Chapter 14 Flashcards
From which two endodermal tissues does the pancreas develop?
When in development does this begin?
Dorsal and ventral pancreatic buds
4th wk of gestation
Position of the pancreas
Lies retroperitoneal, posterior to the stomach at the level of the first and second lumbar vertebrae
Composition of the pancreas
Head Uncinate process Neck Body Tail
Position of head of the pancreas
Rests within the C-loop of the duodenum to the right of the midline
Uncinate process
An inferior projection of the head, which curves posterior to the superior mesenteric vessels and anterior to the IVC
Neck of the pancreas
The portion of the pancreas that lies anterior to the portal vein and superior to mesenteric vessels
Body of the pancreas
To the left of the mesenteric vessels
Lies superior to the fourth portion of the duodenum and forms the floor of the lesser sac
Tail of the pancreas
The smallest portion of the pancreas
Lies in proximity to the splenic hilum
Blood supply of head and uncinate process
Vast majority is supplied by anterior and posterior superior and inferior pancreaticoduodenal arteries
Superior pancreaticoduodenal artery branches
Branches off the gastroduodenal artery, which emanates from the celiac axis
Inferior pancreaticoduodenal artery pathway
Arises from the SMA
Blood supply to body and tail of the pancreas
Branches of the splenic and left gastroepiploic arteries supply the distal body and tail of the pancreas
Within the posterosuperior and posteroinferior aspect of the body of the pancreas lie the superior and inferior pancreatic arteries, respectively
Venous drainage of the pancreas
Parallels its arterial supply
All drainage ultimately enters the portal vein, which is formed posterior to the neck of the pancreas by the confluence of the splenic and SMVs
Sympathetic pathway of the pancreas
Preganglionic sympathetic axons arise from cell bodies withint he thoracic sympathetic ganglia and travel as splanchnic nerves terminating within the celiac ganglia
Postganglionic sympathetic fibers traverse retroperitoneal tissue to innervate the pancreas and serve as the principal pathways for pain of pancreatic origin
Parasympathetic innervation
Preganglionic fiber cell bodies that reside within the vagal nuclei and travel through the posterior vagal trunk.
These axons traverse the celiac plexus and terminate in parasympathetic ganglia within the pancreatic parenchyma
Short postganglionic parasympathetic fibers then innervate the pancreatic islets, acini, and ducts, serving an exclusively efferent function
What are the two general categories of cellular components of the pancreas?
Exocrine
Endocrine
What are the primary exocrine units of the pancreas?
Acinar cells
How are acinar cells connected?
Connected to each other by a network of tubules and ducts, which eventually drain into the duodenum
Types of islet cells
Alpha
Beta
Delta
What does each islet consist of?
A core composed of beta cells
A peripheral mantle composed of alpha, delta, and pancreatic polypeptide cells
How much does the exocrine pancreas produce?
Up to 20 g of digestive enzymes and 2.5 L of bicarb-rich fluid each day.
Purpose of the acinar cells
Responsible for the production of enzymes
Purpose of the ductal cells
Secrete fluid and electrolytes under both vagal and humoral control
Sodium and potassium concentrations and exocrine physiology
Remain constant and are approximately equivalent to plasma concentrations
Anion concentration of pancreatic exocrine secretion
Dependent on secretory rate
What is the most potent endogenous stimulant of pancreatic bicarb secretion?
Secretin
Where is secretin synthesized?
In the mucosal S cells of the crypts of Lieberkuhn of the proximal small bowel and is released int he presence of luminal acid and bile
Physiology of secretin
Circulates in the blood and binds to secretin receptors on pancreatic ductal cells, effecting signal transduction through the intracellular adenylate cyclase system
The resultant bicarb secretion serves to neutralize stomach acid that enters the duodenum
What are the other components of exocrine pancreatic juice?
Digestive enzymes, which aid in amino acid, lipid, and complex carbohydrate breakdown
What are the three phases of the contribution of the pancreas to digestion?
Cephalic phase
Gastric phase
Intestinal phase
Cephalic phase
Stimuli (smell and taste) activate vagal efferent signals, which stimulate pancreatic enzyme release
The net effect of cephalic phase stimulation is the secretion of an enzyme-rich, bicarb-poor fluid
Gastric phase
Antral distention and protein delivery stimulate the release of gastrin
Gastrin promotes gastric acid secretion from parietal cells and also serves as a weak stimulant for pancreatic enzyme secretion
Acidification of the duodenum in turn leads to secretin release, which stimulates pancreatic bicarb secretion.
