This is the substance called in the stomach when food mixes with gastric acid?
Chyme
This is the reflex that causes relaxation of the stomach to allow more food in the stomach when the stomach is stretched.
Vasovagal reflex (X)
This the wave that starts at the top of the stomach and goes down to the bottom every 15-20 seconds.
Constrictor wave
What is the name of the “drive” for the constrictor waves to begin?
Basic electrical rhythms (BER)
When the constricting wave pushes food to the pyloric sphincter, how much food is passed through?
Just a squirt. The remaining moves back up towards the body of the stomach.
When do hunger pangs start?
when there is no food in the stomach for several hours
When you’re hungry, what is the name of the process that causes your tummy to rumble?
Interdigestive migrating myoelectric complex, which empties out the stomahc
What is the thickest area of the stomach wall?
Pyloric sphincter
Since the pyloric sphincter is always super contracted, what type of foodstuff can pass through?
Only fluids and chyme. Food has to get ground a lot in the stomach before it goes tot he duodenum.
This is a rare contraction to squeeze the stomach in a tight ring so that food can only go to the pylorus to be pumped to the duodenum.
Pyloric pump
What is the effect of stretching of the stomach wall due to a lot of food on gastric emptying?
It elicits greater pyloric pump action
Which gastric hormone promotres the pyloric pump activity?
gastrin
The duodenum can inhibit gastric emptying by what 3 neural mechanisms?
- enteric NS
- SANS ganglia
- PANS signals
How do duodenal neural mechanisms decrease gastric emptying?
by ihibiting pyloric pump and increase the tone of the pyloric sphincter
What is the effect of CCK on gastric emptying?
potent inhibitor. released when fat is present. inhibits gastrin
What is the effect of secretin on gastric emptying?
inhibits in response to excess gastric acid in chyme
What is the effect of GIP on gastric emptying?
slows gastric motility when exposed to fat and carbs
In the fundus of the stomach, the oxyntic gland secretes which 4 factors?
HCL, pepsinogen, intrinsic factor, and mucus
Which cells in the oxyntic gland secrete mucus?
mucus neck cells
Which cells in the oxyntic gland secrete pepsinogen?
peptic/chief cells
Which cells in the oxyntic gland secrete HCL and intrinsic factor?
parietal cells
In the antrum of the stomach, the pyloric gland secretes which 2 factors?
mucous and gastrin
What is the “alkaline tide” that is formed when the parietal cell secretes HCl?
It’s the diffusion of bicarb into the ECF and blood when HCl is secreted into the stomach lumen.
What is the first ion that is pumped into the canaliculi lumen from the ECF during the formation of HCl?
Cl-
Then what happens to water inside the parietal cell?
Splits to OH and H+
How is the H+ then pumped into the canaliculi lumen?
Through and K+/H+ ATPase exchanger
Now what 2 ions do we have inside the canaliculi lumen?
Cl- and H+ –> HCl
So you put all this salt on 1 side of the cell (canaliculi side), so where does water go?
Into the canaliculi lumen
What about that OH- left inside the parietal cell? What does it combine with to form HCO3-?
CO2
So what happens if there is a process to stall the formation of HCl? Would the ECF fluid be more alkalotic or acidic?
Acidic because there is no HCO3- transported into the ECF fluid!
What do chief cells secrete again? Which gastric hormone?
Pepsinogen
What does pepsinogen form when it meets HCl?
Pepsin
What is the role of pepsin in the stomach?
Break down proteins
What would happen to protein breakdown in the stomach if you took a PPI or antacid?
wouldn’t happen as much cuz pepsinogen can only be cleaved at a pH of 1.8-3.5.
What are the 2 stimuli for pepsinogen release from chief cells?
- Ach from X
2. HCl from parietal cells
Which cells again secrete intrinsic factor?
Parietal cells
same ones that do HCl secretion
What happens if IF isnt secreted and B12 isnt protected?
B12 can’t cross the membrane in the ileum and then RBCs are unable to maturate in the bone marrow
What metal is taken up by DCT1 cells in the stomach?
Fe++
Histamine is secreted by what cells in the GI tract?
ECL cells
Histamine in the gut stimualtes which cells and subsequently the release of which factor?
Parietal cells to release HCl
Which hormone stimulates ECL cells to release histamine?
Gastrin
So when food is sensed by the stomach and gastrin is released, how can it cause more HCl to be released?
Gastrin stimulates ECL cells –> histamine released –> Parietal cell stimulation –> more HCl released
This is the reflex when the duodenum tells the stomahc to slow down a bit because of the presence of food in the duodenum.
Enterogastric reflex
The enterogastric reflex uses which neural pathways to talk to the stomach?
myenteric NS, SANS, or X to inhibit the pyloric pump
To break down proteins, pepsin is activated (we talked about this). Which other enzymes are activated by pepsin to break down proteins? (4)
Trypsin, chymotrypsin, carboxypolypeptidase, proelastase
This is the condition in which there is inflammation of the gastric mucosa.
Gastritis
What are the 2 most common swallowed substances to cause acute or chronic gastritis?
Alcohol and aspirin
In gastritis, the permeability of the mucosal barrier is greatly increased, causing damage to the mucosa by what substance?
HCl
This is the condition when the stomahc fails to produce HCl.
Achlorhydria
Achlorhydria can cause what to the stomach?
Atrophy
If there’s no acid in the stomach, what can’t you breeak down? Why?
Proteins cuz pepsinogen isnt cleaved by the acid
Why can achlorhydria lead to pernicious anemia?
cuz IF isnt released –> decrease in B12 absorption in the ileum
Where in the stomach does peptic ulcers most commonly occur?
Around the pylorus
OMG IVE HAD SO MUCH COFFEE LIKE MY FINGERS HAVE FEELINGS RIGHT NOW. SHHHHH PINKY FINGER. EVERYTHING WILL BE OK. JUST KEEP DOING YOUR THING YOU DIGITAL RUNT.
Sooooo a ulcer can form from what 2 causes?
- excess secretion of acid and pepsin
2. dimished protection of the gastroduodenal mucosal barrier
Which organism can penetrate the mucosal barrier, causing such ulcers?
H. pylori
Signals from the stomach to start the vomiting process are carried on what afferents to the brain?
SANS and X
What is the name of the area of the brain that causes vomiting upon stimulation?
Chemoreceptor trigger zone
Once stimulated, the chemoreceptor trigger zone causes what type of motion in the upper GI tract to get all that stomach crap out the wrong end?
Antiperistalsis
I HATE BRUSHING MY TONGUE CUZ HOLY CRAP IM LIKE TRIGGERING THAT SHIT LIKE EVERY TIME I DO IT. BUT I DO IT CUZ THATD BE NASTY IF I DIDNT. YA HEAAAAR?