Digestion and absorption of foodstuffs Flashcards
What cells in the pancreas secrete things and what do they secrete
Acinar cells release non-active enzymes
What do duct cells release from the pancreas and what does this mean
Bicarbonate ions so the pancreas releases and aqueous alkaline secretion
How is the HCO3-/Cl- exchange affected in cystic fibrosis sufferers
Cl- ion channel is absent in cystic fibrosis which can cause malabsorption in CF sufferers
What is the function of the bicarbonate ions
Neutralise acid chyme which is necessary for:
- Digestive enzyme activity
- Micelle formation (fat absorption)
- Protecting duodenal mucosa
What is needed for disaccharides to get turned into monosaccharides
Sodium because it is a sodium dependent process (and therefore energy dependent)
How are disaccharides turned into monosaccharides
Sodium is driven out of cells in the epithelial cells of the villus into the capillaries. This creates a conc gradient
Therefore the sodium in the brush border is driven through co transport carriers into the cells. As it does this, the disaccharides come into contact with the disaccharidases. Therefore it aids the absorption of the newly formed monosaccharides into the epithelial cells
Why are enzymes from the pancreas released in a non active form
Because they would have an auto digestive function if they did
What are peptidases activated by
action of trypsin
How does absorption of amino acids and di and tri-peptides occur
By passive diffusion or facilitated transport
How are di and tri-peptides broken down into amino acids
BY intracellular peptidases
What does emulsification involve and where is this derived from
Bile acids- from liver and released from stores in the gall bladder
What is formed from the action of pancreatic lipase and how are they absorbed
Monoglycerides and free fatty acids (and some glycerol)
-They’re not water soluble so absorbed by forming a micelles
How are fats reformed in the cell and how are they then transported to the rest of the body
Intracellular reformation of triglycerides
-They combine with phospholipids, cholesterol and protein to form a chylomicron and then are transported via the lymphatic system
What controls pancreatic secretions
Vagus nerve
Conditioned stimuli (cephalic phase)
Presence of food in the stomach (gastric phase)
How does Ach help control pancreatic secretions
It potentiates the actions of secretin and cholecystokinin
secretin- released in response to acid in duodenum and stimulates bicarbonate production
Cholecystokinin- stimulates enzyme rich secretion. It is released in response to presence of fat and protein in duodenum
