Gastrointestinal - Physiology

Question 1

gastrin source

Answer 1

G cells - antrum of stomach

Question 2

gastrin actions

Answer 2

increase gastric H+ secretion
increase growth of gastric mucosa
increase gastric motility

Question 3

gastrin regulation

Answer 3

increase by stomach distention, alkalinization, amino acids, peptides, vagal stim
decrease by stomach pH < 1.5

Question 4

gastrin fun facts

Answer 4

increased in ZE syndrome
increased by chronic PPI use
phenylalanine & tryptophan potent stimulators

Question 5

cholecystokinin source

Answer 5

I cells - duodenum, jejunum

Question 6

cholecystokinin actions

Answer 6

increase pancreatic secretion
increase gallbladder contraction
increase sphincter of Oddi relaxation
decrease gastric emptying

Question 7

cholecystokinin regulation

Answer 7

increase by fatty acids, amino acids

Question 8

secretin source

Answer 8

S cells - duodenum

Question 9

secretin actions

Answer 9

increase pancreatic HCO3- secretion
increase bile secretion
decrease gastric acid secretion

Question 10

secretin regulation

Answer 10

increase by acid, fatty acids in lumen & duodenum

Question 11

somatostatin source

Answer 11

D cells - pancreatic islets, GI mucosa

Question 12

somatostatin actions

Answer 12

decrease gastric acid, pepsinogen secretion
decrease pancreatic, s.i. fluid secretion
decrease gallbladder contraction
decrease insulin, glucagon release

Question 13

somatostatin regulation

Answer 13

increase by acid

decrease by vagal stimulation

Question 14

somatostatin fun facts

Answer 14

inhibitory hormone
antigrowth hormone
“somatostatin stops stuff”

Question 15

glucose-dependent insulinotropic peptide

gastric inhibitory peptide (GIP) source

Answer 15

K cells - duodenum, jejunum

Question 16

GIP action

Answer 16

exocrine: decrease gastric H+ secretion
endocrine: increase insulin release

Question 17

GIP regulation

Answer 17

increase by fatty acids, amino acids, oral glucose

Question 18

vasoactive intestinal polypeptide (VIP) source

Answer 18

parasympathetic ganglia in sphincters, gallbladder, s.i.

Question 19

VIP action

Answer 19

increase intestinal water, electrolyte secretion

increase relaxation of intestinal smooth m. & sphincters

Question 20

VIP regulation

Answer 20

increase by distention, vagal stim

decrease by adrenergic input

Question 21

VIPoma

Answer 21

non-alpha, non-beta islet cell pancreatic tumor that secretes VIP
WDHA syndrome
Watery Diarrhea
Hypokalemia
Achlorhydria

Question 22

Nitric oxide action

Answer 22

increase smooth m. relaxation, including LES

Question 23

motilin source

Answer 23

s.i.

Question 24

motilin action

Answer 24

produces migrating motor complexes (MMCs)

Question 25

motilin regulation

Answer 25

increase in fasting state

Question 26

intrinsic factor source

Answer 26

parietal cells - stomach

Question 27

intrinsic factor actions

Answer 27

Vit B12 binding protein - uptake in terminal ileum

Question 28

intrinsic factor fun facts

Answer 28

autoimmune destruction of parietal cells leads to chronic gastritis and pernicious anemia

Question 29

gastric acid source

Answer 29

parietal cells - stomach

Question 30

gastric acid action

Answer 30

decrease stomach pH

Question 31

gastric acid regulation

Answer 31

increase by histamine, ACh, gastrin | decrease by somatostatin, GIP, prostaglandin, secretin

Question 32

gastrinoma

Answer 32

gastrin-secreting tumor that causes continuous high levels of acid secretion and ulcers

Question 33

pepsin source

Answer 33

chief cells - stomach

Question 34

pepsin action

Answer 34

protein digestion

Question 35

pepsin regulation

Answer 35

increase by vagal stimulation, local acid

Question 36

how pepsin becomes pepsin

Answer 36

inactive pepsinogen becomes pepsin by H+

Question 37

HCO3- source

Answer 37

mucosal cells - stomach, duodenum, salivary glands, pancreas | Brunner's glands - duodenum

Question 38

HCO3- action

Answer 38

neutralizes acid

Question 39

HCO3- regulation

Answer 39

increase by pancreatic and biliary secretion with secretin

Question 40

saliva fun facts

Answer 40

amylase - digests starch HCO3- neut bac acids mucins - lubricate food normally hypotonic, isotonic w/ higher flow rates

Question 41

Brunner's glands

Answer 41

located in duodenal submucosa secrete alkaline mucus hypertrophy seen in PUD

Question 42

pancreatic secretion: alpha-amylase | function

Answer 42

starch digestion

Question 43

pancreatic secretion: lipase, phospholipase A, colipase | function

Answer 43

fat digestion

Question 44

pancreatic secretion: proteases | function

Answer 44

protein digestion

Question 45

pancreatic secretion: proteases | roll call

Answer 45

``` trypsin chymotrypsin elastase carboxypeptidases proenzymes = zymogens ```

Question 46

pancreatic secretion: trypsinogen | 411

Answer 46

converted to active trypsin by enterokinase/enteropeptidase secreted from duodenal mucosa activates other proenzymes and positive feedback

Question 47

carbohydrate digestion: salivary amylase

Answer 47

hydrolyzes alpha-1,4 linkages, makes disaccharides (maltose, alpha-limit dextrins)

Question 48

carbohydrate digestion: pancreatic amylase

Answer 48

highest concentration in duodenal lumen | hydrolyzes starch to oligosaccharides, disaccharides

Question 49

carbohydrate digestion: oligosaccharide hydrolases

Answer 49

brush border of intestine, rate-limiting step in carbohydrate digestion, produce monosaccharides from oligo- and disaccharides

Question 50

carbohydrate absorption

Answer 50

only monosaccharides absorbed by enterocytes glucose galactose fructose

Question 51

glucose, galactose uptake

Answer 51

SGLT1 - Na+ dependent | to blood by GLUT-2

Question 52

fructose uptake

Answer 52

facilitated diffusion by GLUT-5 | to blood by GLUT-2

Question 53

iron absorption

Answer 53

Fe 2+ in duodenum

Question 54

folate absorption

Answer 54

jejunum

Question 55

B12 absorption

Answer 55

terminal ileum along with bile acids | requires intrinsic factor

Question 56

Peyer's patches

Answer 56

unencapsulated lymphoid tissue lamina propria, submucosa of ileum contain M cells - take up antigen IgA

Question 57

bile contents

Answer 57

bile salts - conjugated bile acids to glycine, taurine so water soluble phospholipids cholesterol bilirubin water ions cholesterol 7alpha-hydroxylase catalyzes rate-limiting step

Question 58

bile functions

Answer 58

digestion, absorption lipids, DAEK cholesterol excretion antimicrobial activity - membrane disruption

Question 59

bilirubin definition

Answer 59

heme metabolism product | removed from blood by liver, conjugated with glucuronate, excreted in bile

Question 60

direct bilirubin

Answer 60

conjugated with glucuronic acid; water soluble | liver

Question 61

indirect bilirubin

Answer 61

unconjugated; water insoluble | macrophages