Pancreas And GI tract Physiology Flashcards
(22 cards)
What is the GI tract?
Smooth muscle under involuntary control, except striated voluntary muscle at the upper oesophagus and anus, spans from the mouth to the anus. Major organs are stomach, pancreas, gall bladder, small intestine and large intestine
What is peristalsis?
Symmetrical contraction and relaxation of smooth muscles that propagates in a wave down a tube
What types of absorption happen in the intestines?
95% small nutrient absorption in small intestine
Large intestine : absorption of fluid
How is the GI tract regulated?
Parasympathetic nervous system: Vaal nerve stimulation and release of ACh
Intrinsic nervous system: stretch receptors in oesophagus, stomach and intestine
Hormones: released as a result of above acting nearby, paracrine, and far away tissues, endocrine l
What are the three stages of digestion and absorption?
Neurogenic phase: stimulated by sight, smell and taste. Stimulates parasympathetic nervous system, vagal nerve and ACh
Gastric phase: stimulated by distension of stomach, HCl release from stimulation of parietal cells by vagal nerve, amino acids and peptides in stomach. Causes release of gastric
Intestinal phase: stimulated by peptides and fatty acids in duodenum and a pH < 4.5. Causes release of CCK and secretin
What are the main functions of the stomach?
Mechanical breakdown of food
Release of gastric acid from parietal cells
Release of intrinsic factor for B12 absorption
Release of pepsinogen from chief cells
Release of gastrin from G cells
What are the actions of gastrin?
Stimulate: gastric acid release, secretion of pancreatic juices, secretion of pepsinogen and secretion of somatostatin
What are the three sections of the small intestine?
Duodenum, jejunum and ileum
What are the functions of the pancreas?
Endocrine: secretes insulin, glucagon and somatostatin
Exocrine: secretes pancreatic juice: fluid, bicarbonate, electrolytes and enzymes
Why are bile acids needed?
To emulsify non-water soluble fats (triglycerides, cholesterol, fat-soluble vitamins)
What happens following emulsification?
Lipase and cholesterol ester are from pancreas can digest them. Micelles form and then diffuse across the phospholipid membrane of the brush border enterocyte cells. Made into chylomicrons and enter lymph system and then liver.
What are the symptoms of malabsorption?
Diarrhoea, statorrhea, malnutrition, abdominal pain, abdominal distension
What tests would be used to confirm malabsorption?
Biochem: U&E, calcium and albumin and Mg+
Heam: FBC, Folate, vit B12, iron, ferritin, prothrombin time
What are the investigations of gastric function?
H. pylori in peptic ulcer disease
Fasting gastrin in Zollinger-Ellison syndrome
What investigations could be used for intestinal function?
TTG antibodies and then endomysial antibodies if positive
Hydrogen breath test - lactose intolerance
Markers of inflammation - CRP/ESR (non-specific) or faecal calprotectin (specific)
What is faecel calprotectin?
Calcium binding protein present in neutrophils
Excerpted into lumen during intestinal inflammation
Differentiate function disease (IBS) from organic disease (IBD)
Raised in GI malignancy, infection, gastric ulcers, esophagitis, diverticulitis and use of NSAIDs
What are the pancreatic function tests?
No ideal test exist
Invasive: specific, sensitive but unpleasant, time consuming and rarely used
Non-invasive: not as specific for pancreas, not as sensitive, but quick, easy and cheap. Used routinely
How do the invasive pancreatic function tests work?
Stimulate pancreatic secretion of enzymes, bicarbonate and fluid using lundh test meal or CCK and/or secretin. Collect directly from pancreas using endoscope, measure volume and enzyme activity.
How do the non-invasive pancreatic function tests work?
Three types:
1) measure undirected food in stool or breath
2) measure pancreatic enzymes in stool or blood
3) measure synthetic compound in urine, stool or breath that is hydrolysed by pancreatic enzymes (NBT-PABA test or pancreolauryl test)
What are breath tests?
Good for disaccharide insuffiency or intestinal bacterial overgrowth
Sugars not digested and absorbed instead are fermented by bacteria in large intestine to produce methane and/or hydrogen
Give glucose/lactose for bacterial overgrowth
Give fructose, lactose for disaccharide insufficiency
What is the faecel elastase test?
Elastase-1 is protease secreted by pancreas into the lumen, resistant to digestion by other enzymes so is excertes in faeces.
>200μg/g = not pancreatic insuffiency
Most specific and sensitive non-invasive measure in insufficiency (but not great at mild insufficiency)
Outline the NBT-PABA test
Chemotrypsin comberts NBT-PABA to NBT and PABA
PABA in absorbed, conjugated by liver and excreted urine. Collect urine sample and measure PABA - proportional to chemotyrpsin excreted by pancreas
Is affected by intestine absorption, liver and kidney function
