Monogastric pt 5 Flashcards
What are the cells in the gastric glands?
- Surface epithelial cells
- Mucous neck cells
- Parietal
- Stem
- Chief
- Endocrine cells
What do surface epithelial cells do?
Secrete mucous and HCO3 protective function
What do mucous neck cells do?
Secrete thin mucous, cell division
What do parietal cells do?
HCl secretion, intrinsic factor secretion for vitamin B12 absorption
What do chief cells do?
Pepsinogen secretion
What do endocrine cells do?
Secrete regulatory substances (somatostatin, gastrin, histamine)
What are the glands in the cardia?
- Secrete only mucous
- Alkaline
- Protective function
What are in the glands in the antrum?
No parietal
- D cells (somatostatin)
- G cells (gastrin)
- Chief cells
What kind of secretion is HCl?
Isotonic for protective and protein denaturation and optimization of pH for proteolysis
How is H extrused?
Through H/K ATPase where K is recycled
How is HCO3 reabsorbed?
Not significant if healthy through and can cause an alkaline tide
What blocks the H/K ATPase blocker?
Omeprazole
What causes gastrin secretion and what is the source?
G cells and ACh
What causes histamine secretion and what is the source?
ECL, mast cells; gastrin, ACh
What causes ACh secreted and what is the source?
Vagus, ENS
What do Gastrin, histamine, and Ach stimulate?
H/K ATPase on the luminal side
What inhibits the H2 receptor (histamine receptor)?
Ranitidine, cimetidine
Aren’t as effective as omeprazol
What does somatostatin do?
Inhibit histamine stimulated HCl secretion. Either by blocking the release of histamine from parietal cells or by inhibiting adenylate cyclase.
Inhibit HCl through G cell release
What is pepsinogen?
Zymogen that is released and cleaved and activated by low pH to make pepsin, positive feedback where pepsin cuts up more pepsinogen
What activates pepsinogen release?
- ACh
- Peptide hormones
- Beta adrenergic component
What happens when luminal pH gets too low?
Gastrin secretion ceases so less pepsinogen and HCl
What are the phases of gastric acid secretion?
- Basal-no secretion
- Cephalic-30% acid secretion
- Gastric-Most acid secretion
- Intestinal
What happens during the cephalic phase?
Vagal input causes ACh release which binds to parietal cells and causes gastrin release
What happens during the gastric phase?
Presence of food in the stomach causes distension sensed by stretch receptors and ACh gets secreted. This stimulates G cells (low pH eventually turns these off) and Parietal cells and you get HCl secretion
What buffers the pH of the lumen?
Food in the lumen. This relieves inhibition of G cells by low pH and sustains gastrin and HCl secretion
What is the effect of NSAIDs on HCl?
This blocks COX1 and 2 which lowers PGE secretion. This causes an increase in parietal cell acid secretion
What are the exocrine pancreas secretions?
- Digestive enzymes
- Electrolytes
- HCO3
What are the secretions of the liver?
- Bile
- Electrolytes (HCO3)
What type of enzymes are released from acinar cells?
Zymogens that get released into duodenal lumen and activated after cleavage
What type of enzymes released from pancreatic acinar cells are there?
- Lipid breakdown
- Nucleic acid breakdown
- Protein breakdown
What is the pH of pancreatic juice and why is it important?
High 8.1 due to HCO3 concentration; Neutralizes luminal acidity and is optimal for enzyme function and micellar solubilization
What regulates HCO3 secretion?
-ACH
-CCK
-Secretin
-VIP
All stimulate the acinus. ACh and secretin stimulate the duct
What is the primary hormone for acinar secretion?
CCK
What is the main hormone for ductal secretion?
Secretin
What makes up the epithelial cells of the liver?
Hepatocytes
What is the origin of bile?
Cholesterol (nonsoluble) with bile acids (partially soluble)
What is the purpose of bile?
Emulsification of dietary lipids
Where is bile stored?
Gallbladder
When are bile acids released?
When sphincter of Oddi opens when food is in the lumen and CCK regulation. Released into the duodenum and reabsorbed in the ileum where it recirculates to the liver through the portal vein
What happens in species that do not have a gallbladder?
Bile is continuously released (horse, rat)
