Metabolism of Bilirubin and Hormones

Liver Functions

Synthesis and Storage:

• Liver regulates blood glucose levels through:
  • Gluconeogenesis - synthesizing glucose
  • Storing excess glucose as glycogen
• Synthesizes:
  • Fatty acids and triglycerides from excess carbohydrates
  • Lipoproteins (VLDL, HDL, LDL) for lipid transport
  • Cholesterol
  • Bile salts for digestion and absorption of lipids
  • Ketones as a consequence of excess fatty acid oxidation
• Synthesizes plasma proteins:
  • Blood clotting factors
  • Transport proteins
  • Albumin for plasma oncotic pressure
  • Complement
• Stores vitamins A, D, K, and B12, as well as iron as ferritin

Detoxification and Inactivation:

• Breaks down fat-soluble compounds through hydrolysis, oxidation, and conjugation
  • Converts them to water-soluble forms that can be excreted by the kidneys
• Used for removal of substances like testosterone, aldosterone, and bilirubin

Filtration:

• Blood from the GI tract enters the liver via the hepatic portal vein, containing nutrients, toxins, drugs, etc.
• Kupffer cells in the liver remove foreign particles like bacteria, viruses, and antigens from this blood.

Liver Anatomy

Surface Anatomy:

• Divided into right, left, and occasionally right lobe hepatic regions
• Protected by lower 6 ribs (7-12)

Ligaments:

• Coronary ligament attaches the superior surface of the liver to the diaphragm
• Triangular ligaments attach the right and left lobes to the diaphragm
• Falciform ligament attaches the anterior surface of the liver to the abdominal wall

Functional Lobes:

• Divided into 8 functional segments based on vascular supply
• Caudate and quadrate lobes on the visceral surface

Histology:

• Classic liver lobule has a central vein and portal triad at the periphery
• Portal lobule has the portal triad in the center
• Portal triad contains branches of the hepatic artery, portal vein, and bile duct

Vasculature:

• Dual blood supply:
  • Hepatic artery provides oxygenated blood
  • Hepatic portal vein provides nutrients and toxins from the GI tract
• Venous drainage via hepatic veins into the inferior vena cava

Gallbladder and Biliary Tree

• Gallbladder is a reservoir for bile, located on the visceral surface of the liver
• Cystic duct connects the gallbladder to the common hepatic duct
• Biliary tree allows bile produced by hepatocytes to drain into the duodenum

Innervation and Lymphatics

Innervation:

• Sympathetic innervation from T7-9 (celiac plexus)
• Parasympathetic innervation from the vagus nerve

Lymphatics:

• Liver lymph drains to hepatic, phrenic, and posterior mediastinal lymph nodes
• Gallbladder lymph drains to cystic and celiac nodes

Liver Problems

• Steatosis - increased fat buildup in the liver
• Steatohepatitis - inflammation of a fatty liver
• Cirrhosis - chronic liver damage leading to scarring and failure
• Hepatocellular carcinoma - liver cancer often associated with chronic viral hepatitis

Liver Biopsy

• Performed to diagnose liver conditions like abnormal liver function tests, malignancy, or fibrosis
• Procedure involves taking a small sample of liver tissue using a needle biopsy

Gallstones

• Cholelithiasis - presence of gallstones, often asymptomatic

• Cholecystitis - inflammation of the gallbladder, often causes pain

• Choledocholithiasis - gallstones in the common bile duct

• Cholangitis - infection of the bile duct, often due to choledocholithiasis### Small Intestine

• The superior part of the pancreas extends from the right crus of the diaphragm and suspends the duodenojejunal junction

• The jejunum has a larger diameter, greater surface for digestion, thicker wall, less vascular arcades, thinner mesentery with less fat, and many large, tall mucosal folds

• The ileum has a smaller diameter, smaller surface for digestion, thinner wall, more vascular arcades, thicker mesentery with more fat, and less low, sparse mucosal folds

Blood Supply and Lymphatic Drainage

• Arterial supply comes from the superior mesenteric artery, which forms jejunal and ileal branches that create arterial arcades and vasa recta
• Lymphatic drainage goes to the superior mesenteric lymph nodes, mesenteric lymph nodes, juxtaintestinal lymph nodes, and ileocolic lymph nodes

Innervation

• Sympathetic innervation comes from T9-12 and goes through the sympathetic trunks, greater, lesser, and least splanchnic nerves, and the superior mesenteric plexus, controlling pain
• Parasympathetic innervation comes from the posterior vagal trunk and controls motor function

Pancreas

• The pancreas is located in the right and left upper quadrants, epigastrium, umbilical, and left hypochondrium
• The pancreas has four divisions: head, uncinate process, neck, body, and tail
• The pancreas is retroperitoneal in position

Pancreas Features

• The main pancreatic duct is in the body and tail of the pancreas and connects to the hepaticopancreatic ampulla (of Vater) at the major duodenal papilla
• The accessory pancreatic duct is in the uncinate process and connects to the minor duodenal papilla
• The pancreatic duct has three sphincters: the sphincter of the bile duct, the sphincter of the pancreatic duct, and the hepaticopancreatic sphincter (of Odi)

Pancreas Relations

• The head of the pancreas is anterior to the transverse mesocolon, posterior to the IVC, right renal vessels, and left renal vein, and lateral, superior, and inferior to the duodenum
• The neck of the pancreas is anterior to the pylorus and posterior to the SMA/V and portal vein
• The body of the pancreas is anterior to the omental bursa and posterior to the aorta, SMA, splenic artery, L2, left suprarenal gland, left kidney, and left renal vessels
• The tail of the pancreas is posterior to the left kidney, lateral to the splenic hilum, and inferior to the left colic flexure

Pancreas Blood Supply and Lymphatics

• The body and tail of the pancreas are supplied by the splenic artery, gastroduodenal artery, and superior mesenteric artery
• The head of the pancreas is supplied by the superior and inferior pancreaticoduodenal arteries
• Lymphatic drainage goes to the pancreaticosplenic lymph nodes, pyloric lymph nodes, and superior mesenteric to hepatic to coeliac lymph nodes

Pancreas Innervation

• Parasympathetic innervation comes from the vagus nerve (CN X) and is motor
• Sympathetic innervation comes from T6-9 and goes through the superior mesenteric plexus

Pancreatic Cancer

• Pancreatic cancer typically occurs after the age of 40
• There are many types of pancreatic cancers, with ductal adenocarcinoma being the most prevalent
• Risk factors include smoking, obesity, diabetes, and others