GI secretions: gastric, pancreatic and drugs for peptic ulcer disease Flashcards
What are the gastric secretory products?
HCl; intrinsic factor; pepsinogen; gastrin; mucus
What, where and stimulus of HCl secretion?
pareital cells;
body/fundus of stomach;
=>gastrin; ACh (from vagus); histamine
What, where and stimulus of intrinsic factor secretion?
pareital cells;
body/fundus of stomach;
=>gastrin; ACh (from vagus); histamine
What, where and stimulus of pepsinogen secretion?
chief cells;
body/fundus of stomach;
=> ACh (from vagus); gastrin; HCl
What, where and stimulus of gastrin secretion?
G cells;
Antrum;
=> small peptides/amino acids; vagus (via GRP); stomach distension
What, where and stimulus of mucus secretion?
mucous cells;
entire stomach;
ACh (from vagina)
inhibitors of HCl and intrinsic factor?
- Low pH inhibits (by inhibiting gastrin)
- prostaglandins
- chyme in duodenum (via GIP and secretin)
inhibitors of pepsinogen
H+ (via somatostatin)
inhibitors of gastrin
H+ (via somatostatin)
action of mucus
forms gel on mucosa to protect mucosa from HCl and pepsin;
traps HCO3 to helps neutralize acid
action of gastrin
- increase HCl secretion (parietal cells)
- increase pepsinogen secretion (chief cells)
- increase histamine secretion by ECL cells
action of pepsinogen
- Digests up to 20% of proteins
- converted to pepsin w/ low pH and pepsin (autocatalytic)
action of intrinsic factor
- necessary for VITAMIN B12 absorption by ileum;
- forms complex w/ vitamin B12
action of HCl
- kills pathogens
- activates pepsinogen to pepsin
What are the 3 primary triggers of H+ secretion?
- ACh (from vagus) => M3 muscarinic receptor
- Histamine => H2 histamine receptor
- Gastrin => unidentified receptor
Describe the 3 steps in gastric H+ secretion
1) parietal cell=> CO2, H2O converted to H+ and HCO3 via carbonic anhydrase
2) H+ secreted into lumen of stomach by H-K ATPase => Cl- is secreted w/ H+
3) HCO3 absorbed into bloodstream in exchange for Cl-
What is alkaline tide?
after meal=> enough H+ secreated to raise pH of systemic blood and turn urine alkaline => alkaline tide
3 phases of gastric secretion
cephalic, gastric, intestinal phases
how does cephalic phase of gastric secretion occur?
“senses” increase gastric secretion via PANS => 30% responsible for H+ secretion
how does gastric phase of gastric secretion occur?
-food in stomach increases secretion;
-proteins, peptides, alcohol, caffeine cause *gastrin release
-gastric distention initiates vagovagal reflexes
=>60% of acid secretion
how does intestinal phase of gastric secretion occur?
-protein digestion products in duodenum stimulate gastrin secretion;
-absorbed amino acids act to stimulate H+ by parietal cells
=>less than 10% of acid secretion due to meal
What are the drug classes for peptic ulcer disease?
antacids;
H2 antagonists; PPI;
mucosal protective agents; antibiotics
primary antacid agents
MgOH; AlOH; CaOH
What are the effects of antacids?
Mg=> laxative effect
AlOH=> constipating effect
