Ch 97 - Pancreas Anatomy

Question 1

What percentage of total pancreatic mass is exocrine?

Answer 1

98%

Question 2

What cells form the endocrine pancreas? List all 4 types of this cell and what they produce

Answer 2

Endocrine pancreas is composed of Islets of Langerhans

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

Question 3

What is the function of acinar cells?

Answer 3

Produce digestive enzymes within the pancreatic lobules and make up the duct system for that lobule

Question 4

Describe the blood supply to the pancreas

Answer 4

Main blood supply is from the coeliac artery with the splenic artery supplying most of the left limb. The hepatic artery becomes gastroduodenal artery that terminates as the cranial pancreaticoduodenal artery and supplies the cranial right limb and duodenum. The cranial mesenteric artery also supplies a branch called the caudal pancreaticoduodenal artery which anastomoses with the cranial pancreaticoduodenal artery within the right limb.

Question 5

What is the innervation to the pancreas?

List the innervation to the:

• Blood vessels
• Acinar and islet cells
• Stimulation/inhibition of pancreatic juice secretion

Answer 5

Pancreas is innervated by the enteric nervous system and braches of the vagus n,

• Blood vessels - coeliac and superior mesenteric plexus
• Acinar and islet cells - cholinergic neurons that synapse with vagal fibres
• Pancreatic juices - stimulated by parasympathetic and inhibited by sympathetic

Question 6

Descrive the typical anatomy of the pancreatic ducts in dogs and cats.

List the main forms of anatomical variation.

Answer 6

68% of dogs have the typical anatomy.
The left and right ducts conjoint to form a Y with the tail of the Y forming the accessory pancreatic duct (Duct of Santorini), entering the duodenum through the minor duodenal papilla. A second duct (pancreatic duct or Duct of Wirsung), enters the duodenum adjacent to the CBD at the major papilla. The accessory is the larger of the two and secretes the majority of the pancreatic secretions.

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

Variations - Accessory duct alone in dogs, presence of 3 duodenal openings in dogs, presence of accessory duct in cats (20%)

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 concentration as well as FAs and amino acids, stimulating intracellular conversion of these compounds into glycogen, triglycerides and protein respectively for storage.

Glucagon secretion - Secreted in response to hypoglycaemia. Mobilises energy stores by increasing glycogenolysis, gluconeogenesis and lipolysis,

Question 9

What is a zymogen?

List the 4 types of pancreatic zymogen

How are the pancreatic zymogens activated?

Answer 9

Zymogens are an inactive precursor 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 movement of food into the proximal duodenum stimulate pacreatic secretion?

Answer 10

Duodenal mucosal cells secrete secretin and cholecystokinin

• Secretin –> stimulates large vlumes of bicarb rich fluid secretion from the pancreas
• Cholecystokinin –> Stimulates secretion of digestive enzymes from the pancreas, Also stimulates contraction of the gallbladder and relaxation of the sphincter of Oddi

Question 11

What pre-medication should be avoided in animals undergoing pancreatic surgery

Answer 11

alpha-2 agonists - In normal animals these medications cause hypoinsulinaemia and hyperglycaemia but their effect in the face of a disease pancrease in unpredictable

Question 12

What part of the pancreas is recommended for pancreatic biopsy?

List the options for performing a pancreatic biopsy

Is there a reported clinical or histological difference between biopsy techniques?

Answer 12

Distal right limb of the pancrease is the idea location - Good distance from the duct system, easily accessible and its vascular supply is not the primary blood sorce to other organs

• Tru-Cut
• Punch biopsy
• Wedge biopsy
• Blunt dissection
• Suture fraction

Studies have shown no clinical difference or difference in amylase and lipase measurements between biopsy techniques. Histo exam showed a more severe inflammatory reaction in those undergoin suture fraction however there was no clinical significance to this finding.

Question 13

How much pancreas can be removed without impairing the endocrine or exocrine function?

Answer 13

75 - 95% can be removed as long as the duct to the remaining pancreas is left intact

Question 14

What is the main limiting factor of total pancreatectomy?

Answer 14

Maintaining duodenal blood supply.

Question 15

List the main considerations for post-op care in patients undergoing pancreatic surgery

Answer 15

• Nutrition - need for a feeding tube placement during surgery?
• Fluid support - Need for colloids?
• Analgesia - Opioids, but can cause ileus, constipation, vomiting. Consider ketamine and lidocain CRIs also
• Antiemetics
• Gastric Acid Reduction - if evidence of gastroduodenal ulceration or oesophagitis

Question 16

How does maropitant work?

Answer 16

Blocks centrally and peripherally mediate emesis through blockage of neurokinin-1 receptors and substance P production

Blockage of neurokinin-1 receptors could also reduce visceral pain and lung injury