GI Flashcards
what is found in the lamina propria of GI mucosa
lymph nodules and capillaries
what enzyme is sued in the liver to produce cholesterol
acetyl coa
what is the clinical relevance of intrinsic factor
because it is necessary for B12 absorption, insufficieny will cause defects in DNA synthesis and lead to pernicious anemia (megaloblastic)
what membrane protein allows secreteion of HCO3 into the lumen
Cl-HCO3 exchanger on the apical membrane
orad stomach
caudad stomach
the upper part
lower part
zollinger-ellison disease
a gastrin producing tumor that causes excessive production of H+
what is the purpose of emulsification
to break particles into smaller pieces
what properities of the gastic mucosa make it a good barrier to prevent peptic ullcers
tight junctions to prevent acid penetration
hydrophobic to prevent ionized water soluble molecules from entering
how is Na absorbed and K secreted in the large intestine
what happens in diarrhea in relation to K secretion
passive channels
high flow rate of K into the lumin causes hypokalemia
what is the driving force behind H2O absorption in the GI tract
how else is water absorbed
high osmolality in the intercellular spaces between enterocytes
bulk transport
three phases of swallowing
oral
pharyngeal
esophageal
what are the three phases that regulate gastric secretion
cephalic
gastric
intestinal
wha three structures are found in the muscularis propria
circular muscle
lognitudinal muscle
myenteric plexus
what enzyme will absorb free amino acids in the small intestine
Na/AA symporter
what drug will inihibt the stimulating effect of muscarinic receptors on the proton pump
what does it do
atropine
it stops ACh from binding to muscarninc receptors
what does the submandibular gland secrete
mixed serous and mucous secretion
what is the parasympathetic effect on gastric emptying
sympathetic
PNS enhances peristalsis
SNS inhibits peristalsis
what specific chemical is released in response to gastric emptying of lipids into the duodenum
what cells secrete it
cholecystokinin
I cellls
what happens in the cephalic phase of gastric secretion
whhat percent of acid secretion is produced by this
conditioned response sends efferent signals to the stomach before food arives from the limbic system via the vagus nerve
40%
two types of epithelium found in the GI mucosa and their function
columnar: barrier, enzyme production, absorption
goblet: secretion of mucus
symptoms associated with a motility disorder
heartburn
stomach pain
cramping
nausea
vomitting
constipation
diarrhea
what is the impact of intraabdominal pressure on defectation
increased pressure facilitates defeccaton, especially during forced expiration
what is the driving for behind CHO absorption in the jejunum and ileum
Na/CHO symporters on the apical membrane that follow the Na gradient set up by the Na/K pump on the basolateral membrane
what are the hormone GI peptides
where are the secreted
what is the target
gastrin, CCK, secretin, gastric inhibitory hormone
from the stomach into the splanchnic and systemic circulation
either GI tract cells or distant cells
what happens during the emptying phase of the gastric pump
the liquids in the antrum are expelled into the duodenum while the large particles are left in the bulge of the terminal antrum
how often does the antrum contract in a fed state
how does this change in a fasted state
3 contractions/min
the antrum will be still for 2-3 hours, then have 10-20 minutes of intense contractions with relaxed pyloric sphincter, followed by another quiet period
three actions of lipid metabolism in the liver
cholestrol synthesis to form bile salts
triglycerides and VLDL
fatty acid metabolism for ATP or Ketones
what cells secrete histamine
what does it do
ECL cells in the H+ secreting region of the stomach
stimulates H+ secretion by parietal cells
what deficiency is the root cause of disorders associated with CHO digestion
Lack of dissacharidases (lactose intolerance)
four functions of the GI system
mix and move food
digest mechanically and enyzmatically
absorb nutrients from food
excrete by products
what is the RMP of smoothmuscle in the GI
-50 to -60 mV
where do phasic contractions occur in the GI tract
esophagus, antrum of stomach, small intestine
what is the direction of bile flow in the liver compared to blood floe
