TBL18 - Pancreas

Question 1

Similar to the distal duodenum and kidneys, the pancreas is what type of organ with respect to location within the abdominal cavity? Where does the pancreas reside?

Answer 1

1) Like the distal duodenum and kidneys, the pancreas is a retroperitoneal organ
2) The pancreas resides on the posterior abdominal wall adjacent to the bodies of vertebrae L2 and L3

Question 2

What covers the anterior surface of the pancreas?

Answer 2

The parietal peritoneum that forms the floor of the lesser sac covers the anterior surface of the pancreas

Question 3

What structures are found around the head of the pancreas? The neck of the pancreas? The body of the pancreas? The tail of the pancreas?

Answer 3

1) Head of the pancreas: C-curve of duodenum, bile duct, and IVC
2) Neck of the pancreas: SMA and hepatic portal vein
3) Body of the pancreas: abdominal aorta and left kidney
4) Tail of the pancreas: hilum of spleen

Question 4

What is the name of the space separating the stomach and first part of the duodenum from the pancreas?

Answer 4

Omental bursa (lesser sac)

Question 5

What is the head of the pancreas supplied by? What are the neck, body, and tail supplied by? Where does venous blood drain into?

Answer 5

1) The head of the pancreas is supplied by the superior and inferior pancreaticoduodenal arteries
2) The neck, body, and tail are supplied by the splenic artery
3) Venous blood from the pancreas drains into the hepatic portal vein

Question 6

What is the pancreas innervated by?

Answer 6

The pancreas as a foregut derivative is innervated by periarterial plexuses on branches of the celiac trunk

Question 7

What do sympathetic fibers of the periarterial plexuses induce in the pancreas? What is pancreatic secretion controlled by?

Answer 7

1) Sympathetic fibers of the plexuses induce vasoconstriction
2) Although the vagal fibers are secretomotor, pancreatic secretion is mainly under hormonal control (cholecystokinin)

Question 8

What causes visceral pain of the pancreas and where is it referred to? If the parietal peritoneum covering the anterior surface of the pancreas is distended or irritated, where is pain triggered?

Answer 8

1) Distension or irritation of the pancreas creates visceral pain, which is referred to the epigastric region
2) If the parietal peritoneum covering the anterior surface of the pancreas is subsequently distended or irritated, activation of somatic sensory fibers that supply the parietal peritoneum triggers sharp, localized, back pain

Question 9

What forms the hepatopancreatic ampulla on the descending (2nd) part of the duodenum? What does this site demarcate?

Answer 9

1) Union of the main pancreatic duct to the bile duct forms the short, dilated hepatopancreatic ampulla on the descending (2nd) part of the duodenum
2) This union demarcates the foregut- and midgut-derived portions of the duodenum

Question 10

What do smooth muscle sphincters of the bile duct, pancreatic duct, and hepatopancreatic ampulla control? What do they prevent?

Answer 10

1) Smooth muscle sphincters of the bile duct, pancreatic duct, and hepatopancreatic ampulla control the flow of bile and pancreatic enzymes into the duodenum
2) They also prevent reflux of duodenal content into the ampulla

Question 11

What does tonic contraction of the sphincters normally limit? What does the release of cholecystokinin activate?

Answer 11

1) Tonic contraction of the sphincters normally limits flow into and reflux from the ampulla
2) The release of cholecystokinin activates gallbladder contraction and relaxes the sphincters

Question 12

Why can spasms of the hepatopancreatic sphincter or obstruction of the hepatopancreatic ampulla by gallstones cause pancreatitis?

Answer 12

1) Normally, the sphincter of the pancreatic duct prevents reflux of bile into the pancreatic duct; however, if the hepatopancreatic ampulla is obstructed, the weak pancreatic duct sphincter may be unable to withstand the excessive pressure of the bile in the hepatopancreatic ampulla
2) Bile may back up and enter the pancreatic duct, usually resulting in pancreatitis (inflammation of the pancreas)
3) A similar reflux of bile sometimes results from spasms of the hepatopancreatic sphincter

Question 13

Why can severe, forceful compression of the abdomen rupture the pancreas and why would sharp, local pain result?

Answer 13

1) Pancreatic injury can result from sudden, severe, forceful compression of the abdomen, such as the force of impalement on a steering wheel in an automobile accident. Because the pancreas lies transversely, the vertebral column acts as an anvil, and the traumatic force may rupture the friable pancreas
2) Rupture of the pancreas frequently tears its duct system, allowing pancreatic juice to enter the parenchyma of the gland and to invade adjacent tissues. Digestion of pancreatic and other tissues by pancreatic juice is very painful
3) Parietal peritoneum pressure causes sharp local back pain

Question 14

How does pancreatic cancer cause jaundice and why does the cancer have a high fatality rate?

Answer 14

1) Cancer involving the pancreatic head accounts for most cases of extrahepatic obstruction of the biliary ducts
2) This causes obstruction, resulting in the retention of bile pigments, enlargement of the gallbladder, and obstructive jaundice
3) The pancreas’s extensive drainage to relatively inaccessible lymph nodes, and the fact that pancreatic cancer typically metastasizes to the liver early, via the hepatic portal vein, make surgical resection of the cancerous pancreas nearly futile

Question 15

Where does the main pancreatic duct extend from and to?

Answer 15

The main pancreatic duct extends from the tail to the head of the pancreas

Question 16

Where do exocrine acini of the pancreas secrete into? What do the dark stained cells of the secretory acini secrete, under what influence, and at what rate?

Answer 16

1) Exocrine acini of the pancreas secrete into small ducts (ignore intercalated duct) that empty into the main duct along its entire length
2) The dark stained (aka serous) cells of the secretory acini secrete digestive enzymes, mainly under the influence of cholecystokinin, at a rate of 1-2 L/day

Question 17

Where are the pancreatic islets of Langerhans located? How are beta and alpha cells identified under a microscope?

Answer 17

1) The pancreatic islets (of Langerhans) are scattered among the acini of the exocrine pancreas
2) Selective staining of the hormones, insulin and glucagon, identifies beta and alpha cells, respectively

Question 18

Where do secretions of the endocrine pancreas travel?

Answer 18

Unlike the exocrine pancreas, secretions from beta and alpha cells of the endocrine pancreas enter the bloodstream via a network of capillaries, which abuts each islet cell

Question 19

How does insulin lower blood glucose? How does glucagon raise blood glucose?

Answer 19

1) Insulin lowers blood glucose mainly by prompting glucose entry into hepatocytes, adipocytes, and skeletal muscle fibers
2) Glucagon raises blood glucose mainly by activating hepatocytic glycogenolysis

Question 20

How can acute pancreatitis become life-threatening?

Answer 20

1) Acute pancreatitis is an inflammatory disorder of the exocrine pancreas often associated with alcoholism or excessive alcohol intake
2) Acinar cell injury or pancreatic duct obstruction may lead to inappropriate extracellular leakage of activated digestive enzymes and autodigestion of pancreatic acini
3) Edema and progressive fibrosis of the stroma may ensue and cause hemorrhage and ultimately pancreatic insufficiency