DIGESTION AND ABSORPTION OF CARBOHYDRATES AND PROTEINS Flashcards
(38 cards)
What can be found in saliva?
Water
Ions
Salivary amylase
Lysozymes
Where in the stomach would you find mucus cells?
Mostly in the cardiac and pyloric region
What’s the function of mucus cells?
They secrete mucous to protect the epithelium from acid secretions
Where would we mostly find parietal cells?
Mostly in the gastric region
What’s the function of parietal cells?
To secrete hydrochloride acid and intrinsic factor
Where would we mostly find chief cells in the stomach?
In the cardiac region
What’s the function of chief cells?
Secreting pepsinogen, the precursor of pepsin
Where in the stomach would we mostly find enteroendocrine cells?
In the gastric region
What’s the function of enteroendocrine cells?
They secrete protein hormones e.g. somatostatin
What volume of liquid can the stomach usually accommodate
2 litres
What initiates the cephalon stage?
Seeing, smelling or tasting food
What stimulates the salivary glands to secrete saliva?
The facial and glossopharyngeal nerves
Describe how peristaltic action in the stomach is initiated?
Food distends the stomach and stimulates stretch receptors in its walls. When receptors are activated, nerve impulses activate parasympathetic and enteric neurones which cause a wave of peristalsis.
Describe how the secretion of gastric juice occurs?
Chemoreceptors monitor the pH of the stomach chyme and when activates, nerve impulses activate the parasympathetic and enteric neurones which causes a secretion of gastric juice from gastric glands
What is chyme?
When food in the stomach mixes with gastric juice
Where is gastrin released from? What’s its function?
G cells of gastric glands
It stimulates gastric glands to secrete large amounts of gastric juice and strengthens the contraction of the lower oesophageal sphincter to prevent acid chyme reflux, it increases stomach motility and relaxes the pyloric sphincter = all of this increases gastric emptying
At what ph is gastrin inhibited?
Below pH 2
What is the intestinal phase of digestion?
When the chyme is found in the duodenum and the enterogastric reflex occurs
What’s the enterogastric reflex?
Inhibition of gastric motility and increased contraction of the pyloric sphincter to increase gastric emptying
What’s the function of cholecystokinin?
Stimulates secretion of pancreatic juice which causes contraction of the gall bladder to squeeze bile out and relax the sphincter of Oddi, slows gastric emptying by contracting pyloric sphincter and produces a feeling of fullness by acting on the hypothalamus, promotes normal growth/maintenance of the pancreas and enhances the effects of secretin
Where is secretin released from and what are the effects?
It’s released from S cells of the intestinal glands in the small intestine which stimulates the flow of pancreatic juices to buffer the acidic chyme and it inhibits the secretion of gastric juice
Where is histamine released from and how does it work?
Enterochromaffin like cells
They bind to H2 receptors on parietal cells and generate cAMP
How does gastrin act?
It binds to CCK2 receptors and activates phospholipase C which induces the release of Ca2+ into the cytoplasm
How does acetylcholine act on parietal cells?
It’s released from neurones and binds to M3 receptors which increases intracellular Ca2+ which helps the H+/K+ pump to work
