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PHYSIO > GI2 > Flashcards

GI2 Flashcards

1
Q

What endocrine secretions control the stomach secretions?

A

Gastrin (also in intestines)- stimulates gastric glands

CCK- delays gastric energy

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2
Q

What paracrine/neural secretions control the stomach secretions?

A

somatostatin- inhibits acid and pepsinogen secretion and release of gastrin
histamine- stimulates acid secretion
Neural:
Vagus can release ACh and GRP

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3
Q

What do parietal cells release?

A

HCL and intrinsic factor

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4
Q

What do chief cells release?

A

Pepsinogens (stimulated by GRP), gastric lipase

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5
Q

What do endocrine cells release?

A

Somatostatin and gastrin

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6
Q

Intrinsic factor is the only indispensable secretion required for B12 absorption where?

A

duodenum

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7
Q

What does gastrin do and where is it released from?

A

endocrine cells in the stomach, and it stimulates gastric glands to secrete hydrochloric acid and pepsinogen

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8
Q

R proteins

A

protects vitamin B12 from degradation, it has a high affinity for B12 in the acidic environment and is cleaved by trypsin in the duodenum and intrinsic factor takes over.

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9
Q

Ghrelin does what?

A

a hormone released when fasting and stimulates the hypothalamus to stimulate hunger, it opposes the effects of peptide YY and leptin.

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10
Q

Somatostatin is released from what type of endocrine cells? and where are they found?

A

D cells- inhibit gastrin and HL released; found in stomach and pancreas

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11
Q

What do G cells release? and where are they found?

A

gastrin, they stimulate parietal cells; stomach

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12
Q

What do ECL cells secrete? and where are they found?

A

Histamine, which stimulates CHL secretion; found in stomach

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13
Q

Parietal cells releases HCL which causes an increase in what electrolytes?

A

Cl, H, K

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14
Q

What ENDOCRINE hormones regulate HCL production?

A
  1. gastrin- stimulates HCL and pepsinogen
  2. GIP- from stomach, stimulates gastrin and pepsinogen release
  3. secretin (from duodenum and works indirectly) - inhibits gastrin
  4. Peptide YY (indirectly)
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15
Q

What PARACRINE hormones regulate HCL production

A

Histamine and serotonin (vasoconstrictor actions in the intestines that are associated with peristalsis, 5HT useful as an antiemetic)

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16
Q

Neural control of HCL production?

A

Vagal AcH acts on D cells to release somatostatin, parietal cells (produces HCL), mast cells (serotonin increases peristalsis), and GRP (stimulates gastrin and pepsinogen release)

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17
Q

What hormones inhibit gastric acid secretion?

A

Secretin (acts on G cells)
Somatostatin (acts on parietal cells)
GIP from small intestines (acts on parietal cells to inhibit gastric secretion)
Peptide YY (indirect)
Prostaglandins (inhibit ECL cell histamine release, and G cells)

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18
Q

What stimulates HCL acid secretion?

A

parasympathetics
AcH
gastrin
histamine

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19
Q

What is pepsinogen secreted by and who stimulates its release?

A

CHEIF cells!

stimulated by vagus, gastrin, histamine, secretin, CCK

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20
Q

When one has H pylori, what disrupts the mucus/bicarb barrier?

A

mucinase

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21
Q

What are the three phases of gastric secretion?

A

Cephalic, Gastric, Intestinal

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22
Q

What is the Cephalic phase characterized by?

A

anticipation, chemo/mechano receptors on tongue and buccal canal, nasal mucosa
*vagal effects! = gastrin secretion, acid, enzymes

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23
Q

What is the gastric phase characterized by?

A

food in stomach, vagal effects (gastrin, acid, enzymes, pH changes)

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24
Q

What is the intestinal phase characterized by?

A

Inestional mucsa secretions (mucus, hormones, enzymes), secretions from the pancreas and liver, gallbladder to enter to duodenum. Highly acidic chyme enters the duodenum and the composition of the chyme is important, feedback to HCL secretion, decreases gastric emptying.

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25
Q

When chyme enters the stomach, what happens?

A

secretin is secured from the small intestine, stimulates the pancreas to release its alkaline juice, liver secretes bile, and decreases GI motility, also inhibits further gastrin secretion (which delays emptying and acid secretion)
we have an increase in bicarb in the small intestine which allow the pancreatic enzymes to work efficiently!

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26
Q

What hormone in the small intestine stimulate the crypt cells? and what do the crypt cells do?

A

Secretin; the crypt cells have CFTR which secrete Cl into the lumen of the gut. Na and H2O follow.

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27
Q

What are the major cell types of the small intestines?

A

Crypt cells, Paneth cells, Goblet cells, Endocrine cells, Brunners glands

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28
Q

What are paneth cells and where are they located?

A

Small intestines, they help with host defense, secreting zine and lysozymes that attack bacteria

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29
Q

What are goblet cells and where are they located?

