cgeorge's version from 2016-02-20 21:02


Question Answer
4 functions of stomach1) Store food 2) Mixes food with secretions 3) Regulates release of food > Duodenum 4) Secretes gastric juices
5 anatomical regions of the stomach (top to bottom) Cardia, fundus, corpus, antrum, pylorus
First part of the SIDuodenum
Physical adaptation of the antrumThick muscular wall
Mucous neck cells secreteMucous and bicarbonates
Parietal cells secretesAcid and intrinsic factor
ECL cells secreteHistamine
Chief cells secretePepsinogen and lipase
D cells secreteSomatostatin
G cells secreteGastrin
What substance binds to CCK8 receptors on parietal cellsGastrin
Predominant cells found in corpusParietal and chief (ECL/D cells are found though)
Predominant cells found in antrumG and D cells. NO parietal cells
Describe parietal cell stimulation1) H/K ATPase on apical membrane, pumps protons into lumen 2) K reenters cell via K recyling 3) Carbonic anhydrase provides H+/HCO3- 4)Cl/Bicarbonate exchanger on basolateral membrane exchanges Cl in, Bicarb out, Cl ions then leave cell via Cl chloride (apical memrbane) 5)Leaves HCl inn lumen
Why does interstitial space become basic?Bicarbonate ions cross basolateral membrane via Chloride/Bicarb exchanger
3 direct triggers of parietal cells?Ach, histamine, gastrin
2 indirect triggers of parietalThrough the ECL cells, Ach and gastrin can act on ECL cell to produce histamine
What hormone binds to H2 receptors on parietal cellsHistamine
Which hormones regulate acid secretion via PKC pathwayAch & Gastrin
Which hormone regulates acid via PKA pathwayHistamine
SST is a GPCR on parietal cells which somatostatin binds to
Effect of Somatostatin binding to SST receptor?Inhibits adenylyl cyclase, antagonises the stimualatory effect of histamine
D cells in corpus of stomach are triggered by Neural/Hormonal mechanisms
D cells in antrum of stomach triggered by Low PH
Somatostain released by D cells of coprus inhibitHistamine from ECL cells in corpus
Somatostatin released by D cells in antrum inhibitGastrin release from G cells in the antrum (decrease stimulation of ECL cells)
Distension of stomach causesAch release by the vagus nerve
Ach has 3 effects;1) Direct stimulation of parietal cells 2) Stimulate ECL cells to release histamine 3) Stimulate D cells in corpus to inhibit somatostatin release
Ach overall effect is toIncrease acid secretion
Vagal stimulation of G cells is via ... and its effect is Gastrin releasing peptide ... Triggers parietal cells directly and indirectly via ECL cell
Vagal stimulation of D cells is via ... and its effect is...Ach... Inhibit release of somatostatin
2 triggers to stimulate the D cells1) Low PH 2) Products of protein digesttion
Secretin is released by ... and its effect is...Duodenal S cells ... Inhibit antral gastrin release or cause somatostatin release
Duodenal S cells are stimualted byfat and acid
CCK is released by ...and produces its effect by ...Duodenal I cells... directly reduces parietal cell acid secretion
Duodenal I cells are stimulated by fat
Effect of prostaglandinsAct on parietal cells and inhibt HCl secretion
Effect of NSADSInhibit enzyme COX which make prostaglandins. = More acid secretion
4 phases of gastric acid secretionBasal, Cephalic, Gastric, Intestinal
Cephalic phase accounts for how much percent of total acid secretion 30%
Gastric phase accounts for how much of the total acid secretion50-60%
Main stimulant of the gastric phase Distension via vagovagal and local reflexes
Peptides also stimulateG cells to make gastrin
Vagovagal reflexes is made up ofGastrin releasing peptide activating gastrin cells and Achs 3 effects; 1) Acts directly on parietal cell 2) Act on ECL cells > Histamine 3) Act on D cells to inhibit release of somatostatin
Intestinal phase accounts for how much of total acid secretion?5-10%
How is the intestinal phase stimulated?Peptides/AA in SI stimulates acid secretion by activating duodenal G cells to secrete gastrin
Pepsinogens areProteolytic proenzymes
Conversion of pepsinogen > Pepsin occurs spontaneously at what PHPH<5
Role of pepsin?Its an endopeptidase, initiates protein digestion by cleaving other pepsinogens
Conversion of pepsinogen to pepsin is irreversible inactivated at what PH7.2
Prostaglandins are important inMaintaing the mucosa, they inhibit acid secretion and stimulate bicarb and mucous secretion
Adaptation of H.Pylori bacteria -Produces urease, converts urea > Ammonium and bicarb ions
H.pylori in corpus causesIL8 release from epithelial cell > Inflammatory response > IL1B by monocytes > IL1B is most potent acid suppressant