GI

Question 1

what cells make gastrin?

Answer 1

G cells

antrum of stomach, duodenum

Question 2

gastrin function?

Answer 2

increase gastric acid secretion
increase gastric mucosal growth
increase gastric motility

Question 3

regulation of gastrin secretion?

Answer 3

stimulated by: distention, alkaline, AAs, peptide, VAGUS
inhibited by: pH < 1.5

** increased in chronic atrophic gastritis, ZES, chronic PPIs

Question 4

what cells make somatostatin?

Answer 4

D cells

pancreatic islets, GI mucosa

Question 5

somatostatin function?

Answer 5

decrease secretion of: gastric acid, pepsinogen, pancreatic fluid, insulin/glucagon
decrease GB contraction

Question 6

regulation of somatostatin?

Answer 6

stimulated by acid

inhibited by VAGUS

Question 7

what cells make CCK?

Answer 7

I cells

duodenum, jejunum

Question 8

CCK function?

Answer 8

stimulate: pancreatic secretion, GB contraction, sphincter of Oddi relaxation
inhibit: gastric emptying

Question 9

CCK regulation?

Answer 9

stimulated by FAs, AAs

** acts on neural muscarinic pathways –> pancreatic secretion

Question 10

what cells make secretin?

Answer 10

S cells

duodenum

Question 11

secretin functions?

Answer 11

stimulates pancreatic HCO3 secretion, bile secretion

inhibits gastric acid secretion

Question 12

secretin regulation?

Answer 12

stimulated by acid, FAs in duodenal lumen

Question 13

what cells make GIP?

Answer 13

K cells

duodenum, jejunum

Question 14

GIP function?

Answer 14

exocrine: decrease gastric acid secretion
endocrine: stimulate insulin release

** oral glucose load more potent than IV glucose in terms of insulin release b/c of GIP response to oral glucose

Question 15

regulation of GIP?

Answer 15

stimulated by FAs, AAs, oral glucose

Question 16

what makes motilin?

Answer 16

SI

Question 17

what does motilin do?

Answer 17

produces migrating motor complexes

Question 18

motilin regulation?

Answer 18

increased in fasting state

** receptor agonists (e.g. erythromycin) used to stimulate intestinal peristalsis

Question 19

what makes VIP?

Answer 19

parasympathetic ganglia: sphincters, GB, SI

Question 20

VIP function?

Answer 20

increased intestinal water and electrolyte secretion

increased relaxation of intestinal smooth mm and sphincters

Question 21

VIP regulation?

Answer 21

stimulated by distention, VAGUS
inhibited by ADRENERGIC input

** VIPoma: copious watery diarrhea, hypokalemia, achlorhydria

Question 22

what substance is implicated in LES tone of achalasia?

Answer 22

NO (loss of it)

Question 23

what makes intrinsic factor? what does it do?

Answer 23

parietal cells, stomach

B12 blah blah blah

Question 24

what makes gastric acid?

Answer 24

parietal cells, stomach

Question 25

regulation of gastric acid?

Answer 25

stimulated by gastrin, histamine, ACh (vagus) | inhibited by SST, GIP, PGs, secretin

Question 26

what makes pepsin?

Answer 26

chief cells, stomach

Question 27

regulation of pepsin?

Answer 27

stimulated by VAGUS, local acid ** pepsinogen --> pepsin in presence of H+

Question 28

what makes HCO3 in GI tract?

Answer 28

mucosal cells and Brunner glands (duodenum)

Question 29

regulation of HCO3 secretion?

Answer 29

stimulated by pancreatic and biliary secretion with secretin

Question 30

what are enterochromaffin-like cells?

Answer 30

stimulated by gastrin --> make histamine --> stimulates parietal cell HCl release ** primary mechanism of gastrin --> HCl stimulation (greater contribution than direct stimulation of parietal cells)

Question 31

intracellular pathway for vagal stimulation of parietal cells?

Answer 31

ACh --> M3 receptor --> Gq --> IP3/Ca --> HCl release via H/K ATPase

Question 32

intracellular pathway for (direct) gastrin stimulation of parietal cells?

Answer 32

binds CCKb receptor --> Gq --> IP3/Ca --> HCl release

Question 33

intracellular pathway for histamine stimulation of parietal cells?

Answer 33

binds H2 receptor --> Gs --> cAMP --> HCl release

Question 34

intracellular pathway for PG/SST inhibition of parietal cells?

Answer 34

bind receptor --> Gi --> decreased cAMP --> decreased HCl release

Question 35

what converts trypsinogen to trypsin?

Answer 35

enterokinase/enteropeptidase | enzyme on brush-border (duodenum and jejunum)

Question 36

carb absorption in gut?

Answer 36

only monosaccharides absorbed glu and gal --> SGLT1 (Na dependent) --> GLUT2 --> blood fru --> GLUT5 (facilitated diffusion) --> GLUT2 --> blood

Question 37

vit/minerals absorbed in SI?

Answer 37

iron (Fe 2+) - duodenum folate B12 - TI, absorbed with bile salts, needs IF

Question 38

what are M cells?

Answer 38

in Peyer patches, present antigen to immune cells

Question 39

where are Peyer patches?

Answer 39

ileum - lamina propria and submucosa

Question 40

where do plasma cells of Peyer patches live?

Answer 40

lamina propria

Question 41

what is in bile?

Answer 41

``` bile salt = bile acids + gly/taurine phospholipids cholesterol bilirubin water ions ```

Question 42

what enzyme catalyzes rate limiting step of bile synthesis?

Answer 42

cholesterol 7 alpha hydroxylase

Question 43

functions of bile?

Answer 43

lipid/fat sol vitamin digestion/absorption cholesterol excretion antimicrobial activity

Question 44

first step of heme metabolism?

Answer 44

heme oxygenase converts to biliverdin

Question 45

what does biliverdin become?

Answer 45

unconjugated bili

Question 46

is unconjugated bili water soluble?

Answer 46

NO!

Question 47

what enzyme makes conjugated bili?

Answer 47

UDP glucuronosyl transferase - adds glucuronic acid

Question 48

what converts conjugated bili to urobilinogen?

Answer 48

gut bacteria

Question 49

what is stercobilin?

Answer 49

form in which bili is excreted in stool - gives brown color

Question 50

what is urobilin?

Answer 50

form in which bili is excreted in urine - gives yellow color