Pancreas Anatomy and Physiology

Pancreas Anatomy

• The pancreas is a retroperitoneal organ, making it difficult to diagnose its diseases.
• It is made up of the head, neck, body, and tail, with the head lying within the 'C' of the duodenum.
• The pancreas is supplied by the superior and inferior pancreaticoduodenal vessels.
• The pancreatic tail lies within the lienorenal ligament and is the only intraperitoneal part of the pancreas.

Pancreas Blood Supply

• The pancreas receives blood supply from the coeliac trunk and the superior mesenteric artery.
• The splenic artery divides into segmental branches (Majestrial 30%) or division before hilum (distributed type 70%).

Inferior Pancreatic Artery

• The inferior pancreatic artery runs along the inferior border of the pancreas and anastomoses with the splenic artery through the dorsal, great, and caudal arteries.

Pancreatic Duct Anatomy

• The main pancreatic duct of Wirsung opens at the ampulla of Vater.
• The minor pancreatic duct of Santorini opens at the minor papilla, 2cm proximal to the ampulla.

Exocrine Pancreas

• The exocrine pancreas produces enzymes such as trypsin, chymotrypsin, elastase, carboxypeptidase A, carboxypeptidase B, colipase, lipase, phospholipase A, cholesterol ester hydrolase, amylase, and ribonuclease.

Endocrine Pancreas

• The endocrine pancreas produces hormones such as insulin, glucagon, somatostatin, gastrin, VIP, and PPP.

Aetiology of Acute Pancreatitis

• Idiopathic (10-15% of cases)
• Gallstones (50-70% of cases)
• Ethanol (25%)
• Tumors, toxins, trauma, and microbiological infections
• Malnutrition, autoimmune, surgery, and hyperlipidemia
• Hereditary causes such as PRSS1 and SPINK1 genes

Drug-Induced Pancreatitis

• Antihypertensive drugs such as ACE inhibitors
• Antiarrhythmic drugs such as procainamide
• Antithyroid drugs such as carbimazole
• Anticonvulsants such as carbamazepine and sodium valproate
• Diuretics such as frusemide, thiazides, and spironolactone
• Analgesics such as NSAIDs and opiates
• Hormones such as estrogens and OCPs
• Antibiotics such as erythromycin, penicillins, cephalosporins, and tetracyclins
• Cytotoxic drugs such as L-asparaginase, azathioprine, and 6-mercaptopurine
• Anesthetics such as propofol and acetylcholinesterase inhibitors

Acute Pancreatitis - Pathophysiology

• Premature activation of trypsin leads to autodigestion of pancreatic tissue
• Activation of inflammatory response
• Inflammatory mediators cause vasodilation, shock, ARDS, MODS, and extravascular movement of serum albumin

Acute Pancreatitis - Treatment

• Management of pancreatic pseudocyst
• Endoscopic transgastric catheter drainage
• Fluoroscopic guided transgastric catheter drainage
• Laparoscopic or open cystogastrostomy, cystoduodenostomy, or cystojejunostomy
• ERCP pancreatic stenting
• Distal pancreatectomy if pseudocyst is limited to tail of pancreas
• External drainage only in abscess
• Open laparotomy is indicated in severe conditions, failed percutaneous drainage, acute abdomen, and perforation.

Chronic Pancreatitis

• Irreversible damage to the pancreas with histologic evidence of inflammation, fibrosis, and destruction of exocrine and endocrine tissue
• Aetiology:
  • Idiopathic (40%)
  • Hereditary (25%)
  • Alcoholism (15%)
  • Obstructive (stone, divisum, tumor, stricture post surgery or ERCP)
  • Hyperlipidemia (type I and V)
  • Hyperparathyroidism
  • Autoimmune
  • Nutritional

Chronic Pancreatitis - Pathophysiology

• Direct toxicity to acinar cells
• Hypoperfusion
• Increased ductal permeability
• Sphincter of Oddi spasm or dysfunction
• Increased protein secretion and plug formation
• Reduced HCO3 secretion
• Reduced trypsin inhibitor concentration
• Hyperlipidemia

Chronic Pancreatitis - Clinical Features

• Abdominal pain:
  • Continuous, intermittent, or absent
  • Involving upper abdomen or right or left hypochondrium
  • Radiating to back or chest or flank
  • Persistent, deep-seated, unresponsive to antacids
  • Worsened by alcohol intake or a heavy fatty meal
• Malabsorption with resulting steatorrhea and mineral/vitamin deficiencies

Test your knowledge on the anatomy and physiology of the pancreas, as well as the causes, symptoms, and management of acute and chronic pancreatitis. This quiz covers the objectives of a lecture on the pancreas, including its structure and functions, and the diagnosis and treatment of pancreatitis. Learn about this vital organ and its diseases. Get ready to assess your understanding!