Lecture 25 - Pancreatic and Biliary Secretions

Question 1

Central role of duodenum?

Answer 1

Inhibit gastric emptying, inhibit gastic secetion, stiulate pancreatic and biliary secretion

Question 2

Mechanism for these roles?

Answer 2

Endocrine cells responsing to nutrients, vagal afferents responding to luminal contents

Question 3

I Cell mechanims?

Answer 3

apical surface detects partially digested fats and proteins, stimulates cholecystokinin release from basolateral surface

Question 4

S Cell Mechanism?

Answer 4

Apical surface senses low pH in duodenum, secretes secretin from basolateral surface

Question 5

Enterochromaffin cell mechanism?

Answer 5

Apical surface of cell senses food or irritant, stimulate serotonin release from basolateral surface

Question 6

Serotonin function?

Answer 6

stimulates gut motility, high levels lead to vomiting

Question 7

Exocrine secretions?

Answer 7

Digestive enzymes for fat and protein digestion, bicarbonate ions to neutralise acidity

Question 8

Bicarbonate secreted from?

Answer 8

Ductile cells

Question 9

Acinar cell contents?

Answer 9

Secretory granules filled with enzyme precursors (zymogens) which are released into intestine via pancreatic duct; as well as rER for enzyme production

Question 10

Activation of proenzymes occurs where?

Answer 10

duodenal brush border (lumen) via proteolytic cleavage (roduced trypsin can be auto-catalytic)

Question 11

pathways of CCK mechanism?

Answer 11

through bloodstream to acinar cells stimulating enzyme release; afferent nerves to vagus nerve in brainstem which sends efferent signal to pancreas stimulating release

Question 12

Purpose of neutral duodenal pH?

Answer 12

Protect mucosa, deactivate pepsin, activate pancreatic and brush border enzymes, increase fatty acid and bile acid solubility

Question 13

Enzyme and ion transporte in bicarbonate release?

Answer 13

Carbonic anhydrase, CFTR transporter

Question 14

Other factors increasing pancreatic enzyme release?

Answer 14

Gastrin; vagus stimulation causing Ach release (also stimulate bicarbonate release from apicar cell)

Question 15

CCK other functionS?

Answer 15

Bile production in liver, gallbladder contraction, sphincter of Oddi relaxation

Question 16

Cystic Fibrosis mechanism?

Answer 16

Mutation of CFTR gene hindering in channel function, secretions thicken blocking passage

Question 17

CFTR characteristics?

Answer 17

chloride channel involved in production of sweat, mucus and digestive fluids, plays role in bicarbonate secretion

Question 18

reason for mucus thickening?

Answer 18

Chloride accumulates in ductile cells, negative charge draws in Na+ ions then water causing hyperviscousity

Question 19

Bile passage through biliary tree?

Answer 19

Secreted by hepatocytes, enters canaliculi and flows into large bile ducts, ductal cells add bicarbonate, , leaves liver, follows common hepatic duct and enters cystic duct into gallbladder

Question 20

Cholestasis leads to?

Answer 20

increase pressure in biliary tract and liver, rupture of tight junctions causing bile leakage, bile spilt into circulation causing jaundice (hyperbilirubinaemia)