blood flow goes from the portal triad and sinusiods to the central vein
bile flows from the hepatocyes into bile cannaliculi and into the bile duct
what is the migrating myoelectric complex
the pattern of muscle contractions during fasting
where are peptic ulcers most common
where else can they occur
when will this cause bleeding
the duodenum
the antrum of the stomach and lower esophagus
when the ulcer penetrates to the submucosa
which pancreatic fat enzyme is secreted in its active form
cholesterol ester hydrolase
craniosacral = ____
thoracolumbar = ____
PsNS
SNS
5 effects of the CCK
contraction of the gall bladder
secretion of pancreatic enzymes
secretion of HCO3 from the pancreas
growth of exocrine pancreas and gallbladder
inhibition of gastric emptying
what is the end produce of protein digestion in the Gi tract
dipeptides and amino acids that are absorbed in the small intestine
what pancreatic enyzme will break down carbohydrates
amylase
how is lipase-bile converted into lipase-colipase
procolipase from the pancreas is converted to lipase by tyrosine, which removes bile salts from lipase and binds with it
what part of the enteric nervous system is found in the submucosa
the submucosal plexus
what is the function of the enteric nervous system
integrate the motor and secretory functions of the GI tract
where are mucus cells in the stomach and what do they secrete
antrum
mucus and pepsinogen
what is the basic function of the large intestine
reabsorption of water and elimination of waste
what is the empty volume of the stomach
what volume can it hold before intramluminar pressure begins to rise
50mL
1000mL
why is bile important
it is needed for the digestion of lipids and fat soluble vitamins
four functions of GI peptides
motility of smooth muscles and sphincters
secretion of enzymes, fluid, electrolytes
growth
regulation of other peptides
how does food content change gastric emptying
liquid food empties faster than solid
CHO faster than protein faster than fat
where are ICC cells found
what is their function
how are thei regulated
muscularis externa
responsible for slow wave potentials in the GI
the action of other ICCs, SMC, and the ENS
what are the neurocrine GI peptides
where are they secreted
ACh, NE, VIP, gastrin releasing peptide, neuropeptide Y, and substance P
into the GI tract from neurons following an AP
what currents work to produce the plateau in phase 3
inward Ca and outward K
what is the fucntion of norepinephrine in the GI tract
relaxation in the SMC wall
contraction of sphincters
stimulation of salivary secretion
four basic digestive actions
motility
secretion
digestion
absorption
where are parietal cells found in the stomach
what do they secrete
body
HCl and intrinsic factor
propuslion
controlled movement of the contents of the GI tract froms stomach to large intestines
how is HCl secretion regulated in parietal cells
G cells
vagus nerve stimulation
ECL cells
5 functions of cholestrol in the body
cell membranes
Vitamin D
hormones
myelin
bile salts
what is the function of crypts in the large intestine
secretion of mucus
what determines if the pattern of action for SMCs will be peristalsis or segmentation
the orientation of the fibers (circular or longitudinal)
where are chief cells in teh stomach
what do they secrete
body
pepsinogen
what type of glands make up 90% of the pancreas
exocrine glands
what provides extrinsic innervation to the GI tract
autonomic nervous system
how often does the small intestine contract
what are the contraction patterns
12/min (constant)
primary: segmentation, secondary: peristalsis
how is fat absorbed into the lymph after digestion in the small intestine
lacteals
how do ductal cells modify the compostion of saliva
extraction of Na and Cl
addition of K and HCO3
how are CHO and proteins absorbed after digestion in the small intestine
capillaries
four pancreatic enzymes that break down proteins
trypsin, chymotripsin, carboxypeptidase, elastase
where are G cells in the stomach and what do they secrete
antrum
gastrin
four regions of the stomach
fundus
body
antrum
pyloris
what are the endocrine cells of the pancreas
what do they do
islets of langerhans cells
secretes insulin and glucagon
what are the primary functons of motility in the small intestine
Digestion and absorption of nutrients
