Gastric Secretion Flashcards
What are the 3 main areas of the stomach?
Fundus
Body
Antrum
What 2 areas of the stomach are used for storage?
Fundus
Body
What 4 substances does the body of the stomach secrete?
Mucus
HCl
Pepsinogen
Intrinsic factor
What are the 2 functions of the antrum?
Mixing/grinding
Secretion of gastrin (hormone)
What is the dipped area before a gastric gland called?
Gastric pit
What are the 3 types of cell (from gastric pit descending) found in the gastric gland?
Mucous neck cells
Chief cells
Parietal cells
What substances do the following cells secrete:
a) Mucous neck cells
(b) Chief cells
(c) HCl (2
(a) mucus
(b) pepsinogens
(c) HCl & intrinsic factor
What cells secrete gastrin?
G cells
What are the 3 main mechanisms of control for gastric acid secretion and how are they regulated?
Neurocrine (vagus/enteric reflexes
Endocrine (gastrin)
Paracrine (histamine)
What is the stimulus for the vagal/enteric reflexes to release ACh
Distension of stomach (the arrival of food)
What is the stimulus for the G cells to release gastrin?
Peptides in the lumen
What are the stimuli (2) for the ECL cells to release histamine?
Gastrin
ACh
What are the 3 phases of gastric acid secretion?
Cephalic phase
Gastric phase
Intestinal phase
How can gastric secretion be inhibited in the cephalic phase and why?
By stopping eating - Decreases vagal activity
How can gastric secretion be inhibited in the gastric phase and why?
By decreasing the pH (and therefore increasing HCl) - Decreases gastrin secretion
What are enterogastrones?
Hormones secreted by gland cells in the duodenal mucosa
Give 3 examples of enterogastrones?
Secretin
Cholecystokinin (CCK)
Gastric inhibitory polypeptide (GIP)
The presence of what 4 substances in the duodenum would cause enterogastrones to be released?
Acid
Hypertonic solutions
Fatty acids
Monoglycerides
What is the collective function of all enterogastrones?
To prevent further acid build-up in the duodenum
What 2 methods are used by enterogastrones to prevent further acid build up in the duodenum?
Inhibit gastric acid secretion
Reduce gastric emptying (by inhibiting the motility of the pyloric sphincter)
What is pepsinogen an inactive precursor for?
Pepsin
What is a zymogen?
An inactive precursor of an enzyme?
Why is zymogen storage important?
Prevents cellular digestion
How is pepsinogen activated?
When released into a low pH (>3)
When is pepsin inactivated?
At a neutral pH (7)
What type of role does gastric mucus have?
A Cytoprotective Role
What are the 2 functions of gastric mucus?
Protect mucosal surface from mechanical injury
Protect agains gastric acid corrosion and pepsin digestion (via neutral pH HCO3)
What is intrinsic required for?
Vitamin B12 absorption to form complex
Where is the intrinsic factor/B12 complex absorbed from?
The ileum
What condition can a lack of intrinsic factor lead to?
Pernicious anaemia