A

small intestine, and secrete mucus

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30
Q

What are the endocrine cells of the small intestine for?

A

secreting:
1. Gastrin
2. CCK
3. Secretin
4. GIP
5. Motilin
6 Serotonin
7. VIP

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31
Q

What are Brunner’s glands and where are they located?

A

In the small intestines in the first part of the duodenum before the sphincter of Oddi, secretes thick mucus and proteases, stimulated by SECRETIN. inhibited by vagus.

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32
Q

Where is enterokinase formed?

A

Duodenum (small intestine)

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33
Q

Gastrin

A

Secreted from G cells in antrum of stomach and duodenum
Stimulated by stretch, peptides and AA, by vagus releasing the GRP
Simulates gastric acid secretion, increases gastric mixing, increases gastric motility

34
Q

Secretin

A

Secreted by small intestine: S cells of the duodenum
Simulated by acidic chyme
Increase pancreatic buffer secretion, INHIBITS GASTRIN, delays gastric emptying

35
Q

CCK

A

Secreted by small intestine: duodenum
Simulated by peptides, AA, fats
stimulates gallbadder to eject bile and pancreas to secrete alkaline fluid, decreases gastric motility, DELAYS GASTRIC emptying, inhibits gastrin

36
Q

GIP

A

Secreted by small intestine: duodenum and jejunum

Inhibits gastric secretion and gastric emptying

37
Q

Motilin

A

Secreted by small intestine (when fasting or when acid or fat is present)
STIMULATES PHASE III CONTRACTIONS OF THE MMC

38
Q

Peptide YY

A

Secreted by small intestine, at the end of the meal, decreases HCL and pancreatic enzymes

39
Q

Gastrin, secretin, and CCK are endocrine or exocrine?

A

endocrine

40
Q

What hormones are released by the stomach?

A

Gastrin, histamine, somatostatin, acetylcholine (vagus), GRP (vagus)

41
Q

What stimulates pancreatic enzyme release?

A

CCK! also, insulin, secretin, vagovagal reflexes.

42
Q

Where does activation of the pancreatic proteases occur?

A

Duodenum

43
Q

What cells in the pancreas secrete enzymes and buffers?

A
  1. acinar- on the outside, produce enzymes
  2. centroacinar- make a solution rich in bicarb- stimulated by secretin!!
    These empty into the extralobular ducts into the main ducts
    There is further secretion and reabsorption in the extra lobar but not the main duct!
    secretions from pancreas are both endocrine and exocrine
44
Q

Pancreas endocrine glands secrete what?

A

insulin
glucagon
somatostatin
*these can all affect gastric secretion and motility

45
Q

Pancreas exocrine glands secrete what?

A

enzymes and electrolytes

46
Q

Which cells in the pancreas produce secretions with lots of bicarb and what are they stimulated by?

A

Centroacinal cells, and secretin

47
Q

What types of food does the pancreas help breakdown?

A
  1. Oligosaccharides (pancreatic amylase)
    - breaks them into lactose, maltose, sucrose
  2. Proteases (trypsin, chemotrypsin, carboxypeptidase)
  3. Fats (pancreatic lipase)
48
Q

Proteases secreted by the pancreas are secreted as what?

A

zymogens

49
Q

trypsinogen is activated by what to trypsin where?

A

Trypsinongen activated to trypsin by enterokinase in the duodenum

50
Q

Trypsin activates what?

A

chemotrypsinogen —> chemotrypsin

Procarboxypeptidase—> carboxypeptidase

51
Q

Trypsin inhibitor is located primarily where?

A

In the pancreatic duct

52
Q

What are the two “-ases” secreted by the pancreas?

A

pancreatic lipase and pancreatic amylase
Pancreatic lipase and pre-colipase hydrolyze lipids, at the level of emulsified fats after the bile acids emulsify
pancreatic amylase- starch breakdown at the level of oligosaccharides

53
Q

When the chyme reaches the where do the secretions need to stop and how is this accomplished?

A

Ileum, SS, glucagon, pancreatic polypeptide, peptide YY

54
Q

What two electrolytes does the Ileum secrete?

A

H and Bicarb, carbonic anhydrase is in the enterocytes of the ileum and the secreted H acidifies the lumen so bicarbonate is also secreted as a buffer in exchange for Cl.
bicarb goes out into the lumen and Cl comes in!

55
Q

What electrolytes get secreted by the colon?

A

H, and HCO3 get secreted into the lumen,
*colon is sensitive to ALDOSTERONE and K can be excreted or conserved as needed
Goblet cells also secrete mucus (stimulated by contact, PSNS, and enteric nervous system)
*colon also produces carbonic anhydrase and bicarb gets secreted into lumen to buffer the acid prone chyme

56
Q

What is a characteristic of the small intestine that allows for avid absorption?

A

villous lining

57
Q

What enzymes does the stomach produce?