two types of motility in the large intestine
haustral movement
mass movement
where does intrinsic regulation of the GI tract come from
ENS
three functions of bacteria in the GI
protection against pathogens
metabolic functions
vitamin production
what digestive processes happen in the large intestine
none, water and Na are reclaimed, K is secreted, undigestable wastes are broken down by bacteria
function of secretion in the GI tract
producting liquid to lubricate the canal and aid in the process of digestion
what is the function of gastrin releasing peptide in the GI tract
releasing gastrin
what are the functions of HCl in the stomach
kills microorganisms
activates pepsin
reduces gastric emptying rate
what is controled by the enteric nervous system
intrinsic innervation of the GI
pharmacomechanical coupling
release of CA from the SR through G protein coupled receptors with no change in membrane potential
how do ECL cells regulate HCl production in parietal cells
producing histamine which stimulates H2 receptors to produce G protein and cAMP, increasing proton pump activity
what causes duodenal ulcers
rapid gastric emptying will cause too low of a pH to be effectively buffered by the duodenum, leading to ulcer
T/F there are no vili in the large intestine
true
two parts of the glandular structures in the mucosa of the stomach
gastric pits
gastric glands
gastrocolic reflex
the intiation of peristalsis in the GI tract caused by eating that can lead to defecation
three functions of bile salts
emulsification of fat
micelle formation to make fats soluble
removal of waste products (bilirubin)
what happens during phase 4 that allows for repolarization of SMCs in the Gi tract
voltage gated Ca channes close, activation of Ca gates K channels
describe the process of dysfunction in lactose intolerance
ingested lactose is not broken down in the small intestine
lactose in the large intestine feeds bacteria
bacteria ferment lactose to produce CO2, H2, and carbon metabolites
H2O is taken out of the body into the colon
patterns of GI motility
propulsion
trituration
mixing
reservoir functions
phasic contractions
three types of ducts found in salivons
intercalated ducts
striated
excretory
what triggers esophageal peristalsis
stimulation of stretch receptors in the wall that trigger local and CNS distension reflexes
what extracts bile slats from portal blood
hepatocytes
what is the relationship between flow rate and salivary composition
the higher the flow rate the less ionic modification can take place
two conditions that can cause osmotic diarrhea
ingestion of a poorly absorbed substrate such as epsom slats
malabsorption (lactose intolerance)
T/F the ENS can regulate all of the GI functions indepenently
true
what are the common manifestations of sjogrens syndrome
dry mouth
difficulty chewing and swallowing
candida
rotten teeth
what are the three main ways teh GI breaks down proteins
Pepsin in gastric juice
pancreatice enzymes
amino peptidases in the small intestine
what must accompany esophageal peristalsis
relaxation of the esophageal sphincter
why are micelles important to lipid digestion
because they are water soluble and will difuse across the apical membrane
portal triad
the trio of portal vein, hepatic artery, and bile duct that runs through every level of organization of the liver
what is the function of villi and microvilli in the small intestin
increase surface area of absorption
what is secreted by acinar mucous cells in the salivon
mucin
what causes gastric ulcers
regurgitation of duodenal contents can, because they are basic and gastric mucosa is resistant to acid, not base
where is B12 absorbed
the small intestine
what cells secrete Gastric inhibitory peptide
what is the secretion stimulus
K cells in the small intestine
fat, carbs, amino acids
T/F muscle contraction is always present in the GI tract
true, but the magnitude of contraction depends on the presence of an AP
describe primary perstalsis
what part of the brainr regulates this
perstalsis that follows the distention reflex in the esophagus
the brain stemm
what is the purpose of CCK inhibition of gastric emptying
ensures adequate time for digestion and absorption
describe the “alkaline tide”
HCO3 from the parietal cells is absorbed into venous blood in the portal system and released into the duodenum via the pancreas
