Drive - stomach Flashcards
What are the main functions of the stomach? (8)
Store and mix food
Dissolve and continue digestion
Regulate emptying into the duodenum
Kill microbes
Secrete intrinsic factor
Activate proteases
Lubrification
Mucosal protection
What are the 5 main types of cell found in the stomach?
Parietal cells,
Chief cells,
G cells
D cells
Enterochromaffin like cells (ECL)
What do parietal cells secrete?
HCl and intrinsic factor
What do chief cells secrete?
Pepsinogen
What do G cells secrete?
Gastrin
What do D cells secrete?
Somatostatin
What do Enterochromaffin like cells secrete?
Histamine
What is the function of gastrin?
Stimulate histamine secretion and stimulate HCl secretion
What is the function of ACh?
Stimulate histamine secretion and stimulate HCl secretion
What is the function of histamine?
Stimulate HCl secretion and increases in response to gastrin and HCl
What is the function of somatostatin?
Inhibit HCl secretion
What is the function of secretin?
Inhibit gastrin secretion
What is the function of CCK?
Inhibit HCl secretion
Promotes the flow of digestive enzymes from the pancreas and bile from the gallbladder
What is an ulcer?
A breach in the mucosal surface
What are the 4 main protective mechanisms of gastric mucosa?
Alkaline mucus
Tight junctions between damaged cells
Replacement of damaged cells (stem cell population)
Feedback loops
How is pepsin produced?
Pepsinogen is produced by chief cells and released into the stomach lumen. Upon contact with the low pH (acidic conditions) pepsinogen is converted to pepsin. (Then acts as a positive feed back loop as it aids the cleavage of pepsinogen to pepsin)
What is the empty stomach volume?
50ml
When eating (/just after) what can volume can the stomach accommodate?
1.5L
Where do peristaltic waves originate?
In the body of the stomach
What does the closing of the pyloric sphincter cause?
The majority of the food contents are forced back towards the body of the stomach meaning there is more mixing (and thus digestion)
What can cause an increase in the strength of contractions? (4)
Gastrin
Gastric distension
Decrease in sympathetic nervous system stimulation
Increase in parasympathetic nervous system stimulation
What can cause a decrease in the strength of contractions? (6)
Duodenal dissension
Increase in duodenal fat
Increase in duodenal osmolarity
Decrease in duodenal pH
Increase in sympathetic nervous system stimulation
Decrease in parasympathetic nervous system stimulation