Intestinal phase
Secretin and CCK serve a major function in mediating pancreatic exocrine secretion
Duodenal acid and bile stimulate secretin release, in turn stimulating pancreatic bicarb secretion from ductal cells
Duodenal fat and protein stimulate CCK release, stimulating the secretion of pancreatic enzymes from acinar cells
General purpose of endocrine cells
Whole body metabolism and energy utilization
Endocrine hormone associated with alpha cells
Glucagon
Primary functions of alpha cells
Glycogenolysis
Gluconeogenesis
Lipolysis
Increase blood sugar
Endocrine hormone associated with beta cells
Insulin
Primary functions of beta cells
Glucose uptake at cellular level
Protein synthesis
Endocrine hormone associated with delta cells
Somatostatin
Primary functions of delta cells
General inhibitor of acid production, pancreatic and biliary secretion
Helps regulate pancreatic endocrine function in a paracrine manner
Characteristics of acute pancreatitis
Diffuse inflammation of the pancreas and encompasses a wide spectrum of clinical dz
_____ of cases of acute pancreatitis resolve without complications
80%
Complications of acute pancreatitis
Hemorrhage Pancreatic necrosis Infection Shock Multisystem organ failure
Goals of management of acute pancreatitis
Early dx
Supportive therapy
Tx of the underlying cause
Presentation of acute pancreatitis
Sudden onset of epigastric pain that radiates to the back, usually accompanied by nausea and vomiting
PE of acute pancreatitis
Epigastric tenderness
Retroperitoneal hemorrhage may manifest as Turner’s sign (flank ecchymosis), Cullen’s sign (periumbilical ecchymosis), or Fox’s sign (ecchymosis below the inguinal ligament and/or involving the scrotum)
Left pleural effusion may be present
A systemic inflammatory response in acute pancreatitis may lead to…
Tachycardia
Edema
Hypovolemic shock
Causes of early complications of acute pancreatitis
Usually related to massive fluid sequestration
Early complications of acute pancreatitis
Pulmonary edema
Circulatory collapse
Renal failure
Causes of late complications of acute pancreatitis
Infection or hemorrhage
What are the vast majority of causes of acute pancreatitis?
Gallstones or alcohol
What types of gallstones are likely to lead to acute pancreatitis?
Small stones <5 mm
Pathophysiology of acute pancreatitis
Autodigestion and inflammation caused by unregulated release of pancreatic enzymes within the organ
What are the end points of acute pancreatitis?
Organ edema
Peripancreatic inflammation with severe fluid loss
Multiorgan dysfunction secondary to circulating toxins
What are the primary diagnostic markers of pancreatitis?
Amylase and lipase
Difference between amylase and lipase in pancreatitis
Amylase levels peak early in the dz process and do not stay elevated beyond 5 days of ongoing inflammation
Lipase peaks later, but remains elevated for a longer period of time
Imaging in pancreatitis-plain films
May show a dilated, air-filled duodenal loop in the RUQ, focal jejunal ileus (sentinal loop sign), or transverse colonic ileus (colon cutoff sign)
Imaging in pancreatitis-abdominal u/s
Sensitivity is as low as 70%
What is the imaging modality of choice for pancreatitis?
CT scan- computerized with contrast
What are some contemporary systems for grading pancreatitis?
APACHE II Sequential Organ Failure Assessment (SOFA) Marshall Balthazar score Atlanta classification
Tx of mild acute pancreatitis
Aggressive fluid resuscitation with crystalloid solution
Correction of metabolic and electrolyte derangements
Tx of mild-moderate acute pancreatitis
In initial phase, restriction of oral intake
Consider nasogastric tube placement for ileus
Supplementary nutrition if prolonged inflammation or complications
H2 receptor antagonists or antacids for prophylaxis against upper GI tract hemorrhage in critically ill pts
When is early cholecystectomy recommended for pancreatitis?
In all cases of gallstone pancreatitis and most cases of idiopathic pancreatitis
What may be definitive therapy for pts considered too infirm to tolerate cholecystectomy for pancreatitis?
ERCP
Tx of severe acute pancreatitis
Fluid resuscitation
Apply a low threshold for invasive monitoring
Antibiotic therapy if infected pancreatic necrosis is strongly suspected or documented
Antimicrobials effective for acute pancreatitis
Imipenem 3rd gen cephalosporins Piperacillin Mezlocillin FQs Metronidazole
Three life-threatening infectious complications of acute pancreatitis
Pancreatic abscess
Infected pancreatic pseudocyst
Infected pancreatic necrosis
Cause of pancreatic infection
Most are polymicrobial and may arise from transmural migration of bacteria from adjacent inflamed bowel or from hematogenous seeding
Who is susceptible to fungal superinfection?
Pts subjected to long courses of powerful antibiotics
When should one suspect septic complications in pancreatic infection?
In pts with severe pancreatitis
Documented bacteremia
Clinical deterioration
Failure of resolution of pancreatitis within 7-10 days
Clinical manifestations of pancreatic infection
Fever
Tachycardia
Abdominal pain
Abdominal distention
