Gastric Motility and Secretions Flashcards
Storage and receptive relxation
Storage - very distensible….diffuse organization of actin and myosin filaments, stress and receptive relaxation
Recp - PNS mediated reflex that occurs upon swallowing to cause relxation of gastric smooth muscle and a dec in pressure BEFORE food enters the stomach
Antralpyloric systole
During feeding, slow waves inc in aplitude and start to causes APs
Rhythm is slightly inc by gastrin and dec by secretin
Amplitude of slow wave is markeldy affected by gastrin, secretin, others
Gastric emptying
Rate is slowed by small volume, high osmotic pressure, and high fat or protein content
Greater stomach volume leads to inc rate of emptying
Greater energy density will slow rate of empyting
Gastrin HCl Pepsinogen Preduodenal lipases IF Ionic comp
G cells
Sterilizes chyme and helps to solubilize Fe (from parietal cells)
Inactive protease
Binds to B12 - from pareital cells
At low rates, gastric jujice is hypotonic and low acid conc…at higher rates becomes more isotonic and pH is lowered…K is always higher than plasma
Acid production mechanism
Na/K ATPase and HCO3/Cl on basal membrane
On apical - H/K ATPase
Structural change involved in secretion
Secretoary are blind vesilces at rest but once stimulated, canaliculi fuse to make long canaliculi which open
Signals affecting H secretion by parietal cells
Gastrin, histamine, and Ach all pos
Somatostatin neg
HCl production
Histamine potentiates Ach and gastrin effects
Ach - M3 - Ca
Histaine - H2 - cAMP - H+
Gastin - gastrin- Ca
Chief cell-parietal cell interplay
Chief cells secrete pepsinogen…cleaved to pepsin by H+…cleaves protein to peptides
Negative feedback during gastrin phase
D cells stimulate somatostatin at pH of 1 which is paracrine inhibition of gastrin
Digestion and absorption in stomach
Carb digestion by salivary amylase inactivated in stomach
Limited absorption - alcohol and aspirin
peptic ulcer
Zollinger-ellison
Helicobacter
Acute gastritis
Erosions of mucous membranes or duodenum produced by action of HCl
Ulcers of duodenum produced by excessive gastric acid secretions
Bacterium that resides in GI tract that may produce ulcers
HIstamine released by tissue damage and inflammation stimulates more acid secretion
Protective mechs of stomach
Parietal cells and cheif cells impermeable to HCL
Alkaline ucus
Tight jxns
Rapid cell division
PGs inhiibt gastric secretions
Peptic ulcers and gastric mucosal barrier
Erosions of mucosa of stomach or duodenum extending into muscularis externa…produced by action of HCl, refluxed bile salts or ingested substances
Natural protective mechansi
