection secondary to blockage

48
Q

How low does salivary output have to be to be classed as xerostomia?

A

less than 50% of normal flow

49
Q

What are the effects of salivary gland dysfunction?

A

> low lubrication - oral function difficult
low (natural) oral hygiene - poor pH control, accumulation of plaque, opportunistic infections

50
Q

What are the functions of the stomach?

A
  • store and mix food
  • dissolve and continue digestion
  • regulate emptying into duodenum
  • kill microbes
  • secrete intrinsic factor and proteases
  • activate proteases
  • lubrication
  • mucosal protection
51
Q

What are the 6 key cells types?

A

Mucous cells - produce mucous, at entrance to gland
Parietal cells - produce HCl and intrinsic factor
Chief cells - produce pepsinogen
Enterochromaffin-like (ECL) cells - releases histamine
G cells - releases gastrin
D cells - releases somatostatin

52
Q

Approximately how much gastric acid is secreted a day?

A

Approx. 2 Litres

53
Q

What is the main component of gastric acid?

A

Hydrochloric acid

54
Q

What is the secretion of gastric acid dependant on?

A

Energy dependant (goes against the concentration gradient)
Regulated by neural and humoral factors (nerves + hormones)

55
Q

Turning on gastric acid secretion - Cephalic phase

A

Regulated by the sympathetic nervous system
- sight, smell, taste of food, chewing -> causes acetylcholine (ACh) release
- ACh acts directly on parietal cells -> triggers release of gastrin & histamine

net effect = increase acid production

56
Q

Turning on gastric acid secretion - Gastric phase

A
  • gastric distention, presence of peptides an amino acids -> causes gastrin release
  • gastrin acts directly on parietal cells -> triggers the release of histamine which acts directly on parietal cells

net effect = increased acid production

Phase 1 (4 decks)

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