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Q3 Physio II Test 1 > Gastric Digestion (lec 3) > Flashcards

Gastric Digestion (lec 3) Flashcards

1
Q

Orad of stomach is?

A

top

orad means “near the mouth”

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2
Q

Receptive Relaxation is?

A

VIP induced Vagovagal reflex

distension of low esophagus relaxes LES and orad

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3
Q

Stomach Body Wall structure? (3 structures)

A

Gastric Pits: duct opening in epithelial-lined mucosa

Gastric Glands: empty into ducts

Epithelial Lining: produces alkaline mucous

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4
Q

Gastric Glands made of what cell types? (2)

A

Parietal: secrete HCl and IF

Chief: secrete pepsinogen

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5
Q

Antrum of stomach is?

A

distal end, pyloric part

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6
Q

Stomach Antrum made of?

A

pyloric glands

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7
Q

Pyloric glands made of what cell types?

A

G cells: secrete gastrin into circulation

Mucous neck cells: secrete alkaline mucous, HCO3- and pepsinogen

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8
Q

Components of gastric secretion and purpose? (4)

A

1) HCl: activates pepsin, digests protein, kills bacteria
2) IF: vit B12 absorption in ileum, indispensible!
3) Pepsinogen/Pepsin: digests proteins
4) Mucus: lubrication, acid protection

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9
Q

What 2 components of gastric juices initiate protein digestion?

A

HCl and pepsinogen

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10
Q

Process of HCl secretion? (slide 12)

A

Parietal Cell forms H+ and HCO3-

H+ out into lumen / K+ in from blood via ATPase (blocked by omeprazole),

Cl- (thru Cl- channel) follows H+ into lumen,
makes HCl

K+ channel immediately pumps K+ from cell into lumen

HCO3- into blood via Cl- exchange (alkaline tide)

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11
Q

HCl secretion controlled by?

A

Gastrin (ECL cells -> histamine -> parietal cells) (blocked by cimetidine)

PNS (ACh -> parietal cells) (Blocked by atropine)

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12
Q

Gastrin fxn? (3)

A

stim acid and pepsin secretion

stim growth of gastric and intestinal mucosa

Stim antral and intestinal motility

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13
Q

Gastrin released from?

In response to?

A

from G cells of antrum when stim by:

1) peptides/AA in stomach
2) distention of stomach
3) vagus

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14
Q

HCl release inhibited by? (5)

A 
somatostatin
prostaglandins
pH < 3
chyme in duodemum (CCK, GIP)
atropine
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15
Q

Gastrin stimulates parietal cells how?

A

thru enterochromaffin-like cells (ELC):

gastrin stims ELC to release histamine ->
Histamine stims H2-receptors on parietal cells
(inhibited by Ranitidine/cimetidine)

Gastrin ALSO stim production of more parietal cells

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16
Q

How does Somatostatin inhibit HCl release? (3)

A

pH < 3 stim D cells to release somatostatin

1) paracrine-type inhibition of gastrin release
2) direct inhibition of parietal cells
3) ↓ effects of Gastrin, ACh and histamine (the steps needed to stim H2 receptors)

17
Q

How does Cephalic Phase of digestion stim HCl secretion? (3)

A

(30% of total HCl)

1) Vagal PNS stim of parietal cells thru ACh
2) GRP (PNS) stim of G cells to release Gastrin
3) Circulating Gastrin stims parietal cells

18
Q

What senses/conditions stim vagus reflex for digestion? (4)

A

taste
smell
chewing
swallowing

19
Q

Pepsinogen is?

A

inactive proenz
HCl activates it, becomes pepsin
**only released when pH low enough to ∆ to pepsin

20
Q

Pepsinogen secretion regulated how: Cephalic Phase?

A

(most important pepsinogen regulation)

chief cells directly stim by vagus (ACh)

21
Q

Pepsinogen secretion regulated how: Gastric Phase?

A

1) low pH locally stim chief cells
2) Gastrin stim chief cells
3) Secretin stim chief cells

22
Q

Pepsin fxn?

A

cleaves proteins for digestion

23
Q

Pepsinogen secretion inhibited by?

A

Somatostatin

24
Q

Mucus secreted by? (2)

A

1) Mucous Neck cells

2) Surface epithelium

25
Q

Mucus made of?

A

mucins (glycoproteins/carbs)

high HCO3- levels

26
Q

Mucus release stim by? (3)

A

1) vagus (PNS)
2) distention
3) prostaglandins

27
Q

Gastric Mucosal Barrier (GMB) fxn?

A

protect gastric mucosa from acid, enz, physical damage

28
Q

Gastric mixing and emptying stim by? (3)

A

1) PNS (Ach)
2) distention
3) Gastrin and Motilin during MMC

29
Q

Process of Gastric Motility? (3)

A

1) orad relaxation to accept food (VIP vagal reflex)
2) mixing
3) propulsion of chyme into duodenum

30
Q

Gastric mixing and emptying inhibited by? (5)

A

1) SNS (NE)
2) Secretin, CCK, GIP

3) *H+
4) *products of fat and proteins in duodenum
5) *distention of duodenum

*nervous entergastric reflex (not hormonal)

31
Q

MMC is?

A

Migrating Myoelectrical Complexes:

contractions to clear stomach every 90 minutes

32
Q

How does Gastric Phase of digestion stim HCl secretion? (3)

A

(60% of HCl release)

1) AA/peptides in stomach stim G cells to release Gastrin
2) Distention stims release of ACh:

  • direct vagal stim of parietal cells
  • indirect stim of parietal cells by causing G cells to release Gastrin into circulation

3) Alcohol, caffeine and Ca2+

33
Q

GMB keeps acid out how? (4)

A

1) mucosal membrane impermeable to H+ (lumen side)
2) tight jxns b/w mucus cells
3) mucus coating is physical barrier
4) mucus HCO3- is chemical barrier

Q3 Physio II Test 1 (6 decks)

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