what parts of the stomach serve as a reservior
what allows them to do this
the fundus and upper body
relaxation of tonic contractions in the SM to distend the cavity
where is 92-97% of the diet absorbed
the small intestine
how is the prophospholipase converted to phospholipase
trypsin in the small intestine
gastric punp
the contraction that periodically propels a portion of chyme through the pylorus int the duodenum
what is the serosa/adventitia
a layer of simple squamous epthelium furthest from the lumen in the GI tract that has little conective tissue
during fasted contractions of the antrum, what will happen to indigestable objects in the stomach
they will be pushed into the duodenum
why is pancreatic venous blood acidic
because H+ is secreted through the basolateral membrane into the blood
what digestive processes happen in the mouth
chewing and break down of CHO by salivary amylase
how do slow waves from the ICC induce peristalsis
they release a slow action potential that acts a pacemaker current and depolarizes SMCs when threshold is reacted
three CHO metabolic functions of the liver
gluconeogenesis
glycogenolysis
glycogenesis
what stimulates the gastrocolic reflex
what are the chemical/neurological mediators
what happens in response
stretch in the stomach and byproduct in the small intestine
gastrin and ANS
forceful peristaliss in the colon which increases rectum pressure and encourages the defecation
two conditions that will cause a deficiency in proteases
chronic pancreatitis and cystic fibrosis
what is the function of trypsin
to activate other proteases
what is the only site for the secretion of intrinsic factor
what does IF do
parietal cells of teh stomach
absorps vitamin b
what is the preganglionic parasympathetic neurotransmitter
postganglionic
acetylcholine for both
what vitamin stored in the liver is important for Ca absorption
Vitamin D
what is the role of the stomach in lipid digestion
it breaks fat into smaller parts and empties at a controlled rate into the small intestine to allow for proper absorption
what is the function of substance P in the GI tract
contraction of smooth muscle
stimulation of salivary secretion
what digestive processes happen in the esophagus
none, food bolus is sent to the stomach via peristalsis
what is the function of segmentation
how does it work
to mix chyme and expose to enzymes and secretions
circular muscle contracts and splits the chyme, then the two halves merge during relaxation
when would secondary peristalsis occur
when primary peristalsis is not enough to move food through the esophagus
disaccharidases
enzymes located at the brush border of teh small intestine used to break dissacharides into glucose
causes of maldigestion GI tract
pancreatin insufficiency
zollinger ellison
cholestasis/bile deficiency
lack of brush border enzymes
nutrient digestion by bacteria overgrowth
what is the function of ducts in the salivon
modification of fluid compositon
is saliva typically basic or acidic
basic (7-8)
what are the AP phases of a GI SMC
Phase 0: resting MP (-50 to -60) with an outward K
Phase 1: Upstroke
Phase 2: transient repolarization
Phase 3: plateau
Phase 4: repolarization
what happens to bile salts after lipids are absorbed
they are recirculated into the enterohepatic circulation
two GI disorders related to abnormal motility
Duodenal and Gastric ulcers
what are the two types of electrically coupled cells in the GI tract
smooth muscle cells
interstitial cells of cajal
three proteins found in saliva with their function
amylase (breaks down starch into maltose)
lysozyme and IgA (antimicrobial)
lactoferrin (binds Fe to suppress bacteria
T/F acinar cells in the salivon secrete mostly isotonic lfuid
what bout the ducts
true
the secrete a hypotonic fluid
stellate cells
cells that store lipid droplets that contain vitamin A
what is the functon of mixing movement
mixxes food and enzymes to facilitate digestion
what are the exocrine cells of the pancreas
what do they do
acinar cells and ductal cells
secretes digestive enzymes into the dudodenum
what is the action of acetylcholine in the GI tract
contraction of the SMC in the wall
relaxation of sphincters
stimulation of secretions
what two reflex mechanisms increase or decrease saliva production
