Gastric Secretion Flashcards
What are the three regions of the stomach?
Fundus
Body
Antrum
What are the functions of the funds?
Storage
What are the functions of the body?
Storage Mucus HCL Pepsinogen Intrinsic factor
What is the function of the antrum?
Mixing/Grinding and gastrin production
What is the function or mucus neck cells?
Mucus production
What is the function of chief cells?
Pepsinogen production
What is the function of parietal cells?
HCL production and Intrinsic factor production
What three mechanisms control gastric secretion?
Neurocrine, Endocrine and Paracrine
What aspects of neurocrine control are there?
Vagus and local reflexes
What stimulates the endocrine system in control of gastric secretion?
Gastrin (peptide hormone)
What molecule stimulates gastric secretion by the paracrine system?
Histamine
Increased vagal tone caused by sight, smell and taste of food activates what three stimulating pathways for gastric secretion?
Neurocrine (Ach) caused by distention of stomach (arrival of food)
- Endocrine (Gastrin) caused by peptides in lumen stimulate Parietal cells
Histamine produced from ECL cells also acts on parietal cells via a different pathway
What mechanisms inhibit gastric secretion?
Cephalic phase - (stopping eating) decreases vagal activity
Gastric Phase - (decreased pH) decreases gastrin secretion
Intestinal phase - (acid and fat in duodenum) enterogastric (splanchnic) reflex + secretin released fat causes GIP to be released - all decreases stimulation of parietal cells
What are enterogastrones?
Hormones released in the duodenal mucosa
What are the three examples of enterogastrones?
Secretin
Cholecystokinin
GIP
What are enterogastrones released in response to?
Acid
Hypertonic solution
Fatty acids/monoglycerides in duodenum
What is the collective effect of enterogastrones?
Prevent further build up of acid in the duodenum
What two strategies lead to inhibition of acid build up in duodenum?
Inhibit gastric secretion and reduce gastric emptying (inhibit motility/contract pyloric sphincter)
What is the inactive precursor to pepsinogen?
Zymogen
What cells secret pepsinogen?
Chief cells
What causes pepsinogen to convert to active pepsin?
Low pH (<3)
When is pepsin inactivate?
At neutral pH (7)
What are the mechanisms of pepsin control/secretion parallel to?
HCL secretion (parietal cell stimulation)
What is the only essential (non-compensated) role of the stomach?
Intrinsic factor production
