Chapter 97: Pancreas

Question 1

What percentage of total pancreatic mass is exocrine?
Endocrine?

Answer 1

98% Exocrine

2% Endocrine

Question 2

What cells form the endocrine pancreas?

Answer 2

Endocrine pancreas is composed of Islets of Langerhans, which form cords nestled in the pancreatic nodules.

Question 3

What cells form the exocrine pancreas?

Answer 3

Acinar cells - produce digestive enzymes
Ductal cells - form ducts in the lobules

Question 4

What is the blood supply to the pancreas?

Answer 4

Celiac artery via -> splenic and hepatic aa.

The splenic artery supplies the left limb.

The hepatic artery -> cranial pancreaticoduodenal artery and supplies the cranial right limb and duodenum.

Cranial mesenteric artery -> caudal pancreaticoduodenal artery supplies distal right limb and anastomoses to the cranial.

Question 5

What is the innervation to the pancreas?

What stimulates secretion of pancreatic juices?

Answer 5

Pancreas is innervated by the enteric nervous system and branches of the vagus nerve.

Acinar and islet cells innervated by cholinergic neurons that synapse with vagal fibers.

Pancreatic juice secretion is stimulated by parasympathetic and inhibited by sympathetic.

Question 6

Describe the typical anatomy of the pancreatic ducts in dogs and give the main forms of anatomical variation:

Answer 6

In 68% of dogs the left and right ducts conjoin to form a Y with the tail of the Y forming the LARGER accessory pancreatic duct (Duct of Santorini), entering the duodenum through the minor duodenal papilla.
A second duct (pancreatic duct or Duct of Wirsung), comes off one of the two main L/R ducts before the Y and enters the duodenum adjacent to the CBD at the major papilla.

Variations - Accessory duct alone, presence of 3 duodenal openings.

Question 7

What are the main physiologic functions of the pancreas?

Answer 7

Glucose metabolism (Islet cells - endocrine ) and digestion (acinar cells - exocrine )

Question 8

How do the islet cells regulate glucose metabolism?

Answer 8

Insulin secretion decreases blood glucose, fatty acids, and amino acids. -> Stimulates intracellular conversion of these compounds into glycogen, triglycerides and proteins for storage.

Glucagon secretion (in response to hypoglycemia). Controls the glucose influx from hepatocytes and mobilizes energy stores by increasing glycogenolysis, gluconeogenesis and lipolysis.

Question 9

What is a zymogen?

List the 4 types of pancreatic zymogens?

How are the pancreatic zymogens activated?

Answer 9

Zymogens are inactive precursors of digestive enzymes secreted by the pancreas.

Types: Trypsinogen, chymotrypsinogen, proelastases, procarboxypeptidases

Actived via the activation of trypsinogen into trypsin by enterokinase, produced by the duodenal enterocytes. Trypsin then in turn activates the other zymogens via proteolytic cleavage.

Question 10

How does presence of food in the proximal duodenum stimulate pancreatic secretion?

Answer 10

Food -> duodenal mucosal cells secrete secretin and cholecystokinin.

Secretin –> stimulates large volumes of bicarbonate rich fluid secretion from the pancreas (from acinar cells)

Cholecystokinin –> Stimulates secretion of digestive enzymes from the pancreas (also from acinar cells)

Question 11

What are the four endocrine cell types within the Eyelets of Langerhans and what does each produce?

Answer 11

Alpha cells - glucagon
Beta cells - Insulin
Delta cells - somatostatin
F or PP cells - Produce pancreatic polypeptide

Question 12

What is the major difference between dogs and cats pancreatic ducts?

Answer 12

80% of cats do NOT have an accessory pancreatic duct and their pancreatic duct fuses with the CBD prior to entering at the papilla.

Question 13

What is the Duct of Wirsung also called?

How about the Duct of Santorini?

Answer 13

Duct of Wirsung = pancreatic duct, comes from the main duct of right or left lobe and enters at major papilla with the CBD.

Duct of Santorini = Accessory pancreatic duct. From the tail end of the Y. It is larger and enters at the minor papilla.

Question 14

Where does the right lobe of the pancreas sit?

Answer 14

Closely associated with the proximal duodenum, in the mesoduodenum. It is the easiest to access.

Question 15

Where is the Left lobe of the pancreas found?

Answer 15

in the dorsal leaf of the greater omentum. It begins near the pylorus and extends along the greater curvature of the stomach.

Question 16

Where is the body of the pancreas?

Answer 16

At the proximal duodenum.

Question 17

How does the pancreas prevent autodigestion by its own enzymes?

Answer 17

1. Enzymes are stored as inactive zymogens
2. The zymogens are segregated into membrane-bound granules
3. The acinar cells make a pancreatic secretory trypsin inhibitor that is stored with the zymogens

Question 18

What are the inorganic secretions of the exocrine pancreas?

What is intrinsic factor?

Answer 18

Na, K, Cl Bicarb

Intrinsic factor is another secretion that helps the ileum to absorb cobalamin.

Question 19

Anticipation or scent of food causes what?

Answer 19

Vagal stimulation that causes pancreatic secretion.

Question 20

What happens when the pancreas is injured?

How does it heal?

Answer 20

Disruption of acinar cells -> enzymes released -> inflammation! The inflammatory cascade can lead to necrotizing pancreatitis.

Heals with fibrosis - may be irreversible in chronic cases.

Question 21

What is the major important component of anesthesia for pancreatic conditions?

Answer 21

Hypoglycemic management. May need dextrose support, a sampling line to check BG, etc.
Avoid alpha 2 drugs as they can cause weird effects in patients with pancreatic issues (usually they cause hyperglycemia but WEIRD).
Propofol or etomidate may be neuroprotective in the face of low sugar.