Chapter 19 Flashcards
The exocrine pancreas makes up _% of the organ
80-85
What is the exocrine pancreas composed of
Acinar cells that secrete enzymes for digestion
In the exocrine pancreas, __ are carried by ducts to duodenum for activation via proteolytic cleavage
Pronzymes
What are acinar cellls
Pyramid shaped epithelial cells with membrane bound granules rich in proenzymes (zymogens ) like trypsinogen, chymotrypsinogen, procarboxypeptidase, proelastase, kallikreinogen, and phospholipase A and B
What is the endocrine pancreas
Islet of langerhan
What are inslets of langerhans
Cell clusters throughout the gland that secrete insulin, glucagon, and somatostatin
What percentage of the pancreas is endocrine pancreas
1-2%
In the embryo, what does the dorsal primordium become
Body, tail, and superior/anterior aspect of the head of the pancreas; accessory duct of santorini
In the embryo, what does the ventral primordium become
Posterior/inferior part of the head of the pancreas; main pancreatic duct (the duct of wirsung)
What is the most common congenital anomaly of the pancreas
Pancreas divisum
Why get pancreas divisum
Failure of the ventral and dorsal fetal duct systems to fuse properly
What does the main pancreatic duct of wirsung do
Drains only a small portion of the head of the gland through the papilla of vaster
Where do the majority of pancreatic secretions drain
Small caliber, minor papilla rather than the papilla of vater
What are people with pancreas divisum predisposed to
Chronic pancreatitis
What is an annular pancreas
Band like ring of normal pancreatic tissue that encircles the second portion of the duodenum
What can annular pancreas cause
Duodenal obstruction
Ectopic pancreas symptoms
Usually symptomatic, but at aberrant sites may lead to pain from localized inflammation( or rarely mucosal bleeding)
What are most common sites of ectopic pancreas
Stomach, duodenum, jejunum, meckel diverticula, ileum
Genetics of pancreatic agenesis
Homozygous mutation of PDX1
What does PDX1 code
Gene normally encodes homeobox transcription factor critical for pancreatic development
How does the pancreas protect itself
Synthesis of proenzymes packaged in secretory granules-biochemically separate
Duodenal enteropeptidase
Trypsin inhibitors
Duodenal enteropeptidase(enterokinase)
In the small bowel activates trypsin which activates other proenzymes-anatomically separate
-intrapancreatic activation of proenzymes is normally minimal
Trypsin inhibitors
Secreted by acinar and ductal cells
-serine protease inhibitor Kazan type I (SPINK1) further limits intrapancreatic trypsin activity
Failure of pancreatic protection mechanisms
Pancreatitis
Acute pancreatitis
Reversible pancreatic parenchymal injury associated with inflammation due to diverse etiologies
80% of acute pancreatitis is caused by what
Alcoholism and biliary tract disease
What is th the ratio of male to female with acute pancreatitis caused by alcoholism
6:1
What is the ratio of females to males that get acute pancreatitis from biliary disease (cholelithiasis)
3:1
Pathogenesis of acute pancreatitis: three initiating events that lead to autodigestions
Duct obstruction, primary acinar icell injury, and defective intracellluar transport of proenzymes within acinar cells
Pathogenesis of acute pancreatitis: what causes parenchymal autodigestion
Inappropriate release and activation of pancreatic enzymes (trypsinogen)
- degradation of fat cells (phospholipase), damage to elastic fibers of blood vessels (elastase)
- pre-kallikrein leads to kallikrein which activated the kinin system and clotting(factor XII) and complements systems
- produces inflammation and thrombosis which further damage acinar cells and amplify the intrapancreatic activation of digestive enzymes
Acute pancreatitis : duct obstruction
- raises intrapancreatic ductal pressure and leads to accumulation of enzymes rich fluid in the intertitium
- lipase (secreted in an active form) has potential for local fat necrosis
- death of pancreatic tide releases “danger signals’ locally that stimulate parenchymal release of proinflammatory cytokines
- interstitial edema through a leaky microvascularization
- inflammation and interstitial edema compromise vascular flow, increased ischemia to the ongoing parenchyma injury
- due to gallstones, periampullarry neoplasms, choledochoceles (congenital cystic dilation of the common bile duct), parasites (espicially ascaris lumbricoides and clonorchis sinesis) and possible pancreatic divisum
Acute pancreatitis: primary acinar cell injury
Leads to release of digestive enzymes->inflammation and autodigestion
What causes primary acinar cell injury
- oxidative stress: free radicals-> membrane lipid oxidation-?AP1 and NFKB==pro-inflammatory
- Low ca: trypsin cleaves and inactivated itself
- high Ca autoinhibition is abrogated and activation of trypsinogen by trypsin is favored
Acute pancreatitis: defective proenzyme transport
Exocrine enzymes are misdirected to lysosomes rather than to secretion
Lysosomal hydrolysis of the proenzyme leads to activation and release
What is the most likely etiology of acute pancreatitis
Alcohol consumption
How does alcohol cause acute pancreatitis
