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GI physiology peer teaching Flashcards

1
Q

What are the functions of saliva?

A

lubricant
Maintaining oral pH (pH 6.2-7.4)
Begin starch digestion
anti bacterial

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2
Q

Describe serous saliva

A

Rich in enzymes ( water and alpha amylase)

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3
Q

Describe mucous saliva

A

mucins for lubrication

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4
Q

What type of saliva do the parotid glands secrete?

A

Serous

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5
Q

What type of saliva do the sublingual glands secrete?

A

mucous

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6
Q

What type of saliva do the submandibular glands secrete?

A

mixed

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7
Q

Which major salivary glands have only serous secretions?

A

parotid

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8
Q

Which major salivary glands have only mucous secretions?

A

Sublingual

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9
Q

Minor glands mostly secrete what type of saliva?

A

mucous

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10
Q

Name the only serous minor salivary gland?

A

Von Ebner’s

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11
Q

What is cranial nerve IX?

A

glossopharngeal

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12
Q

The parotid gland receives parasympathetic fibres from which cranial nerve?

A

glossopharngeal (IX)

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13
Q

What is cranial nerve VII?

A

facial nerve

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14
Q

Which salivary glands receive parasympathetic fibres from the facial nerve?

A

Submandibular

Sublingual

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15
Q

What are the secretory cells in the salivary glands ?

A

acinar cells

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16
Q

In the salivary glands, what type of duct connects the acini to striated ducts?

A

Intercalated ducts

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17
Q

What is secreted in the striated ducts of salivary glands?

A

HCO3- and K+

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18
Q

What is absorbed in the striated ducts of salivary glands?

A

Na+ and Cl-

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19
Q

In the salivary glands, what comes after the striated ducts?

A

Interlobar ducts

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20
Q

What type of cell secretes mucous in the stomach?

A

mucous cells

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21
Q

What do parietal cells secrete?

A

gastric acid and intrinsic factor

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22
Q

what type of cell secretes pepsinogen?

A

cheif cells

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23
Q

What do G cells secrete?

A

gastrin

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24
Q

What type of cell in the stomach secretes somatostatin?

A

D cells

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25
Q

What type of cells in the stomach secrete histamine ?

A

Enterochromaffin like cells (ECL cells)

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26
Q

What effect does somatostatin have on HCL secretion?

A

inhibits HCL secretion

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27
Q

What effect does histamine have on HCL secretion?

A

stimulates HCL secretion

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28
Q

What effect does Gastrin have on HCL secretion

A

stimulates HCL secretion

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29
Q

Which two ions passively diffuse into the gastric lumen from parietal cells?

A

Cl- and K+

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30
Q

Where do the H+ ions come from that form stomach acid?

A

The H+ ions pumped into the gastric lumen come from water.

31
Q

How is water, used as a proton source, replenished in the parietal cells?

A

water is replenished by getting H+ from H2CO3 that results from the reaction of the H2O and CO2 produced in cellular respiration.
H2O + CO2 >H2CO3
H2CO3 > H+ + HCO3-
H+ + OH- = H2O

32
Q

What is the enzyme involved in the conversion of H2O and CO2 into carbonic acid?

A

carbonic anhydrase

33
Q

What happens to the waste HCO3- that results from gastric acid secretion?

A

HCO3- moves into the blood and is swapped for Cl-

34
Q

What type of pump will you find on the luminal surface of parietal cells?

A

hydrogen potassium ATPase

35
Q

Describe how the balance of potassium is maintained in a parietal cell?

A

K+ diffuses out when Cl- diffuses out

K+ is replaced by hydrogen potassium ATPase

36
Q

Is the secretion of stomach acid an active process?

A

Yes

37
Q

What are the two phases in which gastric acid secretion is turned on?

A

The cephalic phase

The gastric phase

38
Q

Describe the cephalic phase (ON)

A

The thought, smell or taste of food results in….
Parasympathetic activity to the stomach via the vagus nerve
Ach released
Ach acts directly on parietal cells
Ach triggers release of gastrin and histamine
Gastrin and histamine act directly on parietal cells
All this increases stomach acid production

39
Q

Parasympathetic activity to the stomach travels via which nerve?

A

the vagus nerve

40
Q

What is the parasympathetic nerurotransmitter?

A

Ach

41
Q

What does Ach trigger the release of?

