Flashcards in Stomach 1 Deck (69):
name the two functional regions of the stomach (and their main parts)
proximal- fundus and proximal body
distal- distal body and antrum (pylorus)
the proximal region (orad stomach) is responsible for what?
receiving ingested meal
the distal region (caudad stomach) is responsible for what
contractions that mix food and propel it into duodenum
what are the three functions of the stomach?
what occurs in the stomach during food storage
proximal stomach relaxes to accommodate ingested meal- via receptive relaxation
pressure slowly returns to basal level
stomach can hold up to 1.5 L w/ little change in pressure
receptive relaxation (what is it, what mediates it, how is it abolished)
process by which the proximal stomach relaxes to accommodate ingested meal
mediated by vagovagal reflex
abolished by vagotomy
the vagovagal reflex is initiated by what?
distention of the stomach
what occurs in the stomach during mixing
presence of food causes distal stomach to increase contractions
this mixes food with gastric sections and reduces size of particles
food mixed into pasty consistency (chyme)
what is chyme?
semifluid mass of partly digested food passed from the stomach to small intestine (made during mixing in stomach)
what occurs in stomach during emptying
distal stomach contracts to propel food into duodenum
peristaltic contractions originate where and proceed how?
originate in pacemaker region (midstomach)
a peristaltic contractions move distally toward pylorus what happens to velocity and force of the contractions?
they both increase
retropulsion (what is it)
process by which most of chime is propelled back into the stomach to be mixed
due to wave on contractions closing distal antrum and pyloric sphincter before chyme reaches there
the wave of peristaltic contractions does what to distal antrum and pyloric sphincter
closes them before the chyme can reach there
what occurs during fasting (contractions wise and how often)
contractions called migrating myoelectric complexes occur at 90 minute intervals
migrating myoelectric complexes (what do they do)
occur every 90 minutes during fasting
clear the stomach of any residual food
cause hunger contractions if stomach has been empty for about 2 hours
how are migrating myoelectric complexes abolished
hunger pangs (when do they start and how long do they last)
start 12-24 hours after last meal
continue for about 3-4 days before subsiding
emptying of the stomach occurs when?
chyme decomposed into small enough pieces to fit through pyloric sphincter
following a normal mixed meal emptying of the stomach may take about how long, and is dependent on what?
about 3 hours
depends on type of food ingested
place the following in order of fastest to slowest in terms of emptying from the stomach:
carbohydrate-rich food (fastest of these three) > protein-rich food > fat-rich food (slowest of these three)
between liquids and solids which empty from the stomach fastest
the rate of emptying has what type of relationship with the pressure in the proximal stomach (which increases slowing during digestive period)
gastric emptying is controlled mostly by what?
signals from duodenum
gastric emptying is inhibited by what stimuli?
fat or protein digestion products
increases distention of proximal stomach
increase pressure in proximal small intestine
gastric emptying prevents what? (in terms of the flow of chyme)
prevents flow of chyme from exceeding ability of intestine to handle it
Gastroparesis (what is it, what does it produce, what causes it
impaired/ delayed emptying
produces symptoms of fullness, loss of appetite, nausea, vomiting
most common cause is diabetes
increased gastric emptying can cause what?
diarrhea (b/c increased osmotic load in small intestine)
duodenal ulcers (b/c stomach acid damages duodenum)
dumping syndrome (what is it, when is it common)
occurs when lower end of small intestine fills too quickly with undigested food from the stomach
common after surgery
dumping syndrome (what are the phases, when do they occur, and what are the symptoms)
early phase- occurs either during/right after meal (nausea, vomiting, diarrhea)
late phase- occurs 1-3 hours after meal (sweating, weakness, dizziness)
the symptoms of dumping syndrome are due to what?
too much fluid in intestine and hypoglycemia
based on secretory function what are the two regions of the stomach
oxyntic gland mucosa (located in proximal stomach)
pyloric gland mucosa (located in distal stomach)
oxyntic gland mucosa (located where and secretes what)
located in proximal stomach
pyloric gland mucosa (located where and secretes what)
located in distal stomach
in the oxyntic gland the surface mucous cells extend into what?
in the oxyntic gland the mucous neck cells (what do they secrete and what do they serve as)
serve as stem cells
in the oxyntic gland the stem cells proliferate and differentiate into what?
surface mucous cells
in the oxyntic gland the parietal cells secrete what?
in the oxyntic gland the endocrine cells secrete what?
products that regulate gastric function
in the oxyntic gland the chief (peptic) cells secrete what?
what are the 4 components of gastric juice that have physiological function
what begins digestion of dietary protein?
lack of or reduction in acid production leads to what? (in terms of the stomach and upper small intestine)
infections of the stomach and small intestine
what kills most bacteria that enter the stomach
pepsin is stored and secreted as what?
inactive precursor pepsinogen
pepsinogen is converted to pepsin by what?
gastric acid (HCl)
what begins digestion of proteins by splitting interior peptide bonds in proteins
what causes greatest increase in secretion of pepsin
the mucus of the stomach serves what purpose?
serves as a protective coating for stomach and lubricant and barrier between cells and ingested material
two forms: soluble and insoluble
the soluble for of mucus in the stomach is secreted from where, does what, and is present when?
secreted from mucus neck cells after stimulation by vagus nerve
mixes with other secretions of glands and lubricates chyme
not present in resting stomach
the insoluble/visible form of mucus in the stomach is secreted from where, as what, and what does it do?
secreted by surface mucus/goblet cells
secreted as gel forming unstirred layer over mucosa
traps dead cells from mucosa and forms protective coat
insoluble/visible form of mucus is secreted when?
by resting stomach
in response to chemical or physical irritation
what maintains the pH at the surface of the stomach nearly neutral
HCO3- trapped in the insoluble layer
what happens to insoluble mucus on contact with acid?
precipitates into clumps and passes into duodenum with chyme
insoluble mucus with alkaline secretions make up part of what barrier?
gastric mucosal barrier that prevents damage to mucosa by gastric contents
intrinsic factor (what is it, what secretes it, what does it do)
secreted by parietal cells of gastric mucosa
binds vitamin B12
where is vitamin B12 absorbed and what is required of the absorption to occur?
absorption occurs in ileum
intrinsic factor is required of the absorption
the absence of intrinsic factor results in what?
total gastrectomy patients require what?
injections of vitamin B12
parietal cells secrete what into the lumen of the stomach and what into the bloodstream
HCl into lumen of stomach
HCO3- into the bloodstream
the H+ secrete into the lumen across the cell membrane is in exchange for what and by what?
K+ in a 1:1 ratio by H+/K+ ATPase
where does the bicarbonate in the parietal cells come from?
CO2 generated by cell metabolism and then carbonic anhydrase
Cl- enters the parietal cell how and is secreted into the lumen how?
enters cell in exchange for HCO3-
secreted in to lumen through channel
alkaline tide (what creates it, where does it occur, and when)
HCO3- creates it in venous blood of actively secreting stomach by raising pH
chronic vomiting can lead to what?
K+ concentration is what in the gastric juice compared to the plasma
always zΩhigher concentration in gastric juice than plasma
ionic composition of gastric juice changes with what?
rate of secretion
at low (basal) rates of secretion what is the ionic composition of gastric juice
primarily NaCl from nonparietal secretions