Digestive System: Stomach- Fitz Flashcards
What does the soft palette and uvula close during swallowing?
The nasopharynx
Voluntary
What closes the glottis during swallowing?
Inhibition of respiration
Voluntary
Why do pills get stuck?
They lodge laterally to the esophagus in the pisiform recesses
What type of cartilage is found in the larynx?
Cricoid cartilage
The mechanism by which swallowing occurs in the esophagus
Peristaltic wave
The calcium binding protein that regulates free calcium in smooth muscle
Calmodulin
Smooth muscle contraction process
More Ca2+ activates myosin kinase and phosphorylates the myosin > myosin-P binds to actin causing a contraction > Ca2+ decreases and the kinase is inactivated
How does free Ca2+ travel from each cell?
Via gap junctions
What nuclei are involved with the NTS?
Nonvagal nuclei
Nucleus abiguus
Dorsal motor nucleus
When does the upper sphincter relax?
When the larynx is lifted
What types of fibers are behind the bolus?
Circular fibers
What type of fibers are in front of the bolus?
Longitudinal fibers
When does the lower esophageal sphincter relax?
As food approaches
What happens when there is a dysfunctional esophageal sphincter?
Regurgitation of stomach acid into the base of the esophagus
What is the site of esophageal cancer?
At the lower esophageal sphincter
What does the colon do?
Absorb water
What is the cephalic phase?
An emotional state, input from brain on the digestive system
Gets parietal cells working
What do parietal cells do?
Make HCl and initiate other cells to secrete their substances, leading to the gastric phase
What stimulates histamine to in turn stimulate the parietal cells?
Gastric
What things directly stimulate the parietal cells?
Histamine and enteric neural activity
What inhibits parietal cells once a certain level of HCl is reached?
Somatostatin
Which side is the stomach on?
The left side
What are rugae?
Infoldings on the stomach that allow it to stretch
Why are the muscles of the stomach in different directions?
To roll the food around
What is the antrum?
The body of the stomach
What converts pepsinogen from chief cell to pepsin?
HCl
Where is intrinsic factor made?
In the wall of the stomach
What does intrinsic factor do?
Absorption of vitamin B12 for RBC production
What does gastrin hormone do?
Release more gastric juice
Increase gastric motility
Relax pyloric sphincter
Constrict esophageal sphincter
What are G cells and what do they do?
They’re enteroendocrine cells that make gastrin
What are chief cells and what do they do?
They’re zymogenic, meaning they make precursor molecules. Namely, pepsinogen and gastric lipase
What do parietal cells do?
Increase surface area for H+ and Cl pumps, makes HCl
What do mucus neck cells do?
Coat surface cells with mucus as a surface layer to protect
Trap bicarbonate at surface of epithelium
Enzyme catalase for forming bicarbonate
Carbonic anhydrase
Regulation of HCl occurs via:
: blocking histamine receptors
Molecules that stimulate HCl production
Histamine: enteric nerve
Gastrin: enteric nerve
Ach: vagus nerve
Molecule that inhibits HCl production
Somatostatin
What are enteric-chromaffin like cells and where are they located?
They allow for the production of HCl via their Ach and gastrin receptors. They’re located in the submucosa below the parietal cells
Where does the stomach get lots of its vascularizarion?
The abdominal aorta
What is the cephalic phase?
Initial phase stimulating the vagus to increase parietal cells and gastrin production via Bombesin (gastrin-releasing peptide)
30%
What is the gastric phase?
60% of digestive process
pH mediates gastrin
Vasovagal stretch occurs-> increase gastrin and acids
What molecules increase gastric acid in the gastric phase?
Proteins
Tryptophan
Phenylalanine
What happens to stomach volume and pH after you finish a meal?
Stomach volume shoots up
pH shoots up
About how long does it take for the stomach to empty after a meal?
2-4 hours
Where do gentle mixing waves of the bolus occur?
Fundus stomach where the food is turned to chyme
Where do medium mixing waves occur?
From body of stomach to pyloric stomach
Where do the intense mixing waves occur?
Near the pylorus
How does HCl initiate protein digestion?
It denatures molecules
What does gastric lipase do?
Splits triglycerides in milk fat
What kills microbes in food?
HCl
How thick is the mucus layer of the stomach?
1-3mm thick
What causes ulcers?
Bacteria that breakdown the stomach’s mucoid coating
What happens during the intestinal phase?
Stretch receptors activated in duodenum because of the presence of chyme
Alerting the pancreas (Pacinian corpuscles)
Chemoreceptors detect FAs and glucose in duodenum
What is CCK?
Comes from endoendocrine cells of duodenum
Decreases gastric juices
Triggers gall bladder
What is secretin?
Made in duodenum
Shuts down stomach digestion by decreasing peristaltic movement
What occurs at the junction of the pyloric sphincter and the duodenum?
Release of duodenal enzymes
Pancreatic and common bile duct enter here to increase in pH for alkaline environment for duodenal enzymes
What happens when a meal is high in fat?
Secretions by enterogastrones
stop the gastric exiting because too much fat or protein is detected in the duodenum
What do GI hormones do?
Regulate water and electrolyte secretion
Enzyme secretion
Contraction and relaxation of smooth muscle
What opens the sphincter of Oddi?
CCK
Where is gastrin produced?
Antrum of stomach
What stimulates gastrin release?
AAs, peptides in stomach, parasympathetic nerves
What inhibits gastrin release?
Acid in stomach
Somatostatin
What does gastrin do in the stomach?
Stimulate acid secretion
Stimulate motility
What does gastrin do in the pancreas, liver, gall bladder?
Nothing
What does gastrin do in the small intestine?
Stimulate ileum motility
What does gastrin do in the large intestine?
Stimulate mass movement
What stimulates CCK release?
AAs in SI
FAs in SI
What does CCK do in the stomach?
Inhibit acid secretion
Inhibit motility
What does CCK do in the pancreas?
Aid secretin’s stimulation of bicarbonate secretion
Stimulates enzyme secretion
What does CCK do in the liver?
Aid secretin’s stimulation of bicarbonate secretion
What stimulates secretin release?
Acid in SI
What does secretin do in the stomach?
Inhibit acid secretion
Inhibit motility
What does secretin do in the pancreas?
Stimulate bicarbonate secretion
Aid CCK in stimulating enzyme secretion
What does secretin do in the liver?
Stimulate bicarbonate secretion
Where is GIP produced?
Small intestine
What stimulates GIP release?
Glucose in SI
Fat in SI
What does GIP do in the pancreas?
Stimulate glucose secretion
Which fat surgery reduces the size of the stomach?
Lap band surgery
What part of the SI is bypassed with gastric bypass surgery?
Duodenum
What happens during gastric sleeve surgery?
Removal of stomach but retain more of the pyloric stomach for gastrin release
