Wk1 GI Phys Overview Flashcards
4 major layers of GI wall?
- Mucosa
- Submucosa
- Muscularis Externa
- Serosa
Three sub-layers of the GI mucosa:
- Epithelium
- Lamina propria
- Muscularis mucosae
Primary component of the GI sub-mucoa:
submucus nerve plexus
Three sub-layers of the GI muscularis externa:
- Circular muscle
- Myenteric nerve plexus
- Longitudinal muscle
Main difference between small intestine and colonic mucosa?
Small intestine has villi (increased surface area)
Colon is flat to lumen
Why such high rate of turnover in GI epithelial cells?
prevents accumulation of mutations due to toxin exposure
Organs with two layers of mucus:
stomach
colon
Organ with one layer of mucus:
small intestine
What protects protein core of mucus from proteases?
glycosylation
**carbohydrate side chains attract water to form gel
Exocrine digestive enzymes are secreted via?
zymogen granules
Zymogen docking and dumping stimulated by increase in which two substances?
cAMP
Ca2+
Small bowel overgrowth of bacteria causes increase in organic acid production and pulls water into lumen from the blood stream leading to:
osmotic diarrhea
Infection causing an excess secretion of chloride drawing water into the lumen causes?
secretory diarrhea
antidiarrheal that slow transit time leading to increased fluid absorption:
loperamide
Average transit time of the esophagus:
10 sec
Average transit time of the stomach:
4-5 hours
Average transit time of the small intestine:
2.5-3 hours
Average transit time of the colon:
30-40 hours
Biochemical characteristic of smooth muscle sphincters:
maintain tone without increase in intracellular Ca2+
Slow wave electrical activity of SM cells initiated by?
interstitial cells of Cajal
Increased AP generation of SM cells caused by increased?
amplitude
NOT frequency
Review SM contraction on slide…
37
NT released by enterochromaffin cells?
serotonin
role of serotonin in the gut?
afferent gut sensation
Excitatory NT’s of the enteric nervous system:
Ach
neurokinin A
substance P
Inhibitory NT’s of the enteric nervous system:q
vasoactive intestinal peptide
NO
Review slides…
45 and 46
NT’s that generally decrease GI SM contractility:
norepinephrine
dopamine
neuropeptide Y
(Sympathetics….fight or flight)
NT’s that generally increase GI SM contractility:
Ach
parasympathetics….rest and digest
Primary excitatory NT from sensory cells and motoneurons to muscle, epithelium, secretory cells and interneuronal junctions; increases intracellular Ca2+:
Acetylcholine
released from vagal nerve endings to stimulate G cell secretion of gastrin:
Gastrin releasing peptide
an excitatory transmitter generally co-released with acetylcholine:
substance P
promotes motility
relaxes smooth muscle in esophagus and stomach
stimulates fluid secretion and promotes dilation of GI vasculature
increases cAMP
Vasoactive Intestinal Peptide (VIP)
an inhibitory transmitter co-release with VIP from inhibitory motoneurons
hydrophobic
intracellular targets
NO
transmitter review table on slide…
51
G cells in antrum of stomach detect amino acids leading to pepsinogen and H+ release by parietal cells:
Gastrin
I cells in duodenum/jejunum detect fat and amino acids, secretion of pancreatic enzymes and bile salts involved in fat uptake:
Cholecystokinin (CCK)
S cell primarily in duodenum/jejunum detect acid stimulates secretion of pancreatic juice including BICARB and inhibits gastric motility:
Secretin
K cells in D/J detect carbs and fat to inhibit gastric acid and stimulate insulin release from pancreas:
GIP
gastric inhibitory peptide or glucose dependent insulinotropic peptide
secreted by endocrine cells; released cyclically during fasting state to initiate Migrating Motor Complex
Motilin
Paracrine regulator from ECL cells:
histamine
Paracrine regulator from D cells:
somatostatin
Vocab word: burping?
eructation
Vocab word: rumbling noise created by movement of gas in bowels?
borborygmi
