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GI Final > Secretions of GI Tract + Pancreas > Flashcards

Secretions of GI Tract + Pancreas Flashcards

1
Q

What is the function of saliva?

A
  1. Initial digestion of starches + lipids
  2. Dilution + buffering of ingested food
  3. Lubrication of ingested food w/ mucus

Saliva = hypotonic

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2
Q

What are the 3 types of salivary glands?

A
  1. Parotid (serous)
  2. Submaxillary + Sublingual (serous + mucous)
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3
Q

What does the acinus do?

A

(1st step) Secrete inital saliva

Isotonic

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4
Q

What do myoepithelial cells of salivary glands do?

A

Contract to eject salvia into mouth

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5
Q

What do ductal cells do?

A

(2nd step) Modify the initial saliva to produce the final (hypotonic) saliva

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6
Q

How does saliva become hypotonic as it flowss through the ducts?

A

Ductal cells are impermeable to H20

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7
Q

What is in high concentration in saliva?

A

K+ and HCO3 (low Na+ and Cl-)

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8
Q

What 3 transport mechanisms are on the blood (basolateral) side of a salivary ductal cell?

A
  1. Na+/K+ ATPase
  2. Cl- channels
  3. Sodium-bicarb transport
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9
Q

What 3 mechanisms are on the lumen side of a salivary ductal cell?

A
  1. Na+/H+ exchange
  2. Cl-/HCO3- exchange
  3. H+/K+ exchange
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10
Q

Through the mechanisms of salivary secretion what is the net outcome?

A

There is net absorption of solute!

(more NaCl absorbed than KHCO3 secreted)

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11
Q

What 2 nerves are innervated by salivary glands and under parasympathetic control?

A

Facial N.

Glossopharyngeal N.

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12
Q

What glands does the facial N. innervate?

A

Submandibular + sublingual glands

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13
Q

What glands does the glossophayngeal N. innervate?

A

Parotid gland

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14
Q

What nerve is under sympathetic control in terms of salivary secretion?

A

Cervical ganglion

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15
Q

Which ANS stimulus dominates over regulation of salivary secretion?

A

Parasympathetic!

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16
Q

What are 2 unique features about the regulation of salivary secretion?

A
  1. Salivary is ONLY contolled by the ANS
  2. Both Para and sympathetic increase salivary secretion
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17
Q

Conditioning, food, nausea, smell all stimulate what?

A

Saliva secretion

HCO3 + enzyme secretions

Contraction of myoepithelial cells

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18
Q

Dehydration, fear, sleep all inhibit what?

A

They decrease saliva secretion

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19
Q

Describe the diagram for regulation of salivary secretion by the ANS

A
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20
Q

Pepsiongen + HCl (H+) do what?

A

Protein digestion + kill bacteria

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21
Q

Why is mucus important?

A

It protects the wall of the stomach from damage

Lubricant

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22
Q

What is intrinsic factor required for?

A

Absorption of Vitamin B12 in the ileum

(If no B12 –> anemia) It is important for RBC’s

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23
Q

There are two glands in the gastric mucosa: the oxyntic gland and the pyloric gland. What is the function of each gland?

A

Oxyntic gland: (body) –> secretes acid

pyloric gland: (antrum) –> synthesize + release gastrin

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24
Q

What secretes the “gastric juice”? Cells in the gastric mucosa

A
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25
Q

What determines the max secretion rate of HCl?

A

of parietal cells

26
Q

Why is the pH of the stomach so low?

A

It converts pepsinogen to pepsin (breaks down proteins)

27
Q

In gastric parietal cells, which enzyme catalyzes the reaction of CO2 + H20 —-> H2CO3 —-> H+ + HCO3-?

A

Carbonic Anhydrase

28
Q

Describe the reaction taking place in a gastric parietal cell to secrete HCl.

A
29
Q

A patient is vomiting, what is the composition of gastric juice coming up their esophagus?

A

Non-parietal: alkaline (Na+, Cl-, K+)

Parietal: Hyperosmotic (H+, K+, Cl-)

30
Q

Describe the diagram of agents that stimulate or inhibit gastric parietal cell secretion.

A
31
Q

The vagus nerve can stimulate HCl secretion in the stomach via 2 pathways, a direct and indirect pathway. How does the direct pathway work? What inhibits it?

A

Vagus N. –> ACh –> Parietal Calls –> HCl

Atropine

32
Q

How does the indirect pathway via the vagus nerve work?

A

Vagus N. –> GRP –> G cells –> Gastrin (into blood) –> Parietal cells –> HCl

33
Q

How is gastrin release regulated?