simple reflex
conditioned reflex
How do g cells regulate HCl secretion by parietal cells
gastrin produced CCK, producing G protein and IP3Ca to stimulate the proton pump
what is the function of the acini in the salivon
what are the two cells that make up this structure
secretion
serous cells and mucous cells
mass movement leads to distention of the rectum, which does what
when will this lead to defecation
provides the urge to crap
reflexive relaxtion of the the internal anal sphincter and contraction of the rectum and sigmoid colon
if the external anal sphincter is relaxed
what are the two main enyzmes that absorb Na in the GI tract
how is the gradient established
Na/glucose and Na/AA symporter
Na/K pumps on the basolateral membrane
two enzymes secreted in gastric juices
protease, gastric lipase
how does the vagus nerve regulate HCl secretion by parietal cells
acetylcholine stimulates muscarinic receptors, producing g protein to produce IP3Ca2, which stimulates the H/K proton pump
in what part of the GI are slow waves always present
small intestine
what is found in the submucosal layer of the GI tract
connetive tissue
blood
glands
submucosal plexus
how is the constant movement produced by smooth muscle and ICC cells in the GI regulated
nerves, hormones, paracrine substances which can increase or decrease activity
three major salivary glands
parotid gland
submandibular gland
sublingual
T/F submucosa is present in the small and large intestines but not into the esophagus
true, it is also sparse in the stomach
what are two inbitory pathways for the proton pump
somatostatin and prostaglandins will both produce g proteins that inhibit cAMP production and decrease pump activity
what are five proteases of the Gi tract
trypsin, chymotrypsin, elastase, carbpxypeptidase A and B
three layers of GI mucosa
epithelium
lamina propria
muscularis mucosa
what is the function of somatostatin in the GI ttract
inhibition of GI hormones
inhibition of H+ secretion
what are the receptors that feed into the ENS
autonomic nerve receptors in the CNS
mechano and chemoreceptors in the the mucosa
what is the function of the migrating myoelectric complex
to empty the stomach of any residue from the last meal
what cells secrete CCK
what is the secretion stimulus
I cells of the small intestine
ingested fatty acids or small peptides
why is the size of micelles important
they are smalle enough to be absorbed past the apical membrane
what is the purpose of carbonic anhydrase in ductal cells
what will happen to the components
it breaks carbonic acid into HCO3 and H+
H+ is exchanged with Na on the basolateral membrane
HCO3 is exchanged with Cl on the apical membrane
why is there a high osmolality in the intercellular spaces between enterocytes
because a lot of sodium is secreted into this space
which of the three regulatory pathways of gastric secretion is inbitory
the intestinal phase
acid and fat in the duodenum stimulate cells in the small intestine that will inhibit gastrin secretion and decrease empyting rate
what is the function of the ENS
controls contractile, secretory, and endocrine functions of the GI
how does pH effect gastric emptying rate
activation of H+ receptors in the duodenum reduce gastric emptying to allow for buffering by pancreatic HCO3
cholera causes what type of diarrhea
secretiry diarrhea from cholera toxin
what cells secrete somatostatin
what is the stimulus
D cells in the gastric antrum
decreased luminal pH
three pancreatic enzymes that break down lipids
lipase/colipase, phospholipase, cholesterol esteras
what is the state of the colon with no stimulus
what happens after feeding
what happens during mass movement
a quiet colon or haustral shuttling with no net movement of chyme
increased contractions shuttle chyme from one haustra to the next
there is multihaustral propulsion
E-C coupling
the activation of Ca channels via action potentials
what cells secrete secretin
what is the secretion stimulus
S cells in the duodenum
H+ and fatty acids
cystinuria
a genetic disorder with the lack of a transporter for di-basic AAs
what are the fat soluble vitamins
how are they absorbed
A, D, E, K
the same as lipids
what converts stellate cells into myofibroblasts
what will myofibroblasts do
inflammation
secrete collagen and extracellular matrix into the perisinusoidal space