A

Pepsins and gastric lipase

58
Q

What enzymes does the exocrine pancreas produce?

A

trypsin, chemotrypsins, pancreatic lipase, pacreatic colipase, pancreatic amylase

59
Q

What do the brush border enzymes consist of?

A

lactase, sucrase, maltase, peptidases,

60
Q

What does trypsin do?

A

Relased by the pancreas, is activated by enterokinase, breaks proteins and polypeptides down to smaller peptide chains

61
Q

What does pancreatic lipase and pancreatic amylase do?

A

Pancreatic lipase breaks down fats to monoglycerides and free fatty acids
Pancreatic amylase breaks down oligosaccharides to lactose, maltose, sucrose (then brush border enzymes lactase, maltase, sucrase break them down)

62
Q

GLUT 5
SGLT1
GLUT2

A

Apical GLUT 5- FRUCTOSE from apical side to lumen
Apical SGLT 1- joining NA and GLUCOSE AND GALACTOSE can also join; apical side to lumen (dependent on NA concentration)
Basolateral GLUT2- fructose, glucose and galactose into the blood!
*these all work off the NA gradient
*Basolateral Na/K pump, keeps Na low inside the cell, pumps

63
Q

Are carbohydrates hydrophilic or hydrophobic?

A

Hydrophilic- they move easily through the membrane

64
Q

Steps of protein breakdown:

A

Stomach: HCL digests proteins; HCL stimulates secretion of pepsinogens (pepsins); pepsins break down proteins to peptones,
Pacnrease secretes zymogens into the duodenum through the pancreatic duct, trypsin inhibitor is located in the interlobular and main ducts; also sureties nucleases that break nuclei acids into purine bases
Small intestine: enterokinase is activated and then activates trypsin which activates the zymogens

65
Q

Sodium linked co-transporters can carry what?

A

neutral amino acids from the outside of the cell, into the cell for use

66
Q

Steps of lipid digestion:

A
  1. Lingul lipase cleaves TG to FA and DG
  2. Stomach has gastric lipase which cleaves TG to FA and DG
  3. Small Intestine: peptides and fats ion the duodenum triggers CCK release which causes gallbladder constriction, sphincter of Oddi relaxation to release pancreatic enzymes,
    Pancreatic enzymes: lipase turns TG to FA and MG
    Small intestine: cholesterol esterase breaks cholesterol esters to cholesterol and fatty acids, which can diffuse through the enterocytes
  4. Colipase is secreted from the pancrease and is activated in the duodenum by trypsin (then one lipase forms a complex with one collapse)
67
Q

Gastrocolic

A

mass movements in colon after mean

68
Q

Gastroileal

A

increased segmentation in ileum in response to gastric emptying

69
Q

What transports lipids to the brush border (unstirred water layer) to the enterocytes?

A

Micelles, amphipathic, then the fatty acids, phsospholipids, cholesterol, monoglycerides diffuse over.

70
Q

What happens after the lipids diffuse through the membranes?

A

enter to the SER, resterfied with FFA, into TG, PL and cholesterol esters, the chylomicrons then reenter the lymph lacteals

71
Q

Most bile absorption occurs where?

A

in the terminal ileum via secondary active transport with sodium

72
Q

Water absorption occurs primarily where?

A

Jejunum and ileum, colon reabsorps 0.5L; small intestines reabsorb the most at 8500mk/day

73
Q

Colonic movements

A

no vili, slow movement due to hausfrau, colonic salvage is final absorption of water and sodium. Fecal production begins in late colon. K and HCO3 are main components!

74
Q

Both lingual lipase and gastric lipase yield what?

A

free fatty acids and diglycerides

Different than pancreatic lipase which hydrolyzes TG to two FA and one monoglyceride

75
Q

Cephalic phase:

A

food in mouth initiates vagal release of Ach at parietal cell, stimulating acid secretion, vagal fibers also terminate on the ECL and G cells.

76
Q

Gastric phase

A

Stretch releases gastrin from G cells, goes in bloodstream and stimulates the proton pump of the parietal cell. Vagus also stimulates GRP and histamine

77
Q

Intestinal phase

A

Vagus acts directly on parietal cells, histamine acts on adjacent parietal cells

78
Q

Somatostatin

A

acts in a paracrine manner on the parietal cells as well on the G cells to inhibit gastrin

79
Q

What is released and activated by trypsin in the duodenum which helps to allow pancreatic lipase to access the lipids?

A

Colipase is released as precolipase and activated by trypsin, the collapse binds to the bile and allows the pancreatic lipase to access the lipids

80
Q

In the colon, what transporter reabsorbs Na?

A

Na/H exchanger. H is secreted into the lumen, CL also reabsorbed through the CL/HCO3 exchanger. thus H and HCO3 secreted in lumen.

81
Q

Gas is produced by what?

A

H2, N2, methane.

PHYSIO (7 decks)

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