A

Via negative feedback. When gastrin release gets too high, gastrin itself will increase the release of somatostatin which inhibits gastrin release by G cells.

Also, secretin also inhibits gastrin release

34
Q

The drug cimetidine exerts its effect on _______. Why do people use it?

A

H2 receptors (Histamine)

It treats duodenal + gastric ulcers, and GERD

35
Q

The drug Omeprazole blocks which proton pump? Why?

A

H+ - K+ ATPase

It reduces overall H+ secretion to treat ulcers (best drug).

36
Q

What are the 3 phases of gastric HCl secretion?

A

Cephalic phase (30%)

Gastric phase (60%)

Intestinal phase (10%)

37
Q

Vagotomy abolishes which phase?

A

Cephalic phase

38
Q

Besides distension and amino acid peptides, what else can stimulate gastric HCl secretion in the gastric phase?

A

Coffee!!! (thats why its good for you)

39
Q

At what time do we secrete pepsinogen?

A

Only when we have a low gastric pH (around 2.0) because then it is acidic enough to convert pepsinogen to pepsin.

40
Q

What is the cause of pernicious anemia?

A

Parietal cells do not secrete enough Intrinsic factor, and Vitamin B12 is too low

41
Q

What are the main components that make up the gastric mucosa to protect the stomach from H+ and pepsin?

A

HCO3- and Mucus

42
Q

HCO3-, mucus, prostaglandins, mucosal blood flow, and gastrin growth factors ______ the gastric mucosa.

A

PROTECT

43
Q

Acid (H+), pepsin, NSAIDs (asprin), H. Pylori, alcohol, smoking, bile, and stress _______ the gastric mucosa.

A

DAMAGE

44
Q

What is Zollinger - Ellison Syndrome?

A

A tumor (usually in pancreas) that secretes a shit ton of gastrin.

High H+ secretion by parietal cells + trophic effect

Can cause steatorrhea (lipids in diarrhea)

45
Q

What do we measure to determine if someone has a gastrin secreting tumor?

A

Secretin

Becuase normally this would inhibit gastrin release, but in this tumor it actually increases gastrin release.

46
Q

What are the two main causes of peptic ulcer disease?

A
  1. H. Pylori
  2. NSAIDs
47
Q

What are the two types of peptic ulcer disease?

A
  1. Gastric ulcers –> gastric mucosal barrier damaged
  2. Duodenal ulcers –> Increased H+ secretion
48
Q

Why is H. Pylori bad?

A

It damages the gastric mucosa via the enzyme urease, which converts urea to ammonia and causes the local environment to be alkaline. NH4+ then damages epithelial cells.

49
Q

Can you name the 3 ulcer diseases and what their H+ and Gastrin levels look like?

A
50
Q

What is the main ingredient in pancreatic juice that neutralizes stomach acid?

A

HCO3-

51
Q

Instead of para and sympathetic effects both increasing like in the salivary glands, in the exocrine pancreas what are their roles?

A

Normal (sym inhibits)

52
Q

What is the sympathetic innervation for the exocrine pancreas?

A

celiac and superior mesenteric plexuses

53
Q

What is the parasympathetic innervation for the exocrine pancreas?

A

Vagus N.

54
Q

The exocrine pancreas secretes a ________ solution. The acinus secrete ________ and the ducts secrete ___________.

A

Isotonic

enzymes

aqueous solution containing HCO3-

55
Q

Which enzyme secreted by acinar cells of the pancreas has to be activated in the duodenum?

A

Proteases

56
Q

Describe the mechanisms of transport across a pancreatic ductal cell.

A
57
Q

In cystic fibrosis, the CFTR channel in the pancreas contributes to an overproduction of mucous. Why?

A

Mutation in CFTR = Cl- channel in the apical surface of duct cell

Pancreas fails first from loss of HCO3 secretion

58
Q

Like gastric secretion, pancreatic secretion also has 3 phases, with the same names! Tell me what each phase secretes and which one is most important!

A

cephalic –> enzymatic secretion

gastric –> enzymatic secretion

intestinal (80%) –> enzymatic + aqueous secretion

59
Q

In the pancreas, how is enzyme secretion regulated during the intestinal phase?

A

I cells –> CCK –> IP3, Ca2 –> enzymes

60
Q

In the pancreas, how is aqeous secretion regulated during the intestinal phase?

A

S cells –> Secretin –> cAMP –> Aqueous secretion (Na+ and HCO3-)

61
Q
A

GI Final (12 decks)

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