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Case 3 > Physiology Upper GI > Flashcards

Physiology Upper GI Flashcards

1
Q

How is saliva formed?

A
  1. Formed in acinus
  2. Modified as it flows down ducts (Cl- exchanged for HCO3-, Na+ exchanged for K+)

Ducts IMPERMEABLE to H2O
PS activity increases secretion rate

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2
Q

What affect does the stimulation of saliva do to its composition?

A

High secretion rate = less time to remove Na & Cl so their conc increases

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3
Q

What happens in the oral phase of swallowing?

A

Voluntary

Tongue stimulates mechanoreceptors in hard palate

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4
Q

What happens in the pharyngeal phase of swallowing?

A

Involuntary

Larynx rises, epiglottis closes entrance to trachea = deglutition apnea = temporary inhibition respiratory ventilation

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5
Q

What happens in the oesophageal phase of swallowing?

A

Receptive relaxation ahead of bolus
Vagovagal reflex
Upper 1/3 = striated = brainstem control
Lower 2/3 = smooth muscle = ENS control

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6
Q

What do G cells release?

A

Gastrin

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7
Q

What do D cells release?

A

Somatostatin

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8
Q

What so H cells release?

A

Histamine

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9
Q

What do cheif cells release?

A

Pepsinogen

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10
Q

What do parietal cells release?

A

HCL

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11
Q

What is the effect of excessive alcohol on mucus production?

A

= Excess mucus production = ulceration as protective effect of HCO3- limited

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12
Q

What happens when parietal cells are at rest?

A

Proton pumps in tubulovesicles of cells - locked away -> Quiescent

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13
Q

What happens when parietal cells are stimulated?

A

Proton pumps activates as tubulovesicles fuse with apical membrane -> enlarging cannaliculus
H/K/ATPase in vesicle membranes

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14
Q

How is HCL secreted?

A

Ionisation of water = H+
H/K/ATPase pump in apical membrane
HCO3- exchanged with Cl- in basolateral membrane

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15
Q

What happens in the cephalic phase of digestion?

A
  • stimulated by sight, smell, taste
  • secretion of ACh
  • G cells secrete gastrin = parietal cells release HCL, Cheif cells release pepsinogen
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16
Q

What happens in the gastric phase of digestion?

A
  • due to stomach distention
  • vagovagal reflex = ACh secretion
  • low pH INHIBITS gastric secretion (somatostatin released from D cells)
17
Q

What happens in the intestinal phase of digestion?

A
  • stimulated by protein digestion
  • duodenal release of gastrin (= response to increased protein digestion) -> STIMULATORY
  • duodenal release of secretin (= response to increased acid) + CCK + GIP (= response to increased fat digestion) -> INHIBITORY
18
Q

What effect does histamine have on parietal cells?

A

Potentiates effect of gastrin = HCL secretion

19
Q

What effect does somatostatin have on parietal cells?

A

Switches off HCL secretion

20
Q

What effect does prostaglandin have on parietal cells?

A

Helps keep HCL secretion switched off

21
Q

What effect do fats have on gastric emptying?

A

Inhibitory

22
Q

What neural feedback control switches off acid secretion?

A

Withdrawal of vagal activity and increase in splanchnic nerve activity (sympathetic)

23
Q

What effect do enterogastrones have on gastrin secretion?

A

Inhibitory

Released from small intestine

24
Q

How is gastrin secretion inhibited in the gastric phase?

A

low pH - H+ acts on D cells = increased inhibitory effects of Somatostatin on G cells = reduces gastrin release

25
Q

What enterogastrone enters the intestinal phase in response to FA’s?

A

GIP released by K cells - inhibits gastric secretion

CCK released by I cells (also response to AA’s)

26
Q

What enterogastrone enters the intestinal phase in response to H+?

A

Secretin released by S cells - stimulates D cells to release somatostatin…

27
Q

What is the key difference between pancreatic and saliva secretion?

A

Ducts in pancreatic acinus = PERMEABLE to H2O

28
Q

Where are Acinar cells and what is their function?

A

Pancreas
Secrete enzymes + Cl- rich sol
Stimulated by CCK + ACh

29
Q

Where are Duct cells and what is their function?

A

Pancreas
Secrete HCO3- rich sol
Stimulated by secretin

30
Q

How do Duct cells modify acinar secretion?

A

Using Carbonic hydrase, apical HCO3/Cl exchange + basolateral Na/H exchange

31
Q

What are Duct cell agonists and how do they work?

A

Secretin & ACh - stimulate HCO3/Cl exchange

32
Q

What happens in the cephalic stage of pancreatic secretion?

A

Duct cells + Acinar cells activated via PS vagal efferent nerves

33
Q

What happens in the gastric stage of pancreatic secretion?

A
  • Acinar stimulated via gastrin

- Acinar + Duct stimulates via vagovagal reflex

34
Q

What happens in the intestinal stage of pancreatic secretion?

A
  • Acinar (CCK) release enzyme rich

- Duct (secretin) release bicarb rich

35
Q

What effects does CCK have on the gallblader and sphincter of oddi?

A

Contracts GB and relaxes sphincter

36
Q

What are the 2 mechanisms of bile secretion?

A

BAD-bile acid dependent 1 - depends on rate of bile return

BAI-bile acid independent 2 - depends on secretion of electrolytes + water

37
Q

What effects do choleretics and cholagogues have on bile secretion?

A

Increase rate of bile secretion

Case 3 (9 decks)

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