Pancreas And GI tract Physiology

Question 1

What is the GI tract?

Answer 1

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

Question 2

What is peristalsis?

Answer 2

Symmetrical contraction and relaxation of smooth muscles that propagates in a wave down a tube

Question 3

What types of absorption happen in the intestines?

Answer 3

95% small nutrient absorption in small intestine

Large intestine : absorption of fluid

Question 4

How is the GI tract regulated?

Answer 4

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

Question 5

What are the three stages of digestion and absorption?

Answer 5

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

Question 6

What are the main functions of the stomach?

Answer 6

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

Question 7

What are the actions of gastrin?

Answer 7

Stimulate: gastric acid release, secretion of pancreatic juices, secretion of pepsinogen and secretion of somatostatin

Question 8

What are the three sections of the small intestine?

Answer 8

Duodenum, jejunum and ileum

Question 9

What are the functions of the pancreas?

Answer 9

Endocrine: secretes insulin, glucagon and somatostatin
Exocrine: secretes pancreatic juice: fluid, bicarbonate, electrolytes and enzymes

Question 10

Why are bile acids needed?

Answer 10

To emulsify non-water soluble fats (triglycerides, cholesterol, fat-soluble vitamins)

Question 11

What happens following emulsification?

Answer 11

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.

Question 12

What are the symptoms of malabsorption?

Answer 12

Diarrhoea, statorrhea, malnutrition, abdominal pain, abdominal distension

Question 13

What tests would be used to confirm malabsorption?

Answer 13

Biochem: U&E, calcium and albumin and Mg+
Heam: FBC, Folate, vit B12, iron, ferritin, prothrombin time

Question 14

What are the investigations of gastric function?

Answer 14

H. pylori in peptic ulcer disease

Fasting gastrin in Zollinger-Ellison syndrome

Question 15

What investigations could be used for intestinal function?

Answer 15

TTG antibodies and then endomysial antibodies if positive
Hydrogen breath test - lactose intolerance
Markers of inflammation - CRP/ESR (non-specific) or faecal calprotectin (specific)

Question 16

What is faecel calprotectin?

Answer 16

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

Question 17

What are the pancreatic function tests?

Answer 17

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

Question 18

How do the invasive pancreatic function tests work?

Answer 18

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.

Question 19

How do the non-invasive pancreatic function tests work?

Answer 19

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)

Question 20

What are breath tests?

Answer 20

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

Question 21

What is the faecel elastase test?

Answer 21

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)

Question 22

Outline the NBT-PABA test

Answer 22

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