Lecture 19 -- review questions Flashcards
what are the 4 regions of the stomach?
cardia
fundus
body
pyloric part
what areas form the pyloric part of the stomach?
pylorus
pyloric canal
pyloric sphincter
antrum
how many layers of muscularis externa does the stomach have?
3 layers
what is the purpose of stomach rugae?
wrinkles (mucosal folds) that allow gastric expansion
where is the pyloric sphincter?
pyloric part of stomach
connects the stomach to the duodenum
what is the primary function of the pyloric sphincter?
regulates passage of chyme into duodenum
what 3 mechanisms protect the stomach from the harsh acidic and enzymatic environment?
1) mucous-bicarbonate barrier
2) epithelial tight junctions
3) damaged epithelial cell replacement (stem cells)
what its he pH of the stomach?
1.5
how often do epithelial cells regenerate (are renewed)?
3-6 days
the stomach’s epithelial cells have a mucous coat rich in which ion?
where is that ion coming from? (ie which cells produce it?)
bicarbonate ion
mucous neck cells
why can this ion help protect from acid that flow close to the stomach’s epithelial cells?
combines with H+ from acid to form H2O and CO2
does the stomach have any secretion coming from accessory glands?
no – stomach doesn’t have any secretions coming from accessory glands –> only from stomach glands
why are the stomach’s epithelial cells very close together, minimizing the space b/n them?
how is this achieved? (think about how the cells are joined)
packed close together to make sure no gastric juice seeps b/n them
what is the name of the gastric fluid secreted by the glands in the stomach: rich in water, acid, and pepsin called?
gastric juice
in the gastric glands, what do mucous cells secret?
mucus and bicarbonate
in the gastric glands, what do parietal cells secrete?
HCl (gastric acid)
intrinsic factor
in the gastric glands, what do chief cells secrete?
pepsin(ogen)
gastric lipase
in the gastric glands, what do G cells secrete?
gastrin
in the gastric glands, what do enteroendocrine cells secrete?
hormones – ghrelin, somatostatin, gastrin, serotonin
in the gastric glands, what do enterochromaffin cells secrete?
histamine
what is the intrinsic factor? where is it produced?
glycoprotein that aids in vitamin B12 absorption by small intestine
produced by parietal cells in stomach
what converts pepsinogen to active pepsin?
activated by HCl
the digestion of proteins begins in the stomach; which enzyme secreted in the gastric glands digests proteins?
pepsin
what is gastrin? what is its function in the stomach?
a hormone secreted by G cells
promotes parietal cells to secrete HCl
what is the name of the pump that plays an essential role in gastric acid production?
which 2 ions does it exchange?
H+/K+ ATPase
pumps K+ from stomach lumen into cytosol of parietal cell
pumps H+ from parietal cell to stomach lumen
what is the name of the acid of the stomach?
hydrochloric acid
where is the H+ used by the proton pump coming from?
carbonic acid (H2CO3) breakdown from inside the parietal cell
what cells produce acid in the stomach?
parietal cells
why do parietal cells transport the H+ and Cl- into the gastric lumen separately?
can’t create HCl directly in cytoplasm –> would destroy the cell
what stimulates stomach acid production? (indicate the 3 factors: neural, paracrine, and hormonal)
NAM PHH HGC
- new Amsterdam must play honey hockey house goose chase
neural:
- parasympathetic nerve fibers of both short and long reflex pathways
- ACh, M3
paracrine:
- histamine, H2
hormonal:
- gastrin, CCK2
which 2 factors stimulate the release of gastrin? by which cells?
peptides and increased pH
hormone-G cells (in duodenum and pyloric antrum)
what is called chyme?
acidic, soupy/pasty mixture of semi digested food
what are the names of the 3 phases of gastric acid secretion?
cephalic
gastric
intestinal
what stimulates gastric acid secretion during the cephalic phase?
thought, sight, smell, taste of food
which autonomic NS subdivision mediates the cephalic phase effects?
which enteric plexus is involved in this response?
parasympathetic NS
vagus nerve
submucosal/meissner’s plexus
what stimulates gastric acid secretion during the gastric phase?
food enters stomach and stretches stomach (distension) –> detected stretch receptors
gastrin is secreted
in which 2 phases does gastrin play a role in gastric acid secretion?
gastric
intestinal
what stimulates gastric acid secretion during the intestinal phase?
chyme arrives at duodenum –> duodenum is distended (stretched) –> detected by stretch receptors
gastrin is secreted
in which gastric acid secretion phase does the enterogastric reflex occur?
