GI Phys Gastric Secretion Flashcards
What are the five secretory products of the stomach
- Hydrogen Ion- This activates the conversion of Pepsinogen into Pepsin
- Pepsinogens- Released by chief cells, chiefs fans have pep remember, gets converted to pepsin which helps digest proteins
- Mucus- Lubricates food, released by mucus cells
- Intrinsic factor- necessary for vit B12 absorption
- Water- Dissolves and dilutes ingested material
Where is the oxyntic gland mucosa of the stomach located?
Located throughout the fundus and the body of the stomach
Where is the pyloric gland mucosa of the stomach located?
Located throughout the antrum of the stomach
What cell types are present in the oxyntic gland mucosa and what is released?
Parietal cells- HCL and IF
Chief Cells- Pepsin
What cell types are present in the pyloric gland area?
G cells- Gastrin
Mucus cells- mucus
D cells- somatostatin
In regards to the gastric gland, what cell types lie near the top of the gland?
mucous cells
Chief cells are located where in the gastric gland?
Near the bottom
What are the stem cells of the gastric gland?
Mucous neck cells,
Mechanism of acid secretion…kno
SLIDE 5
What is the potential difference across the cell membranes of the mucosa in the esophagus?
-15
What is the potential difference across the cell membranes of the mucosa in the stomach
-60 - -80
Aspirin and Ethanol do what to the potential difference?
Decrease it by disrupting cell membranes and leading to the separation of charges across the mucosa
The concentration of what ions in gastric juice vary with the rate of secretion?
As secretion goes up, more Hydrogen ions are secreted and less Na is secreted
The three major stimulants of gastric acid secretion?
Ach, Gastrin, Histamine
Yes, Gatrin can stimulate the generation of H+ by itself, but what is its most important Acid generating function?
It stimulates the release of Histamine from Enterochromaffin-like cells
Gastrin and Ach generate H+ secretion by raising levels of what inside the cell?
Ca2+ and IP3
Histoamine raises levels of H+ secretion by doing what>
raising cAMP levels inside the cell
The more you enjoy a meal, the more acid is secreted
ok
What is the cephalic phase of acid secretion
WHen smell, taste, chewing, swallowing, and hypoglycemia trigger vagus nerve signals to stimulate acid release from the parietal cells and gastrin release from the G cells.
KNOW….Gastrin is release from G cells into the bloodstream, it does not go straight to the parietal cells but rather travels through the liver and into the heart before being pumped out and sent to through the blood to the stomach.
ok
Gastric phase of acid secretion
Distension and food in the stomach triggers acid secretion via Ach short and long reflex
What is the stimulus for somatostatin release from D cells?
pH drops below 3
Does somatostatin inhibit gastrin release directly?
yes…also directly inhibits acid secretion
Secretin does what
Inhibts gastrin and acid
WHat is the stimulus for Secretin release and where do the S cells lie?
Any acid stimulates secretin release since S cells are located in the duodenum
What does GIP do?
Inhibits gastrin and acid….there is a good chart for all these mechanisms on slide 22
Where are the K cells (GIP releasers) located and what stimulates GIP release?
Fatty acids stimulate GIP release
4 ways that cells are set up to secrete acid
1) H/K ATPase
2) Carbonic anhydrase
3) Tubulovesicles
4) Negtive interior of cell
Chronic vomitting
Metabolic alkalosis because you lose H+ (gastric acid)
Chronic diarrhea
Metabolic acidosis…now you are losing mostly bicarbonate
In teh stimulated stomach, does the oxyntic or non-oxyntic secretion predominate
oxyntic
The cephalic phase of acid secretion is stimulated by
The vagus nerve