- direct toxic effect on acinar cells
- alcohol induced oxidative stress->free radicals->lipid peroxidation->free radicals->AP1 and NFKB==pro-inflammatory
Alcohol consumption and acute pancreatic causes transiently increased contraction of what
Sphincter of oddi (muscle at papilla of vater)
Acute pancreatitis: chronic alcohol consumption causes secretion of what
Protein rich pancreatic fluid causing inspissated protein plugs that block small ducts
Does chronic alcohol consumption commonly cause acute pancreatitis
Most do not, those who do, do after many years of abuse
What are some other triggers of acute pancreatitis
Metabolic disorders:hyperTG, hyperCa, hyperPTH
Genetic lesions:40% increased risk f prostate cancer
Medications:furosemide, azathioprine, estrogens
Trauma or ischemia to acinar cells
Infection:mumps
Hereditary pancreatitis: characterized by recurrent attacks of severe acute pancreatitis and ultimately leading to chronic pancreatitis
Hereditary pancreatitis
Recurrent attacks of severe acute pancreatitis and ultimately leading to chronic pancreatitis
Shared feature of hereditary pancreatitis
Shared feature of most forms is a defect that increases or sustains the activity to trypsin
Genetic mutations of hereditary pancreatitis
PRSS1
PSINK1
CFTR
PRSS! Hereditary pancreatitis
Gain fo function mutation of trypsinogen making trypsin resistant to self inactivation or prone to activation
Most common
AD
SPINK1 hereditary pancreatitis
Loss of function preventing inhibition of trypsin
AR
CFTR hereditary pancreatitis
Decreased bicarbonate secretion leads to protein plugins, duct obstruction, and pancreatitis
Patients with hereditary pancreatisi have a 40% chance of developing __ __
Pancreatic cancer
Morphology acute pancreatitis
Microvascular leakage leads to edema
Fat necrosis by lipolysis enzymes, released fatty acids combine with Ca that give a granular blue look to fat cells (saponofication)
Proteolytic destruction of the pancreatic parenchyma
Vascular injury with subsequent interstitial hemorrhage that appears red black with foci of yellow white chalky fat necrosis
Peritoneal cavity: serous, slightly turbid, brown fluid with fat globules
Acute pancreatitis presentation
Constant abdominal pain, may refer to upper back or L shoulder
Anorexia, nausea, vomiting
Labs acute pancreatitis
Increased plasma levels of amylase (24 hours), lipase (72096 hours)
10% glycosuria
Hypocalcemia due to deposition of Ca soap formation in necrotic fat (saponification)
Full blown acute pancreatitis
Acute abdomen (intense pain)
Peripheral vascular collapse
Shock due to activation of systemic inflammatory response syndrome (SRS)
- leukocytosis, disseminated intravascular coagulation, edema, ARDS (shock and acute renal tubular necrosis may occur)
- LIFE THREATENING EMERGENCY
Treatment acute pancreatitis
Total restriction of oral intake to rest the pancreas
IV fluids and pain meds
Nutrition+volume support
Function returns to normal if resolved
Complications acute pancreatitis
5% will die int he first week of severe acute pancreatitis
ARDS and acute renal failure
Sterile pancreatic abscess
Pancreatic pseudocyst
Infection of necrotic debris by gram -ve pathogens from alimentary tract
Chronic pancreatitis
Prolonged inflammation of the pancreas due to irreversible destruction of exocrine parenchyma, fibrous and eventually, the endocrine parenchyma
Who gets chronic pancreatitis
Middle age males
Causes of chronic pancreatitis
Long term alcohol use
Longstanding obstruction by calculi or neoplasm
Autoimmune injury
25% of chronic pancreatitis has a genetic component
Chronic pancreatitis often follows repeated bouts of __ ___
Acute pancreatitis
Chronic pancreatitis leads to perilobular fibrosis, duct distortion and altered secretions that can lead to what
Loss of parenchyma
Fibrosis
In chronic pancreatitis there is production of fibrogenic inflammatory mediators TGFB and PDGF
Induces activation and proliferation of periacinar myofibroblasts (pancreatis stellate cells)->deposition of collagen and fibrosis
Morphology chronic pancreatitis
Fibrosis, atrophy and dropout of acini
Variable dilation of pancreatic ducts
Pancreas is hard with focal calcification
Relative sparing of islet of langerhans
Chronic pancreatitis caused by alcohol abuse is characterized by ductal dilation, intraluminal protein plugs and calcification
Symptoms chronic pancreatitis
Usually silent, but there may be recurrent attacks of pain and/or jaundice
What triggers chronic pancreatitis
ETOH, overeating (increased demand) or opiates that increase tone of sphincter of oddi
With chronic pancreatitis, ____ __ and ___ eventually develop due to destruction of exocrine and endocrine organ
Pancreatic insufficiency
DM
Prognosis chronic pancreatitis
Not usually life threatening
20-25 year=50% mortality
How diagnose chronic pancreatitis
Clinical suspicion
Amylase levels are not always elevated and fever not always present due to acinar cells
Visualization of calcification in the pancreas via CT or ultrasonography
Weight loss and edema due to hypoalbuminemia from malabsorption
Complications chronic pancreatitis
Malabsorption, DM, pseudocysts (10%)