Gastric Secretions

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  • Created by: Becca
  • Created on: 23-12-13 22:03
What are the 2 secreting regions of the stomach & where are they?
Oxyntic mucosa in the fundus & body. Pyloric gland area in the antrum. Mucosal gland cells are found in gastric pits.
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What are the 4 cell types in the stomach & what do they produce?
Parietal cells: HCL, intrinsic factor that binds vitamin B12 to enable its absorption. Surface epithelia: mucous. Mucous neck cells: mucous. Chief cells: pepsinogen
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HCl does not digest material. How does aid digestion?
Activation of pepsin, provides an acid medium for optimal pepsin activity, aids the breakdown of connective tissue & muscle fibres
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What is the major digestive constituent of gastric secretions?
Pepsinogen produced by chief cells
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What are the 3 phases of gastric secretion?
Cephalic, gastric & intestinal phases
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Describe the cephalic phase of gastric secretion
Secretion stimulated (thought/expectation/sight/taste/chewing/swallowing) prior to food, contributes 30-50% secretions, dependent on activity of the vagus nerve (CNS involved)
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Describe the gastric phase of gastric secretion
50-60% secretions, local vago-vagal reflexes in response to mechanical stimulation due to food in antrum (no CNS involved), stimulation of gastric release from G-cells by peptide fragments of partially digested proteins (major mechanism)
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Describe the intestinal phase of gastric secretion
5% maybe due to circulating amino acids or gastrin
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What are the mechanisms of gastric circulation?
Local metabolite production (prostaglandins maintain capillary network, provide enough fluid for secretions), release of vasoactive intestinal polypeptide (VIP) from local nerves causing vasodilatation
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How is gastric secretion inhibited?
Removal of peptide fragments (no longer stimulates gastrin release). Removing food decreasing pH, pH
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How is gastric mucosa protected from gastric secretions?
Luminal membranes are impermeable to H+, -ve feedback: pH
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Card 2

Front

What are the 4 cell types in the stomach & what do they produce?

Back

Parietal cells: HCL, intrinsic factor that binds vitamin B12 to enable its absorption. Surface epithelia: mucous. Mucous neck cells: mucous. Chief cells: pepsinogen

Card 3

Front

HCl does not digest material. How does aid digestion?

Back

Preview of the front of card 3

Card 4

Front

What is the major digestive constituent of gastric secretions?

Back

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Card 5

Front

What are the 3 phases of gastric secretion?

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