why is motility of the GI tract important
grinding, mixing, and fragmenting digested food to prepare it for digestion and absorption, then movement throough the GI
digestions
breaking down proteins, fats, and carbs in the GI traft
the reservior function of the stomach is mediated by what reflex
afferent and efferent fibers of this reflex are carried by what nerve
vagovagal stretch reflex
the vagus nerve
what two structures make up the myenteric plexus
submucosal and myenteric plexus
what happens if the external anal sphincter doesn’t relax in response to the urge to defecate
the urge subsides
what is the final product of lactose intolerance
osmotid diarrhea caused by CO2, H2, and carbon metabolites
what will inhibit the secretion of gastrin
low pH in the stomach
what is secreted by serous cells in the acini
watery fluid
digestive enzymes (amylase)
what digestive processes happen in the small intestine
chemical digestion of macronutrients is completed and the products absorbed
how much fluid is absorbed in the small intestine vs the colon
80% vs 20%
what are the extrinsic factors that regulate the ENS
ANS
neuotransmitters
hormones
inflammatory mediators or stress factors
three types of GI peptides
hormones, neurocrines, paracrines
why are parietal cells considered polar
they have different membrane proteins on the apical and basolateral membranes
four things that happen in the large intestine
absorption of H2O, Na, Cl
digestion and metabolism of remaining CHO
synthesis of vitamin K and B vitamins by flora
bacteral fermentation that produce gases and organic acids
causes of malabsorption in the GI tract
celiac sprue
gastronenteritis
crohns
lymph obstriction
two hormones found in gastric juices
gastrin and intrinsic factor
what controls gastric emptying rate
pH and food contents
what regulates the enzymatic secretion from acinar cells
CCK and Ach
what channels open during Phase 1 to create upstroke
voltage gated Ca and K channels
what is the function of secretin
promotes the secretion of pancreatic HCO3 to neutralize acid and inhibits the effect of gastrin on parietal cells
four Gi hormones
Secretin, GIP, Gastrin, CCK
what fat soluble vitamins are stored by the liver
A, D, K
what is the paradox of lipid absorption
the body goes through a lot of troube breaking fat into micelles and chol/TF/PL, then builds them into large molecules before absorbing them
describe the series of contractions that produces peristalsis
circular muscle behind the bolus pushes forward
contraction of longitudinal muscle and relaxation of the circular muscle ahead of the bolus makes space
what is the first step of protein digestion
activation of trysinogen into trypsin by the brush border enzyme enterokinase
where does the phasic contraction of the gastic (antral) pump start
why is the pump necessary
in the middle stomach
mixiing and trituration of food
where are minerals absorbed in the GI tract
the small intestine
what system plays a roll in regulation of all ENS functions
parasympathetic nervous system
name four substances found in saliva
water
mucin
proteins
salts
what is the function of striated and excretory cells in the salivon
they modify the ionic compositon of saliva
what drives the conditioned reflex in regards to salivation
thinking about, seeing, or smelling food
what happens in the gastric phase of regulation of gastric secretion
what percent of acid is secreted this way
distention in the stomach activates long and local reflexes in the stomach, increasing production of ACh, histamine, and gastrin to increase HCl production
what is the functon of zymogen granuales in acinar serous cells
production and storage of amylase
what is the process of breakdown of lipids after absorption into enterocytes
micelles are broken down into cholesterol, monoglycerides, phospholipids, and free fatty acids
fats are then formed into cholestrol, triglycerides, and phospholipids
cholestrol, triglycerides, and phospholipids are used to form chylomicrons
define a tonic contraction
what happens during this time
when the contraction produced membrane potential of a slow wave is not enough to breach threshold
no AP is generated and the muscle undergoes small contractions with incomplete relaxations
what regulates motility of the small intestine
