Pancreatic Physiology

Question 1

Understand the role of the exocrine pancreas in digestion

Answer 1

Acinar cells produce and secrete digestive enzymes (amylase, lipase, colipase, phospholipase and proteases)

Duct cells secrete sodium bicarbonate

• 98 % of parenchyma is exocrine
• Release is stimulated by hormonal and neural signals

Question 2

Describe the structure and function of pancreatic acini

Answer 2

Functional unit is an acinus: Acinar cells surround a draining ductule. Ductules drain into interlobular ducts. Acinar cells: Rich in R.E.R. Acinar cells store digestive enzymes within granules and then secretes then by exocytosis. The enzymes are then transported to the duodenum by pancreatic juice. Secretion of water: Interrupted in CF. Chloride cannot move out into the lumen, Na and H2O cannot follow. Leads to an inability to secrete digestive enzymes as the ducts are blocked by thick mucous.

Question 3

Mechanisms to prevent/limit autodigestion of the acinar cells by digestive enzymes

Answer 3

1. Secretion of zymogen granules: Calcium and cAMP modulate release. Receptor mediated as well e.g. secretin
2. Preventing autodigestion: In secretory vesicles, in an inactive state and packaged with a trypsin inhibitor.
3. Activation by enterokinase @ the brush border: Trypsinogen is cleaved by enterokinase. Trypsin can then activate other zymogens. No enterokinase → No activation

Question 4

Understand the role of Secretin, Gastrin, and CCK in regulating pancreatic secretion

Answer 4

Secretin: Increases release of bicarbonate ions from the pancreatic duct cells. Enhances the effects of CCK

Gastrin: From G cells. Acts upon parietal cells to cause HCl secretion.

CCK: Increases pancreatic secretion of digestive enzymes from acinar cells.

Question 5

Describe the enzymatic products of the pancreas and their respective roles in digestion = PANCREATIC JUICE

Answer 5

Duct cells secrete bicarbonate. Acts to neutralise the chyme received from the stomach. Reduces damage to the stomach and also creates an optimum pH for enzymatic activity. This is prompted by secretin. Acinar cells secrete digestive enzymes: Allow digestion of multiple macromolecules and subsequent absorption,

Question 6

Targeting pancreatic juice to prevent digestion and absorption

Answer 6

Pancreatic lipase has been targeted for the treatment of obesity (orlistat)

Question 7

Disorders of the exocrine pancreas

Answer 7

Diabetes: Lack of insulin production (type I) Duct obstruction and abuse to cells lead to acinar damage and ultimately pancreatitis