Case 3 - The pancreas Flashcards
What if the function of B5, B6 transporters
- B5 - involved in calcium absorption in the kidney
- B6 - involved in calcium absorption in the small intestine
What are the end products of polysaccharide digestion and where does it occur?
- Polysaccharides are digested to:
- Monosaccharides
- Occurs in:
- Saliva
- pancreas
- brush border
What causes pathological secretion of ions by the gut
- Caused by E.coli and rotavirus
- toxins produced by bacteria hijack nromal celullar processes
- intestinal cells normally secrete H2O together with mucus and HCO3- (2L per day)
- In cholera secretion exceeds 20 L per day
- Some toxins also inhibit sodium absorption but not SGLT1 (oral rehydration therapy)
What are the water soluble vitamins
- B group
- C
What are the mechanical causes of acute pancreatitis?
- Gall stones
- trauma
- latrogenic injury
- operative injury
- endoscopic procedures with dye injection
Explan how cholesterol is absorbed?
- Occurs in the duodenum
- receptor mediated endocytosis
- Ezetimibe inhibits endocytosis = decreases plasma cholesterol
- Nieman - Pick Cl-like (NPCIL1) PROTEIN
What ar ethe effects of alcohol abuse in the mouth/upper GI?
- Increase incidence of cancer especially
- tongue
- buccal mucosa
- gums
- pharynx
- upper oesophagus (cigarrettes and spirits)
How is iron absorbed into the cell?
- Iron is transported through the DMT as ferrous (reduced form) Fe2+ at the same time as it transports protons (secondary active transport) leading to the accumulation of ferrous ions
- Iron is absorbed as haem protein, haem is oxidised releasing iron in the form of ferric ions Fe2+which are reduced to ferrous ions, the remainder of the haem protein forms biliverdin a precursor of bilirubin
What does a decrease in SI surface area such as in Crohns or Coeliac lead to
- Malabsorption
How does CCK control pancreatic secretion?
- Stimulates secretion of enzyme component
- produced by APUD cells in the duodenal mucosa in response to food constituents in the duodenal chyme
- CCK and gastrin compete for the same receptors on acinar cells
- CCK, gastrin and Ach all increase enzyme protein synthesis and secretion via increasing intracellular calcium and increase in phosphatidylinositol turnover
How is calcium absorped?
- Calcium absorption can be paracellular or intracellular down a concentration gradient
Transcellular route
- Calcium enters the cell via the apical using a channel TRPV6
- In the cell cytoplasm it binds to the protein calbindin to prevent calcium acting as an intracellular signal
- at the basolateral membrane calcium is removed by a calcium pump Ca2+ - ATPase in exchange for H+ antiporter
Paracellular route
- Ca2+ travels down a concentration gradient through the tight functions of the cells
What is absorbed in the ileum?
- Vitamin B12
- Bile salts
- Potassium
Explain the pathogenesisi of defective intracellular transport of proenzymes within acinar cells.
- In normal acinar cells, digestive enzymes and lysosomal hydrolases are transported in separate pathways
- In acinar injury they are transported to the same place leading to activation of proenzymes
What are the end products of protein digestion and where does it occur?
- Proteins are digested to
- Amino acids
- dipeptides
- tripeptides
- Occurs in the:
- stomach
- pancreas
- bursh border
What is chronic pancreatitis?
- Prolonged inflammation of the pancreas,
- irreversible destruction of exocrine parenchyma,
- fibrosis in the later stages
- destruction of endocrine parencyma
What are the mechanisms to preventthe pancreas from autodigestion from its own enzyme?
- Enzymes secreted by the pancreas are inactive proenzymes packaged in zymogens which are secretory granules
- The packaged proenzymes are activated by trypsin which is activated by duodenal enteropeptidase in the SI therefore intrapancreatic activation of proenzymes is minimal
- acinar and ductal cells secrete trypsin inhibitors e.g. serine protease inhibitor Kazal type I (SPINKI) which limit intrapancreatic trypsina activity
Explain how short chain fatty acids?
give examples of SCFA
- Butyrate, propionate, acetate
- SCFA are not a major component of the diet, but produced by bacterial fermentaion in the colon
Explain how amino acids are absorbed from the lumen to isf.
- 50% are absorbed by the co-transporter (symporter) Pep T1 as di and tripeptides with H+
- Hydrolysed to amino acids in enterocytes
- absorbed via secondary active transporter
How are triacyglcerides resynthesised?
- Resynthesised in SER and packaged in chylomicrons
- exocytosis of chylomicrons which are then transported in lymphatic to the liver
Which pancreatic enzymes are released as enzyme precursors?
- Trypsin
- Chymotrypsin
- Carboxypeptidase
- Elastase
- Phospholipase A
What are the effects of alcohol abuse in the pancreas
acute and chronic pancreatitis
How does alcohol consumption lead to acute pancreatitis?
- Alcohol activates all the methods that cause acute pancreatitis
- it increases contraction of the sphincter of Oddi
- Chronic consumption leads to production of protein rich pancreatic fluid causing obstruction of small pancreatic ducts
- Leads to alcohol induced oxidative stress which may promote the fusion of zymogens and lysosomes and alter intracellular calcium levels due to mitochondrial damage
Name all the fat soluble vitamines
- A
- D
- E
- K
What are the common causes of pancreatic obstruction?
- Gallstones
- biliary sludge
- periampullary neoplasms
- choledochoceles
How does somatostatin control pancreatic secretion?
- Inhibits
- pancreatic secretion
- release of exocrine enzyme
- alkaline secretion
- insulin
- glucagon
- CCK
- secretin
- gastrin
- Release from D cells in iselts is stimulated by gastrin, cck, secretin release