GI Secretions Flashcards
what secretion is in saliva
HCO3- K+ hypotonic α amylase lingual lipase
what increase salivary secretion
parasympathetic & sympathetic
what decrease salivary secretion
sleep, dehydration, atropine
what secretion in gastric secretion
HCl
mucin
pepsinogen
intrinsic factor
what increase secretion of HCl
gastrin
Ach
histaine
what increase secretion of pepsinogen
PNS
what decrease gastric secretion
H+ in stomach chyme in duodenum somatostatin atropine cimetidine omeprazole (prilosec)
what are the three major salivary glands
parotid
submandibular
sublingual
what does parotid gland secrete
secretes salt, water and enzymes that moisten food to enhance taste and digestion, provide some antibacterial action, and keep a more alkaline pH to protect teeth and mouth from gastric and food acids
what do submandibular and sublingual glands secrete
mostly mucus
what kinds of cells in parotid gland
serous cells
what do serous cells secrete
watery fluid with ions and enzymes, not mucousy
what kinds of cells in submandibular and sublingual glands
mixed mucous
serous cells
what do mucous cells secrete
mucin glycoprotein
what is xerostomia
deficient salivation
pts with xerostomia have greater risk for
dental cavities
describe serous acinar cells
zymogen granules that contain amylase
describe mucus acinar cells
secrete glycoprotein mucins
describe ductal cells
alter electrolyte concentrations in saliva
describe myoepithelial cells
eject saliva into mouth when stimulated by neuronal input
what is the functional unit of the salivary gland
salivon
the salivon consists of
acinus, the intercalated duct, the striated duct, and the excretory (collecting duct).
what is function of kallikrein
enzyme that acts on kininogen to release bradykinin – vasodilator which accounts for high salivary blood flow during increased salivary activity
draw out salivon
pg 9
what cells make initial saliva
acinar cells
what cells modify initial saliva
ductal cells
describe the fluid produced by acicnar cells that makes initial saliva
isotonic fluid w/ same electrolyte composition as plasma
striated duct epithelium is impermeable to
water
striated duct epithelium transports
salts
describe absorption and secretion of striated duct
abosrbs sodium and Cl-
secretes K+ and HCO3-
the striated duct epithelium does what to final secretion
makes it hypotonic but alkaline
saliva is always _____ to plasma
hypotonic
describe flow rates and what they do regarding saliva and ductal cells
low flow rate: the ductal cell has time to exchange ions. the result is that the saliva is much different from plasma, it has low concentrations of Na+ and Cl- and high concentation of K+
high flow rate: the ductal cell has less time to exhange ions. result is that saliva is not as much different from plasma.
kallikrein acts on
kininogen
kininogen releases what when akllikrein acts on it
lysyl-bradykinin
what does lysyl-bradykinin do
causes dilation of blood vessels supplying salivary glands
what does vasoactive intestinal peptide do
increases blood flow to salivary glandq
what does VIP stand for
vasoactive intestinal peptide
draw out the salivary ductal cell and the ion exchange in it
pg 11
blood flow in salivary glands is controlled by what system
PNS
draw out the PNS and SNS regulation of saliva
pg 14
what are the four major components of gastric juice
HCl
pepsinogen
intrinsic factor
mucus
what is function of HCl
acidic
initiates process of digestion
what is function of pepsinogen
initiates process of protein digestion
what is function of intrinsic factor
needed for absorption of vitamin B12
what part of stomach secretes HCl, intrinsic factor, and pepsinogen
body and fundus
what part of stomach secrete gastrin & somatostatin
antrum
all regions of stomach secrete
mucus
oxyntic also means
acid secreting
describe oxynitic gland of stomach
in body
empties secretory products, containsmucus cells, parietal cells, chief cells
what do mucous neck cells secrete
clear mucus
what do parietal cells secrete
HCl
intrinsic factor
what do chief cells secrete
pepsinogen
what kind of glands are in antrum of stomach
pyloric glands
what kinds of cells in pyloric glands
G cell
mucous cell
what do g cells secrete
gastrin
what do mucous neck cells in antrum secrete
mucus
HCO3-
pepsinogen
parietal cells are also called
oxyntic cells
chief cells are also aclled
peptic cells
the reason we need such a low pH in stomach is for
pepsinogen to become active → pepsin, to begin protein digestion
how do hydrogen ions enter stomach
H K ATPase pump
what cell are protons secreted from
apical membrane of parietal cells
what drug inhibits H, K ATPase
omeprazole
omeprazole is used in treatment of
ulcers, reduces H+ secretion
overal, what is the net secretion and abosrption of parietal cell
net secretion HCl and net absorption HCO3-
draw out the secretion and absorption of parietal cell
pg 23
what three subtances stimulate H+ secretion by parietal cells
ACh
histamine
gastrin
sympathetic acts mainly on what salivary glands
sublingual
three ways to stimulate acid secretion
gastrin
Ach
Histamine (they all potentiate each other)
what does potentiate mean
enhances the response of the other stimulus
how much secretions are produced each day
9L/day
parotid gland is mainly what cells
serous
what side of ductal cell is the sodium potassium exchanger
basolateral (side of blood)
why do you need bicarbonate in saliva
enzymes work at more alkaline pH
where is Ach released from
vagus nerves
ACh binds to what receptors
M3
second messengers for ACh are
IP3/Ca2+
what blocks muscarinic receptors on parietal cells
atropine
what cell secretes gastrin
g cell
where is gastrin secreted into
stomach antrum
what is gastrin’s target cell
parietal cells
how does gastrin reach parietal cells
secreted from stomach into systemic circulation and then delivered back to stomach via circulation.
