Exam 5 GI Flashcards
Gastrin
location?
function?
stomach (G cells)
gastric acid secretion & gastric motility & stimulates pancreas to release digestive enzymes
CCK
location?
function?
small intestine duodenal cells
secretion of pancreatic digestive enzymes, secretion of bile, satiety, and control gastric motility (inhibits gastric activity)
Secretin
location?
function?
small intestine epithelium
secretion of bicarb and water & helps inhibit gastric activity
Ghrelin
location?
function?
stomach (gastric epithelial cells)
appetite stimulation and promotes fat storage
leptin
location?
function?
adipocytes
decrease appetite, satiety
motilin
location?
function?
small intestine epitheial cells
controls smooth m contraction/ responsible for migrating motor complex
glucagon
location?
function?
pancreas
increased blood glucose levels
insulin
location?
function?
pancreas
control blood glucose levels (decreases) & stimulates storage of excess sugar & also modulates fat storage for hibernators
aldosterone
location?
function?
adrenal glands
sodium and water reabsorption
proenzymes/zymogens
inactive enzymes
pepsinogen
location?
function?
chief cells in stomach
protein breakdown
trypsinogen
location?
function?
pancreatic exocrine cells
activated by enterokinase to activate chymotrypsinogen –> chymotrypsin & protein digestion
chymotrypsinogen
location?
function?
pancreatic exocrine cells
activated by trypsin for protein digestion
lipase
location?
function?
pancreatic exocrine cells
hydrolyzes triglycerides –> free fatty acids + glycerol
requires bile acids
amylase
location?
function?
pancreatic exocrine cells
hydrolyzes starch –> glucose
adenylyl cyclase
location?
function?
enterocytes
activates CFTR which increases Cl- in the lumen
brush border hydrolyases
enzymes that break down carbohydrates into simple sugars
lysosyme
location?
function?
glandular epithelium of abomasum
breaks down bacterial cell walls
cellulase
location?
function?
microbes in GI tract
break down cellulose –> glucose
submucosal plexus
senses environment within the lumen, regulates GI blood flow and controls epithelial cell function
sensory normals (respond to chemical, thermal, osmotic, mech. stimuli)
myenteric plexus
controls digestive tract motility
motor neurons
what nerve is important for feeding behavior
vagus n.
what prevents the esophagus from trauma
stratified squamous epithelium
gastroesophageal reflux disease (GERD)
improper closing of lower sphincter
megaesophagus
dilation/loss of motility of esophagus
surfous mucous/mucous neck cells
mucus to protect epithelium
parietal cells
HCl
chief cells
pepsinogen
endocrine cells of the stomach
gastrin
gastic motility in upper stomach vs lower
upper = low frequency of sustained contractions to maintain basal pressure and gastric emptying
lower = strong peristaltic waves of contraction (gastric grinding)
four phases of the migrating motor complex
quiescence
peristaltic contractions
rapid contractions
short transition period
what is the enterogastric reflex
slowing down of the small intestine
SI releases CCK/secretin to suppress gastric activity
intrinsic barrier vs extrinsic barrier
intrinsic = epithelial cells line digestive tube & tight junctions & cell turnover
extrinsic = maintains epithelial cells, mucus, bicarb. etc.
disruptions of the barriers
stress
ischemic reperfusion injury
infectious agents
what controls vomitting
vomination centers in the medulla with chemoreceptor trigger zones
visceral afferents from GI tract (e.g. distension)
visercal afferents from outside GI tract (e.g. bile)
afferents from extramedullary centers in brain (e.g. odors, fear)
mechanisms that protect pancreas from autodigestion
- proenzymes/zymogens
- bicarb/water
portal triad
hepatic a.
portal v.
bile duct
intrahepatic biliary system vs extrahepatic
intra has canaliculi and extra has series of channels/ducts (e.g. common bile duct)
metabolic fate of heme and formation of bilirubin
heme eliminated by conversion to bilirubin which is conjugated and secreted into SI where it is metabolized by gut bacteria and eliminated
gives feces brown color
villi components vs crypt
villi has enterocytes and goblet cells
crypts have stem cells and secretory epitheial cells
2 processes of microbial flora
digestion/metabolism of cellulose and excess starch
synthesis of vitamin K, B and VFAs
cranial fermenters vs caudal fermenters
cranial: starch/carbs fermented into VFAs in stomach, protein is utilized
caudal: do not utilize protein, directly utilize hexose
importance of ruminal bacteria
major source of protein, synthesize proteins and vitamins, metabolize VFAs, and enzymes to digest cellulose
VFAs
major fuel source for energy
acetic acid, propionic acid, butyric acid
frothy bloat vs free gas bloat
frothy due to diet
free gas due to not able to eructate
