Secretions of the Stomach and Pancreas

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Mucous
Secreted by surface goblet cells and mucous neck cells - it neutralises acid in the lining of the stomach to prevent corrosion to the stomach wall by gastric acid
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Acid
Secreted by parietal cells - it allows for a sterile environment; it produces pepsinogen which is converted to pepsin to allow for the partial digestion of proteins before they go to the small intestine; it converts Fe3+ to Fe2+ for easier absorption
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Histamine
Secreted by enterochromaffin-like cells - stimulates acid secretion from parietal cells
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Gastrin
Secreted by G cells - it stimulates the acid secretion from parietal cells and histamine secretion from ECL cells.
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Somatostatin
Secreted by D cells - it inhibits acid secretion from parietal cells
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Pepsinogen
Secreted by chief cells (zymogen) - starts protein digestion in the stomach
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Intrinsic factor
Secreted by parietal cells - helps to absorb vitamin B12 from the ileum more easily. Vit B12 is essential for the maturation of RBC. You can otherwise end up with premicious anaemia
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Acid secretion
Acid secretion only occurs whilst we're eating, otherwise parietal cells are in inactive form. When there is stimulation, its tubulovesicles merge together to produce canaliculi which increases their surface area, ready for acid secretion
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Endocrine
A stimuli of parietal cells - Gastrin hormone is released from the stomach into the bloodstream; it eventually goes back to act on the parietal cells, this causes a greater effect
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Paracrine
A stimuli of parietal cells - Histamine is released from the stomach's ECL cells to act on nearby parietal cells
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Neurocine
A stimuli of parietal cells - The vagus nerve can release the neurotransmitter acetylcholine to signal to the parietal cells to produce acid
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Cephalic
First phase of acid secretion - a neural phase. The thought/sight/smell of food leads to ACh release from the vagus nerve to bind to receptors on parietal cells, causing acid secretion. Indirectly, it stimulates histamine and gastrin release
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Gastric
Second phase of acid secretion. Food enters the stomach, causing stretching/distension which is detected by pressure receptors. This causes ACh release. The breakdown of proteins into peptides and amino acids stimulate gastrin release
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Intestinal
Third phase of acid secretion - an inhibitory phase. After chyme is passed into the small intestine and the stomach is empty, acid secretion must be inhibited. Presence of food stimulates CCK release and presence of acid stimulates secretin release
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CCK
Stimulates the production of digestive enzymes in the pancreas. Also acts on parietal cells to inhibit acid secretion. Stimulates the gallbladder to release bile which emulsifies fats
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Secretin
Stimulates the production of HCO3- in the pancreas. Also acts on the parietal cells to inhibit acid secretion
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Alkaline tide
The presence of large amounts of HCO3- in the bloodstream after eating means that (theoretically) it would completely neutralise the acid and remain in excess, rendering the blood alkaline. However, this is counteracted.
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Peptic ulcer
A lesion in the mucosa of the digestive tract. If it is in the stomach = gastric ulcer, if it is in duodenum = duodenal ulcer. Nearly all that are not associated with NSAIDs are caused by H pylori bacteria
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Pancreas
An organ that lies behind the stomach; has a head, body and tail arrangement; and has both endocrine and exocrine functions
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Digestive enzymes
Proteases, lipases, carbohydrases, nucleases
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Trypsinogen
A protease enzyme that enters the small intestine and is converted to its active form by enterokinase. It can then activate other inactive zymogens
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Chymotrypsinogen
Active form = chymotrypsin
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Pro-elastase
Active form = elastase
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Pro-carboxypeptidase
Active form = carboxypeptidase
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Pro-phospholipase A
Active form = phospholipase A
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PGE2
This signalling molecule is released from arachidonic acid. It inhibits gastric acid secretion and increases HCO3- production and the mucosal layer. NSAIDs block the COX enzyme, preventing the production of this molecule, leading to ulcers
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Card 2

Front

Secreted by parietal cells - it allows for a sterile environment; it produces pepsinogen which is converted to pepsin to allow for the partial digestion of proteins before they go to the small intestine; it converts Fe3+ to Fe2+ for easier absorption

Back

Acid

Card 3

Front

Secreted by enterochromaffin-like cells - stimulates acid secretion from parietal cells

Back

Preview of the back of card 3

Card 4

Front

Secreted by G cells - it stimulates the acid secretion from parietal cells and histamine secretion from ECL cells.

Back

Preview of the back of card 4

Card 5

Front

Secreted by D cells - it inhibits acid secretion from parietal cells

Back

Preview of the back of card 5
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