intestine
what is the name of the nervous reflex whereby stretching of the wall of the duodenum results in inhibition of gastric motility (including peristalsis) and reduced stomach emptying rate?
enterogastric reflex
which hormones are released during the intestinal phase by the duodenum and act on the stomach to inhibit gastric secretion and motility?
secretin
GIP (gastric inhibitory peptide)
CCK (cholecystokinin)
which factor stimulates the secretion of secretin by intestinal cells?
low pH
(chyme is very acidic –> duodenum doesn’t want to be that acidic)
what does GIP stand for?
gastric inhibitory peptide
what does CCK stand for?
cholecystokinin
where are CCK and secretin produced?
small intestine
what are the structural and functional units of the liver?
what is their shape in cross-section?
liver lobules
haxagonal shape
what are hepatocytes?
where are they found?
liver cells all throughout the liver
where is the portal triad found in the cross-section of a liver lobule?
spread out surrounding the central vein in the middle
what 3 structures make up a portal triad?
bile duct
hepatic artery
portal vein
where can you find Cholangiocytes?
epithelial cells in the bile duct
where can you find Kupffer cells? what are they?
line the endothelial sinusoids of the liver
macrophages
where can you find Stellate cells?
name 2 functions of these cells
located b/n endothelial sinusoids and hepatocytes of liver
major storage site for Vitamin A
activate fibrogenesis (scar creation) upon liver damage
which cells produce bile?
hepatocytes
after the production of bile, where is this bile secreted?
bile canaliculi (channels)
which “tube” connects the bile canaliculi w/ the bile (or biliary duct)?
canal of Hearing or Ductule
which hormone stimulates the cholangiocytes to secrete bicarbonate and water into the bile at the bile duct?
secretin –> stimulates cholangiocytes to stimulate bicarbonate and water into the bile at the bile duct
which 2 ducts form the common bile duct?
common hepatic duct
cystic duct
what is the ampulla of Vater or (hepatopancreatic ampulla)?
spot where the pancreatic and bile ducts release their secretions into the intestines
what sphincter controls the secretion of pancreatic juice and bile into the duodenum?
Sphincter of Oddi (hepatopancreatic sphincter) –> muscular valve
what does CCK produce in the gallbladder: contraction or relaxation?
does it help or oppose the stored bile’s secretion into the cystic duct?
contracts gallbladder
helps move bile from gallbladder into cystic duct to reach the small intestine
what does CCK produce in the Sphincter of Oddi: contraction or relaxation?
does it promote or prevent the secretion of bile and pancreatic juice into the duodenum?
relaxation
promotes bile and pancreatic juice to enter the duodenum
what is pancreatic juice?
bicarbonate-rich fluid containing enzymes that digests all categories of foods
carried to the duodenum via the pancreatic duct
in which organ of the alimentary canal is this pancreatic juice poured?
duodenum
pancreatic duct –> ampulla of Vater (hepatopancreatic ampulla)
which 2 types of cells form part of the exocrine pancreas?
acinar cells
duct cells
where are the acinar cells located (organ)?
acinar cells are found in acini (cluster units) of exocrine pancreas
what do acinar cells secrete?
which hormone stimulates this secretion?
enzyme-rich component of pancreatic juice
CCK stimulates acinar cells to secrete enzyme-rich component of pancreatic juice
which 2 ducts form the common hepatic duct?
left and right hepatic duct
what is the name of the granules found in the acinar cells?
what do they contain?
zymogen granules
contain inactive enzymes (proenzymes or zymogens)
what do pancreatic duct cells secrete?
which hormone stimulates this secretion?
watery secretion (rich in bicarbonate ions) of pancreatic juice
secretin stimulates pancreatic duct cells to secrete this watery secretin (rich in bicarbonate ions) of pancreatic juice
what are the Islets of Langerhans, and what do they produce?
make up the endocrine portion of the pancreas
produce insulin and glucagon
what are zymogen forms of enzymes?
trypsinogen –> ___
chymotrypsinogen –> ___
procarboxypeptidase –> ___
inactive digestive enzymes that get converted to active form after secretion
trypsinogen –> trypsin
chymotrypsinogen –> chymotrypsin
procarboxypeptidase –> carboxypeptidase
trypsin catalyzes production of more trypsin and activates the other pancreatic zymogen
what are 3 zymogens secreted by the pancreas for protein digestion?
what is the name of the corresponding active enzyme?
trypsinogen –> trypsin
chymotrypsinogen –> chymotrypsin
procarboxypeptidase –> carboxypeptidase
trypsin catalyzes production of more trypsin and activates the other pancreatic zymogen
