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unit 6: physiology > Salivation and Gastric Function (2) > Flashcards

Salivation and Gastric Function (2) Flashcards

1
Q

Gastrin:

  1. What secretes it
  2. in response to what
  3. effects
A
  1. secreted by antral mucosal cells-G cells
  2. in response to food, distension, vagus
  3. inc acid secretion of parietal cells
    - stimulates growth of gastric mucosa
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2
Q

Motilin:

  1. what secretes it
  2. when
  3. what are the effects
A
  1. secreted by mucosa of small intestine- M cells
  2. during fasting period
  3. promotes contractions in distal stomach and intestine to clear indigestible materials
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3
Q

Where is the digestion of carbs and lipids initiated?

A

in the mouth
amylase - carbs
lipase - lipids

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4
Q

Where is the digestion of proteins initiated?

A

stomach - pepsins

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5
Q

What type of secretions does the acinar of the parotid glands, submandibular, sublingual secrete?

A

parotid - serous rich in alpha-amylase

submandib/sublingual - mucous rich

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6
Q

What is the component of salivary secretion that converts starch to sugar at a pH of 7?

A

ptaylin

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7
Q

What is lingual lipase secreted by?

A

salivary glands on tongue

-breaks down triglycerides

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8
Q

What is sjorgren syndrome?

A

autoimmune disease - destroys salivary and lacrimal glands

  • xerostomia - dry mouth
  • dental carries, halitosis, difficulty speaking
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9
Q

What does aldosterone stimulate?

A

Na+ reabsorption, K+ secretion

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10
Q

What do the pits in the body of the stomach contain?

A
  1. mucous neck cells
  2. peptic of chief cells - pepsinogen, gastric lipase
  3. parietal cells - HCl and intrinsic factor
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11
Q

What is achlorhydia?

A

when gastric acid secretion is low

-destruction of parietal cells

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12
Q

What is deficient in pernicious anemia?

A

intrinsic factor

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13
Q

What type of glands does the antrum of the stomach have?

A

pyloric glands:
deeper pits
fewer peptic cells
no parietal cells

G cells - gastrin
D cells - somatostatin

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14
Q

When are pepsin most active?

A

below pH 3.5

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15
Q

How are pepsinogens activated to pepsins?

A

at pH of 5-3, pepsinogens are spontaneously cleaved of an N terminal activation peptide

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16
Q

What is a diffusion barrier in the stomach for H+ and pepsins?

A

mucus layer produced by surface cells

17
Q

What happens if H+ penetrates into the gastric epithelium?

A

damages mast cells and histamine is released

-inflammatory response

18
Q

What happens as a result of chronic NSAID usage?

A

erosive gastritis

-inhibit PG synthesis which normally mantains mucous barrier

19
Q

What is the main driving force for HCl secretion by parietal cells?

A

H+ K+ ATPase at the luminal membrane

H+ into lumen, k+ into parietal cell

20
Q

What other diffusion process occurs at the apical membrane of a parietal cell, besides the H+/K+ ATPase?

A

Cl- passively flows out into the lumen

21
Q

What two pumps occur at the basolateral membrane of a parietal cell?

A
  1. Na”/K+ ATPase (3 Na+ out, 2 K+ in)
  2. HCO3-/Cl exchanger
    (HCO3- into blood, Cl- into cell)
22
Q

What does the final secretion of a parietal cell contain?

A

water
HCl 150 mEq/L
KCl 15 mEq/L
small amount of NaCl

23
Q

What has a higher pH: gastric venous blood or arterial blood?

A

gastric venous blood

-alkaline tide

24
Q

What does prolonged vomiting cause?

A

dehydration, alkalosis, hypoalkemia

25
Q

Where is the vomiting center?

A

medulla

26
Q

What are the stimulators of acid secretion?

A
  1. histamine from ECL cells
  2. vagus - indirect and direct effects
  3. gastrin - directly on parietal cells, stimulates histamine release
  4. insulin - directly on parietal cells
  5. caffiene - inhibits phosphodiesterase
  6. stress
27
Q

What are the inhibitors of acid secretion?

A
  1. somatostatin
  2. GIP
  3. secretin
28
Q

Where is somatostatin released from and how does it react?

A

released from endocrine cells in gastric pits

  • acts in a paracrine manner on parietal and G cells
  • inhibits gastrin
29
Q

What is GIP released from and how does it react?

A

released from duodenum and jejunum

-acts directly on parietal cells

30
Q

What is secretin released from and how does it react?

A

released from duodenum and jejunum

acts on G cells to inhibit gastrin secretion

31
Q

What phase does most of the HCl regulation occur in?

A

gastric phase

32
Q

Describe the cephalic phase?

A
  • smell taste, condition reflexes
  • HCl secreted by direct stim of vagus
  • indirect stim of parietal cell by gastrin
33
Q

Describe the gastric phase?

A
  • distension of the stomach
  • presence of breakdown products
  • direct and indirect vagus affects and distention of antrum –> gastrin release
34
Q

Describe the intestinal phase?

A

mediated by products of digestion

HCl ingestion is inhibited when no longer needed for activation of pepsin

unit 6: physiology (13 decks)

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