what kind of receptor does gastrin bind to on parietal cells
CCK receptors
what is second messenger for gastrin
IP3/Ca2+
what stimulate secretion of gastrin from stomach
distension of stomach
presence of small peptides and AA
vagus nerve stimulation
what kind of receptors does Histamine bind to
H2 receptors
how does histamine reach its target cell
paracrine mechanism
what is the second messenger for histamine
cAMP
what blocks H2 receptors
cimetidine
when is little gastrin secreted
in response to a meal
when is big gastrin secreted
b/w meals (fasting)
what is gastrin’s response to a stimulus
Promotes H+ secretion by gastric parietal cells
Promotes growth of gastric mucosa
Inhibits gastric emptying
what stimulates gastrin release
A meal – Small peptides and AAs
Distention of the stomach
Vagal Stimulation (GRP)
what is potentiation
the ability of two stimuli to produce a combined response that is greater than the sum of the individual responses.
rate of H+ secretion is regulated by what
Ach
histamine
gastrin
working alone and together
what does cimetidine do
blocks H2
what does atropine do
blocks muscarine (muscarine antagonist)
how does potentiation relate to drug use for H+ release
if you block one pathway you could have bigger consequences than expected b/c you’re not just blocking that pathway you’re blocking the interaction b/w them
what are the three phases of gastric HCl secretion
cephalic, gastric, and intestinal
what nerve accounts for cephalic phase
vagus
cephalic phase accounts for how much of total HCl secretion
30%
what is stimulation for HCl secretion in cephalic phase
smelling and tasting, chewing, swallowing, and conditioned reflexes in anticipation of food
what are the two mechanisms that promote HCl secretion in cephalic phase
- direct stimulation of parietal cell by vagus nerve
2. indirect stimulation of parietal cell by gastrin
gastric phase accounts for how much of total HCl secretion
60%
what is stimuli for HCl secretion in gastric phase
distension of stomach
presence of proteins, AA, small peptides
what are the four mechanisms that promote HCl secretion in gastric phase
- direct stimulation of parietal cell by vagus nerve
- indirect stimulation of parietal cell by gastrin
- distension of stomach antrum → local reflexes → gastrin release
- AA and peptides stimulate G cells to release gastrin
what do alcohol and caffeine do regarding secretions
they stimulate gastric HCl secretion
intestinal phase accounts for how much of total HCl secretion
10%
when is HCl secretion inhibited
when it is no longer needed for activation of pepsinogen to pepsin
what happens with HCl when gastric contents PH is decreased
inhibits HCl secretion
what does somtostatin do to HCl
inhibits it, directly and indirectly
how does somatostatin directly inhibit HCl
binds to Gi which will inhibit adenylyl cyclase and reduce cAMP levels
how does somatostatin indirectly inhibit HCl
inhibits histamine release and gastrin release
what do prostaglandins do to HCl
lower HCl secretion
how do prostaglandins lower HCl secretion
activate Gi and inhibit adenylyl cyclase
what is pepsinogen
inactive enzyme precurosr
what pH is pepsinogen activated to pepsin
below 5
what do the salivary glands produce that has higher affinity for vitamin B12 than intrinsic factor has
R protein
what happens in duodenum with vitamin B12
R protein can no longer bind it b/c of pancreatic proteases, so intrinsic factor takes over
once B12 is absorbed into enterocytes what happens
it is transferred from IF to transcobalamin II where it will go to blood
what is pernicious anemia
your body can’t absorb enough vitamin B12 to make healthy RBC
what usually causes pernicious anemia
autoimmune disorder
describe the autoimmune disorder taht usually causes pernicious anemia
degeneration of parietal cell → loss of IF
what is another name for R protein
Haptocorrin
stimulation of mucus cells causes
exocytosis of mucin into lumen of stomach
what does prostaglandins do to mucous
stimulates the secretion of mucin
name the ways the body helps protect stomach from the acid
bicarb mucous tight epithelium blood flow HCl regulated
how does bicarb protect stomach from acid
helps to neutralize it
how does mucous protect stomach from acid
very thick and covers the epithelium. it also traps bicarb, so it keeps the cell surface to stay at pH 7
how does blood flow help protect sotmach from acid
removes toxic bi products from acid secretion
what things can harm the protective stomach barrier
NSAID (asprin)
stress
smoking
alcohol
what is zollinger ellison syndrome
gastrin secreted by pancreatic tumor
H+ secretion and gastrin levels increase
draw out the parietal cell and its HCl secretions
pg 23
omeprazole targets
target decreasing acid secretion
it will lower or eliminate acid secretion
what receptor does gastrin act on
CCK2
draw out the control of HCl secretion
pg 25
for little gastrin what is the minimum you can have to have it work
the last 4 AA
for CCK what is minimum you can have to have it work
last 5 AA
describe gastrin compared to CCK
the last 4 AA are the same
GRP stands for
gastrin releasing peptide
what is trophic
relating to feeding and nutrition
draw out control of HCl secretion
pg 28
somatostatin will stimulate Gi and inhibit
AC (Adenylyl cyclase)
what does ECL stand for
enterochromaffin-like
how is secretion of HCl turned off once chyme goes to duodenum
Somatostatin.
pH will go down and the decrease in pH will shut off parietal cells.
why does pH go down when food leaves stomach
food acts as buffer
where is haptocorrin released from
salivary gland
H. pylori causes 90% of
ulcers
NSAID stands for
non steroidal anti-inflammatory drugs
H pylori increases
gastrin levels
what does gastrin normally do?
HCl secretion
zollinger-ellison syndrome causes issue b/c
gastrin levels high because of tumor then it will act on stomach and secrete more acid