inhibitory and excitatory impulses from the SNS or PNS transmitted through the enteric nervous system
describe the process of B12 absorption
dietary B12 is released from food by pepsin
free B12 binds to R protein in salivary juice
pancreatic proteases degrade R protien, allowing B12 to be picked up by intrinsic factor
intrinstic factor-B12 is absorbed in the iluem
interstitial cells of cajal
pacemaker like cells in the GI tract that contract spontaneously
absorption in the GI tract
the process by which the products of digestion are absorbed into mucosa and enters the lymph or blood
how much fluid is secreted by the stomach each day
what is the pH
2-2.5L
1-4
three different names for heartburn
GERD
Pyrosis
Esophagitis
what is secreted by the intercalated ducts of the salivon
epidermal growth factor
ribonuclease
amylase
proteinases
what the preganglionic sympathetic neurotransmitter
what is the post ganglionic
acetylcholine
norepinephrine
what is the break down of cholestrol in terms of where it is produced in the body
85% is produced by our own cells
15% is taken from food
where is bile ejected into
the small intestine
two sources of blood flow to the liver
portal vein from the GI tract
hepatic artery from the celiac artery
what happens during the retropulsion phase of the gastric pump
large partiles are pushed back into the body and the antrum is cleared
what digestive processes happen in the stomach
mechanical digestion of food via churning
chemical breakdown via pepsin and HCl
6 functions of the liver
detoxification of drugs
CHO metabolism
Protein metabolism
lipid metabolism
bile formation
removal of RBC’s and ammonium
what does the sublingual gland predominately secrete
mucous (70%)
T/F the ENS can function with or without autonmic regulation
true
three unique features of the GI tract
large population of bacteria
well developed local immune system
enteric nervous system for regulation
what is secreted by gastric glands
what is the compositon
gastric juices
Acid, enzymes, mucus, horomes
what is sjogrens syndrome
what is the result of this
a chronic autoimmune disorder where T and B cells attack salivary, lacrimal, or other exocrine glands
ductal lumen narrowing and atrophy of the gland
what simtulates secretion from ductal cells
what is the major stimulant
CCK, Ach, and secretin
secretin
what is the function of Vitamin A
important for vision (forms photoreceptors)
what is the sympathetic response that increases saliva production
NE stimiulates beta adrenergic receptors in acinor or ductal cells by producing cAMP
what type of contraction allows for reserrvior functions in teh GI
where is this function found (4)
tonic contrations
the lower esophagus, upper stomach, ileocecal valve, and internal anal sphincter
what is the chemical reponsible for most of the fat digestion in the small intestine
pancreatic lipase
what is the simple reflex
what will produce the strongest response via this reflex
salivation based on whats in the mouth
citric acid
what is the primary enzyme responsible for absorbing digested protein
H+/di - tripeptide symporter
what are the effectors of the GI tract
smooth muscle
exocrine galdns
endocrine galnds
what is the function of Vitamin K
synthesis of clotting factors II, IIV, IX, and X
4 plasma proteins formed by the liver
fibrinogen
albumin
prothrombin
trasnferrin
are ducts high or low in flow rate
low 1mL/min
T/F the SMCs of the GI function independent of each other
fallse, they function as a syncytium
two GI paracrines
Somatostatin, Histamine
two functions of chewing
reduce size of food particles
mix food with amalyse and saliva
two types of esophageal peristalsis
primary
secondary
what are the two types of GI contractions
tonic and phasic
two mechanisms that drive GI tract motility
E-C coupling
pharmacomechanical coupling
describe the muscular actions needed for defecation
relaxation of the puborectalis and the internal anal sphincter
contraction of the rectum and the anal canal
relaxation of the external anal sphincter
what four events must happen for lipid digestion
secretion of bile and lipases
emulsification by bile salts
enzymatic hydrolysis by lipases
micelle formation with bile salts
what are the five major secretory areas of the GI tract
mouth
stomach
pancreas
liver/gallbladder
small intestine
what are the functions of gastric motility