A

gastrin and histamine

42
Q

Describe the gastric phase (ON)

A

Gastric distension and the presence of peptides and amino acids trigger gastrin release
gastrin acts directly on parietal cells
gastrin triggers histamine release
histamine acts directly on parietal cells
All this increases stomach acid production

43
Q

How does a the presence of protein in the stomach disinhibit gastric acid secretion?

A

The protein mops up H+
This causes the pH to rise
Increased pH reduces somatostatin secretion (somatostatin inhibits HCl secretion)

44
Q

Describe the gastric phase OFF

A

low luminal pH
Directly inhibits gastrin secretion
Indirectly inhibits histamine secretion (by inhibiting gastrin)
Stimulates somatostatin release which inhibits HCl secretion

45
Q

Describe the intestinal phase OFF

A

In the duodenum:
Distension, low luminal pH, hypertonic luminal contents and the prescence of amino acids and fatty acids
The duodenum detects these changes and secretes secretin and cholecystokinin (CCK)
CCK and secretin act directly on the stomach to inhibit gastrin release and promote somatostatin release

Furthermore
The presence of food in the deodenum activates neural pathways
The long neural pathway:
Via the vagus nerve to the brain
Down regulates parasympathetic activity and upregulates sympathetic activity
this reduces ACh in the stomach
The short neural pathways:
Go directly from the duodenum to the stomach
Reduce ACh release

46
Q

What are enterogastrones?

A

Hormones secreted by the duodenum

47
Q

Give examples of enterogastrones

A

secretin

CCK

48
Q

What effect do secretin and CCK have on gastrin?

A

inhibit gastrin release

49
Q

What effect do secretin and CCK have on somatostatin?

A

promote somatostain release

50
Q

What is an ulcer?

A

a breach in a mucosal surface

51
Q

How does the gastric mucosa defend against acid?

A

Secreting alkaline mucous
Tight junctions between epithelial cells
Active population of stem cells at base of gastric glands
Negative feedback loops- turning off HCl secretion

52
Q

What type of drugs reduce mucosal defence?

A

NSAIDS

53
Q

What are enterogastrones?

A

Hormones secreted by the duodenum

54
Q

Give examples of enterogastrones

A

secretin

CCK

55
Q

What effect do secretin and CCK have on gastrin?

A

inhibit gastrin release

56
Q

What effect do secretin and CCK have on somatostatin?

A

promote somatostain release

57
Q

What is an ulcer?

A

a breach in a mucosal surface

58
Q

How does the gastric mucosa defend against acid?

A

Secreting alkaline mucous
Tight junctions between epithelial cells
Active population of stem cells at base of gastric glands
Negative feedback loops- turning off HCl secretion

59
Q

What type of drugs reduce mucosal defence?

A

NSAIDS

60
Q

What are the stimuli for pepsinogen proctuction?

A

The same as the stimuli for HCl secretion

61
Q

What can convert pepsinogen into pepsin?

A

Initially HCl

once pepsin is present, pepsin becomes the main factor

62
Q

at what pH is the conversion of pepsinogen to pepsin most efficiant?

A

pH less than 2

63
Q

What percentage of all protein digestion does pepsin usually account for?

A

20%

64
Q

What volume can the stomach hold?

A

1.5L

65
Q

Which anal sphincter is voluntary and which is involuntary?

A

The internal anal sphincter is a continuation of the smooth muscle of the colon- It is involuntary
The external anal sphincter is formed from the plevic floor . It is under voluntary control

66
Q

Which cells regulate peristalsis ?

A

Interstitial cells of cajal

67
Q

What increases the strength of the peristaltic contractions of the stomach?

A

gastrin

gastric distension

68
Q

What decreases the strength of the peristaltic contractions of the stomach?

A 
duodenal distension 
increased duodenal luminal fat 
increased duodenal osmolarity ( due to increased amino acids in the lumen)
Decreased luminal pH
Increased sympathetic action
Decreased parasympathetic action
69
Q

How does digestion occur in the colon?

A

via bacteria

70
Q

Digestion of material by bacteria in the colon allows release of which vitamins?

A

K and B

71
Q

What is the gastro-colic reflex?

A

Stomach distention and food in the jejunum causes mass movement of the colon

72
Q

Which anal sphincter is voluntary and which is involuntary?

A

The internal anal sphincter is a continuation of the smooth muscle of the colon- It is involuntary
The external anal sphincter is formed from the plevic floor . It is unde r

73
Q

Describe the state of both the anal sphincters and the puborectalis muscle when the rectum is empty

A

All contracted

GI (11 decks)

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