Littletone Part II Flashcards
The gastric mucosa is compased of two functional regions, what are they?
Oxyntic Gland Area (85%)
Pyloric Gland Area (15%)
What are the anatomic areas of the Oxyntic Gland Area?
Cardia
Fundus
Corpus
What are the anatomic areas of the pyloric gland area?
Antrum
Pylorus
Where do Ulcers tend to occur?
Near Mucosal Junction
Esophageal Junction
Oxyntic-Antral Junction
Gastroduodenal Junction
What causes Esophageal Ulcers?
Reflux disease. Gastric content is protruded twoard the lower esophageal spincter.
At the Cardia of the stomach there are specialized cells, what are they?
Cardiac Pacemaker cells
What is the function of cardiac pace maker cells?
Change stomach general motility when they become depolarized.
What is the main type ulcer that is usually found?
Gastric Ulcer
Duodenal Ulcers typicaly occur at which part of the duodenum?
head of the duodenum
Surface Mucous Neck Cells
Secrete
Mucous
Bicarbonate
trefoil peptidase (small, on surface of epithelial cell)
Stimulus for Release
Tonic Secretion ; with irritation of mucosa
Bicarb secreted with mucus
Function of Secretion (protection and lubrication)
Physical Barrier between lumen and epithelium
Bicarb buffers gastic acid to prevent damage to epithelium
Parietal Cells
Secrete
Gastric acid (HCL) - H+
Intrinsic factor
Stimulus
Ach, gastrin, histamine
Function of secretion
Activates pepsin, kills bacteria (protein digestion)
Complexes with vitamin B12 (cobalamin) to permit absorption of iron in ileum
Enterochromaffin-like cell
Secrete
Histamine
Stimulus
Ach, gastrin
Function of Secretion
stimulates gastric acid secretion
Chief Cells
Secrete
Pepsin(ogen)
Gastric Lipase
Stimulus
Ach acid, secretin
Function of Secretion (regulation of acid secretion)
Digest proteins
Digest fats
D cells
Secretes
Somatostatin
Stimulus
Acid in the Stomach
Functionof Secretion
Inhibits gastric acid secretion
G cells
Secretes
Gastrin
Stimulus
Ach, peptides, and amino acids
Function of Secretion
Stimulates gastric acid secretion
Endocrine Cells
Product
gastrin, histamine, somatostatin
Function
Regulation of acid secretion
Ionic concentrations in gastric juice vary with secretory rate. Describe how Cl-, H+, K+, HCO3-, and Na+ change and gastric secretion increases.
Cl- and H+ increase
K+ slight increase
HCO3- mild increase
Na+ huge decrease
This all happens as gastric secretion increases
Describe the Gastric Acid Secretion in the Parietal Cell
CO2 (readily acceptable to parietal cell) + H2O -> H2CO3 -> (carbonic anhydrase) -> HCO3- + H+
Hydrogen is removed out the cell by a H+/K+ Antiport, ATP (hydrogen excreted to lumen and potassium taken into the cell.
More Potassium also gets into the cell through the Na+/K+ ATP pump
Potassium needs to get back out. Sent out through positive charge potassium channel -> Lumen
Removal of Bicarb from the cell = Cl-/HCO3- exchanger (passive). Bicarb to plasma and Cl- taken into the cell. This Cl- is then sent to the Lumen through and negative charge chloride channel.
H+ + Cl- -> HCL in the lumen = increase in acidity
What is Electrogenic proton transport?
Coupling an electroneutral H+ for K+ ATP driven exchange activity (ATP) in parallel with conductive channels for K+ and Cl-, and eddicient recycling of K+.
The upper gastrointestinal mucosa is covered by a layer of what?
Mucus
What is mucus?
A viscoelastic get that contains 85& water and 15% glycoproteins.
It slightly impedes movement from the lumen to the apical cell membrane
(HCL flow sin HCO3 flows out
It is relatively impermeable to pepsin
A barrier to the diffusion of H+ and pepsin covers the gastroduodenal mucosa. What is it called?
Mucus-Bicarbonate Barrier
H+ flows in and HCO3 flows out
Lumen ph = 1-2
Mucosa ph = 7
While the luminal pH may be ______, the pH at the surface cell membrane is near _______.
acidic
neutral
During damage _______, _____, and other ________ _______ increase capillary filtration.
Histamine
Acid
Vasoactive Agents