reservior
mixing, dividing, emptying in the lower stomach
contractions in the antrum open the pylorus
what structure helps enhance the local immune system in the GI
where is it found
peyers patches
ileum
how often is mucus secreted
how much is secreted each dayq
it is continuous in varying amounts
1-2 L day
what does the parotid gland secrete
serous secretion and amylase
describe the vagovasal flex in the stomach
postganglionic peptidergic vagal efferent fibers release vasoactive intestinal peptide (VIP) which relaxes the cardiac sphincter and smooth msucle in the orad stomach
describe the mechanism of HCl secretion by parietal cells
CO2 and H2O are formed into carbonic acid with carbonic anhydrase, which dissociates into H and HCO3
H is pumped into the lumen of the stomach via H/K exchanger on the apical surface
HCO3 is sent into the blood via HCO3/Cl exchanger
Cl passivly diffuses through channels into the lumen to form HCl
what cells secrete gastrin
what is the trigger stimulus
what are the effects
G cells
protein, dstomach distention, vagal stimulaton
promotes H secretion by parietal cells, stimulates growth of gastric mucosa
common cuases of peptic ulcers
H pylori, smoking, alcohol, NSAIDs, stress, ischemia
what happens during the propulsion phase of the gastric pump
thre is a rapid flow of chyme with delayed flow of large particles towards the pylorus
what are the three phases of the gastric (antral) pump
propulsion
emptying
retropulsion
define a phasic contraction
what will cause stronger contractions
a contraction started when the slow wave is enough to depolarize the SMCs and produce an AP
more APs on top of the slow wave produce stronger contractions
what is the storage capacity of the stomach
around 4 cups or 1L
is defecation reflexive or voluntary
both, both sphincters have to be relaxed in order to defecate
trituration
the crushing and grinding of ingested food
what element is most important for the absorption of monosaccharides in the small intestine
why
sodium
because Na/glucose and galactose symporters are important cell proteins in the process
what is the function of mucus in gastric juices
protecting the stomach from dehydration and helping form chyme
what are the paracrine GI peptides
where are they secreted
what is their target
somatostatin and histamine
in the endocrine cells of the GI tract
other cells with in the same tissue that secretes them
define peristalsis
a progressive wave of contractions along the wall of the GI tract from esophagus to large intestine
what are the four layers of te GI tract
mucosa, submucosa, mucularis propria, serosa/adventitia
what is the basic unit of the salivary gland
what are the two parts of this structure
salvion
acini and ducts
what happens to micelles as they are absorbed
the lose their bile salts
they are broken into triglycerides and protein, then formed into chylomicrons
chylomicrons are secreted into blood
motility
the movement of the GI system that transmits contents from mouth to rectum
three compnonents of bile
bile salts, bilrubin, cholestrol
kupffer cells
liver macrophages that line the hepatic sinusoid and ingest bacteria
where is the integration center for defecation found
does it take input from high CNS structures
the sacral spinal cord
yes
four types of diarrhea
decreased surface area (celiac sprue)
osmotic diarrhea
secretory diarrhea
intestinal infections
what is the PsNS response to the conditioned salivary reflex
what is the neurotransmitter
parasympathetic will increase saliva secretion in response to food, nausea, smells
decrease production due to dehydration, fear, sleep
ACh, which stimulates muscarinic receptors with atropine
how does bile function to digest fat
it emulsifies liquid to prepare them for digestion, then packages them into micelles for transport
what current provides transient repolarization during phase 2
`transient outward K rectifiers
what is mucin
a glycoprotein found in saliva that helps thicken saliva
how is SMC contraction started in the GI tract
how is the AP conducted
two orientations of SMC in the GI
response to membrane potentials created by teh ICC
gap junctions
circular and longitudinal
what do the acinar and ductal pancreatic cells do
acinar cells secrete pancreatic enzymes
ductal cells secrete HCO3 soloution
